Flowering and Runnering of Seasonal Strawberry under Different Photoperiods Are Affected by Intensity of Supplemental or Night-Interrupting Blue Light

The strawberry (Fragaria × ananassa Duch.) "Sulhyang" is a typical seasonal flowering (SF) strawberry that produces flower buds in day lengths shorter than a critical limit (variable, but often defined as <12 h). There is a trade-off between photoperiod-controlled flowering and gibberellin (GA) signaling pathway-mediated runnering. Some related genes (such as CO, FT1, SOC1, and TFL1) participating in light signaling and circadian rhythm in plants are altered under blue light (BL). Sugars for flowering and runnering are mainly produced by photosynthetic carbon assimilation. The intensity of light could affect photosynthesis, thereby regulating flowering and runnering. Here, we investigated the effect of the intensity of supplemental blue light (S-BL) or night-interrupting blue light (NI-BL) in photoperiodic flowering and runnering regulation by applying 4 h of S-BL or NI-BL with either 0, 10, 20, 30, or 40 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) in a 10 h short-day (SD10) (SD10 + S-BL4 or + NI-BL4 (0, 10, 20, 30, or 40)) or 14 h long-day (LD14) conditions (LD14 + S-BL4 or + NI-BL4 (0, 10, 20, 30, or 40)). Approximately 45 days after the photoperiodic light treatment, generally, whether S-BL or NI-BL, BL (20) was the most promotive in runnering, leading to more runners in both the LD and SD conditions. For flowering, except the treatment LD14 + S-BL, BL (20) was still the key light, either from BL (20) or BL (40), promoting flowering, especially when BL acted as the night-interrupting light, regardless of the photoperiod. At the harvest stage, larger numbers of inflorescences and runners were observed in the LD14 + NI-BL4 treatment, and the most were observed in the LD14 + NI-BL (20). Moreover, the SD10 + NI-BL4 was slightly inferior to the LD14 + NI-BL4 in increasing the numbers of inflorescences and runners, but it caused earlier flowering. Additionally, the circadian rhythm expression of flowering-related genes was affected differently by the S-BL and NI-BL. After the application of BL in LD conditions, the expression of an LD-specific floral activator FaFT1 was stimulated, while that of a flowering suppressor FaTFL1 was inhibited, resetting the balance of expression between these two opposite flowering regulators. The SD runnering was caused by BL in non-runnering SD conditions associated with the stimulation of two key genes that regulate runner formation in the GA pathway, FaGRAS32 and FaGA20ox4. In addition, the positive effects of BL on enhancing photosynthesis and carbohydrate production also provided an abundant energy supply for the flowering and runnering processes.

Exploring the potential: Can arsenic (As) resistant silicate-solubilizing bacteria manage the dual effects of silicon on As accumulation in rice?

Rice (Oryza sativa L.) cultivation in regions marked by elevated arsenic (As) concentrations poses significant health concerns due to As uptake by the plant and its subsequent entry into the human food chain. With rice serving as a staple crop for a substantial share of the global population, addressing this issue is critical for food security. In flooded paddy soils, where As availability is pronounced, innovative strategies to reduce As uptake and enhance agricultural sustainability are mandatory. Silicon (Si) and Si nanoparticles have emerged as potential candidates to mitigate As accumulation in rice. However, their effects on As uptake exhibit complexity, influenced by initial Si levels in the soil and the amount of Si introduced through fertilization. While low Si additions may inadvertently increase As uptake, higher Si concentrations may alleviate As uptake and toxicity. The interplay among existing Si and As availability, Si supplementation, and soil biogeochemistry collectively shapes the outcome. Adding water-soluble Si fertilizers (e.g., Na2SiO3 and K2SiO3) has demonstrated efficacy in mitigating As toxicity stress in rice. Nonetheless, the expense associated with these fertilizers underscores the necessity for low cost innovative solutions. Silicate-solubilizing bacteria (SSB) resilient to As hold promise by enhancing Si availability by accelerating mineral dissolution within the rhizosphere, thereby regulating the Si biogeochemical cycle in paddy soils. Promoting SSB could make cost-effective Si sources more soluble and, consequently, managing the intricate interplay of Si's dual effects on As accumulation in rice. This review paper offers a comprehensive exploration of Si's nuanced role in modulating As uptake by rice, emphasizing the potential synergy between As-resistant SSB and Si availability enhancement. By shedding light on this interplay, we aspire to shed light on an innovative attempt for reducing As accumulation in rice while advancing agricultural sustainability.

Top and Side Lighting Induce Morphophysiological Improvements in Korean Ginseng Sprouts (Panax ginseng C.A. Meyer) Grown from One-Year-Old Roots

Nowadays, not only the roots, but also leaves and flowers of ginseng are increasingly popular ingredients in supplements for healthcare products and traditional medicine. The cultivation of the shade-loving crop, ginseng, is very demanding in terms of the light environment. Along with the intensity and duration, light direction is another important factor in regulating plant morphophysiology. In the current study, three lighting directions-top (T), side (S), or top + side (TS)-with an intensity of 30 ± 5 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) were employed. Generally, compared with the single T lighting, the composite lighting direction, TS, was more effective in shaping the ginseng with improved characteristics, including shortened, thick shoots; enlarged, thick leaves; more leaf trichomes; earlier flower bud formation; and enhanced photosynthesis. The single S light resulted in the worst growth parameters and strongly inhibited the flower bud formation, leading to the latest flower bud observation. Additionally, the S lighting acted as a positive factor in increasing the leaf thickness and number of trichomes on the leaf adaxial surface. However, the participation of the T lighting weakened these traits. Overall, the TS lighting was the optimal direction for improving the growth and development traits in ginseng. This preliminary research may provide new ideas and orientations in ginseng cultivation lodging resistance and improving the supply of ginseng roots, leaves, and flowers to the market.

Difference between Day and Night Temperature (DIF) and Light Intensity Affect Growth and Photosynthetic Characteristics of Panax ginseng Meyer Sprouts

Panax ginseng sprouts (PGS) have the advantage of requiring short-term cultivation while maintaining higher ginsenoside contents than traditional ginseng seedlings. It is feasible to improve their yield capacity by manipulating physical factors such as temperature and light. This study therefore investigated the effects of the DIF (difference between day and night temperature) and LI (light intensity) on the growth and photosynthetic characteristics of PGS. To this end, four DIF treatments (18/22 °C, 20/20 °C, 22/22 °C, 22/18 °C), corresponding to two LI regimes (20 PPFD, 200 PPFD), were applied on one-year-old ginseng rootlets in closed-type plant production systems (CPPSs). The PGS had distinctly different responses to the eight treatments. In particular, we found that negative DIF considerably hampered the growth and development of roots, shoots, leaves, and photosynthesis, regardless of the LI considered. The PGS treated with 20/20 °C combined with 20 PPFD displayed the best root growth, shoot development, leaf area, as well as optimal photosynthetic ability. On the other hand, we further showed that the root growth rate was positively correlated with the stem diameter, leaf traits, and photosynthetic ability, whereas it was negatively correlated with the petiole length, stem length, and shoot length. Collectively, 20/20 °C combined with 20 PPFD was the optimal condition in the current study, and may be regarded as a successful strategy for large-scale productions of PGS.

Shift in the Light Quality of Night Interruption Affects Flowering and Morphogenesis of Petunia hybrida

Petunia hybrida Hort. "Easy Wave Pink", a qualitative long-day plant (LDP), was investigated to study the effects of the night interruption light (NIL) provided by light-emitting diodes (LEDs) quality shifting on the morphogenesis, blooming, and transcription of photoreceptor genes. Plants were grown in a closed-type plant factory employing white (W) LEDs at an intensity of 180 μmol·m-2·s-1 PPFD provided for short day (SD, 10 h light, 14 h dark), long day (LD, 16 h light, 8 h dark), or SD with 4 h night interruption (NI) with LEDs at an intensity of 10 μmol·m-2·s-1 PPFD. The NIL quality was shifted from one light spectrum to another after the first 2 h of NI. Light treatments consisting of all possible pairings of W, far-red (Fr), red (R), and blue (B) light were tested. The SD and LD were referenced as the control, while 12 NI treatments involved altering LED NIL qualities, as follows: from R to B (NI-RB), from B to R (NI-BR), from Fr to R (NI-FrR), from R to Fr (NI-RFr), from Fr to B (NI-FrB), from B to Fr (NI-BFr), from B to W (NI-BW), from W to B (NI-WB), from W to Fr (NI-WFr), from Fr to W (NI-FrW), from W to R (NI-WR), and from R to W (NI-RW). The NI-RFr resulted in the longest shoots, while the NI-WR and NI-RW resulted in the shortest shoots. NI-WR, NI-RW, NI-BW, NI-WB, NI-RFr, NI-RB, NI-BR, and LD all exhibited flowering. High-level expressions of photoreceptor genes were confirmed in the NI-RFr, NI-FrR, NI-BFr, NI-RW, and NI-WR treatments. Morphogenesis and blooming were both impacted by the photoperiod. The first NIL had no effects on the flowering or the morphogenesis, but the second NIL had a profound impact on both.

Arsenic (As) resistant bacteria with multiple plant growth-promoting traits: Potential to alleviate As toxicity and accumulation in rice

A currently serious agronomic concern for paddy soils is arsenic (As) contamination. Paddy soils are mostly utilized for rice cultivation. Arsenite (As(III)) is prevalent in paddy soils, and its high mobility and toxicity make As uptake by rice substantially greater than that by other food crops. Globally, interest has increased towards using As-resistant plant growth-promoting bacteria (PGPB) to improve plant metal tolerance, promote plant growth, and immobilize As to prevent its uptake and accumulation in the edible parts of rice as much as possible. This review focuses on the As-resistant PGPB characteristics influencing rice growth and the mechanisms by which they function to alleviate As toxicity stress in rice plants. Several recent examples of mechanisms responsible for decreasing the availability of As to rice and coping with As stresses facilitated by the PGPB with multiple PGP traits (e.g., phosphate and silicate solubilization, the production of 1-aminocyclopropane-1-carboxylate deaminase, phytohormones, and siderophore, N₂ fixation, sulfate reduction, the biosorption, bioaccumulation, methylation, and volatilization of As, and arsenite oxidation) are also reviewed. In addition, future research needs about the application of As-resistant PGPB with PGP traits to mitigate As accumulation in rice plants are described.

Blue Light Supplemented at Intervals in Long-Day Conditions Intervenes in Photoperiodic Flowering, Photosynthesis, and Antioxidant Properties in Chrysanthemums

The flowering of chrysanthemum (Chrysanthemum morifolium Ramat.), inhibited by long-day lighting, can be reversed with a short period of low supplemental blue light (S-BL). Both flowering and the reactive oxygen species (ROS) scavenging processes are primarily driven by sugars created by photosynthetic carbon assimilation. In addition, the antioxidant ability potentially affects flowering in photoperiod- and/or circadian rhythm-dependent manners. This indicates that there is an interactive relationship among blue (B) light, photosynthetic efficiency, sugar accumulation, and antioxidant ability in flowering regulation. Here, 4 h of 30 μmol·m^-2·s^-1 photosynthetic photon flux density (PPFD) S-BL was applied at the end of a 13-h long-day period (LD13 + 4B) at different intervals during 60 days of experimental duration. The five experimental groups were named according to the actual number of days of S-BL and their intervals: applied once every day, "60 days-(LD13 + 4B) (100.0%)"; once every other day, "30 days-(LD13 + 4B) (50.0%)"; once every three days, "15 days-(LD13 + 4B) (25.0%)"; once every five days, "10 days-(LD13 + 4B) (16.7%)"; and once every seven days, "7 days-(LD13 + 4B) (11.7%)". Two non-S-BL control groups were also included: 60 10-h short days (60 days-SD10) and 13-h long days (60 days-LD13). At the harvest stage, varying degrees of flowering were observed except in "60 days-LD13" and "7 days-(LD13 + 4B) (11.7%)". The number of flowers increased and the flower buds appeared earlier as the proportion of S-BL days increased in LD13 conditions, although the "60 days-SD10" gave the earliest flowering. The proportion of initial, pivotal, and optimal flowering was 16.7% ("10 days-(LD13 + 4B)"), 50.0% ("30 days-(LD13 + 4B)"), and 100.0% ("60 days-(LD13 + 4B)"), respectively. Meanwhile, a series of physiological parameters such as the production of enzymatic or non-enzymatic antioxidants, chlorophyll content, photosynthetic efficiency, enzyme activities, and carbohydrate accumulation were significantly improved by "30 days-(LD13 + 4B) (50.0%)" as a turning point until the peaks appeared in "60 days-(LD13 + 4B) (100.0%)", as well as the expression of florigenic or anti-florigenic and some antioxidant-synthetic genes. Furthermore, the results of principal component analysis (PCA) indicated that S-BL days positively regulated flowering, photosynthesis, carbohydrate accumulation, and antioxidant production. In aggregate, the pivotal and optimal proportions of S-BL days to reconcile the relationship among flowering, photosynthetic carbon assimilation, and antioxidant ability were 50.0% and 100.0%, respectively. However, there are still significant gaps to be filled in order to determine the specific involvement of blue light and antioxidant abilities in flowering regulation.

Silicon Supplementation Alleviates Adverse Effects of Ammonium on Ssamchoo Grown in Home Cultivation System

Ssamchoo is recently attracting attention as a household hydroponic vegetable in Korea. It has a refreshing texture and a rich content of vitamins and fiber. Ssamchoo with a wide leaf area is suitable for traditional ssam or vegetable wraps, as well as a vegetable for salads; thus, it can be used in a variety of dishes. However, Ssamchoo plants responds sensitively to the nutrient solution, and it is often difficult to secure sufficient leaf area and robust growth using a commercial nutrient solution for leafy vegetables. This study consisted of three experiments conducted to develop the nutrient solution for Ssamchoo grown in a newly developed home hydroponic cultivation system using light-emitting diodes as the sole source of light. In the first experiment, growth and development of Ssamchoo in a representative commercial nutrient solution, Peters Professional (20-20-20, The Scotts Co., Marysville, OH, USA), was compared with laboratory-prepared nutrient solutions, GNU1 and GNU2. As a result, the Ssamchoo grown in Peters Professional had a high NH₄⁺ content in the tissue, leaf yellowing, darkened root color, and suppressed root hair development. In addition, adverse effects of ammonium such as low fresh weight and shorter shoot length were observed. In the second experiment, Peters Professional was excluded, and the ratio of NO₃^- to NH₄⁺ in the GNU1 and GNU2 nutrient solutions was set to four levels each (100:0, 83.3:16.7, 66.7:33.3, and 50:50). As a result, the fresh weights of 83.3:16.7 and 66.7:33.3 were the greatest, and the leaf color was a healthy green. However, at 100:0 and 50:50 NO₃^-/NH₄⁺ ratios, the fresh weight was low, and leaf yellowing, tip burn, and leaf burn appeared. The nutrient solution with a 83.3:16.7 NO₃^-- to-NH₄⁺ ratio, which gave the greatest fresh weight in the second experiment, was chosen as the control, while the solution with a 50:50 NO₃^-/NH₄⁺ ratio with a lower nitrate content among the two unfavorable treatments was selected as a treatment group for the next experiment. In the third experiment, NH₄⁺ was partially replaced with urea to make four different ratios of NO₃^- to NH₄⁺ to urea (83:17:0, 50:50:0, 50:25:25, and 50:0:50) in combination with two levels of Si (0 and 10.7 mmol·L^-1 Si). The greatest fresh weight was obtained in the treatment in which the NO₃^-/NH₄⁺/urea ratio was 50:25:25. In particular, when Si was added to the solution, there was no decrease in the number of leaves, and plants with the greatest fresh weight, chlorophyll content, and leaf area were obtained. The number of leaves and leaf area are important indicators of high productivity since the Ssamchoo is used in ssam dishes. It can be concluded that a solution with a NO₃^-/NH₄⁺/urea ratio of 50:25:25 and supplemented with 10.7 mmol·L^-1 Si is the most suitable nutrient solution for growing Ssamchoo in the home hydroponic system developed.

The flowering of SDP chrysanthemum in response to intensity of supplemental or night-interruptional blue light is modulated by both photosynthetic carbon assimilation and photoreceptor-mediated regulation

The photoreceptor-mediated photoperiodic sensitivity determines the obligate short-day flowering in chrysanthemum (Chrysanthemum morifolium Ramat.) when the night length is longer than a critical minimum, otherwise, flowering is effectively inhibited. The reversal of this inhibition by subsequent exposure to a short period of supplemental (S) or night-interruptional (NI) blue (B) light (S-B; NI-B) indicates the involvement of B light-received photoreceptors in the flowering response. Flowering is mainly powered by sugars produced through photosynthetic carbon assimilation. Thus, the light intensity can be involved in flowering regulation by affecting photosynthesis. Here, it is elucidated that the intensity of S-B or NI-B in photoperiodic flowering regulation of chrysanthemums by applying 4-h of S-B or NI-B with either 0, 10, 20, 30, or 40 μmol·m^-2·s^-1 photosynthetic photon flux density (PPFD) in a 10-h short-day (SD10) [SD10 + 4B or + NI-4B (0, 10, 20, 30, or 40)] or 13-h long-day (LD13) condition [LD13 + 4B or + NI-4B (0, 10, 20, 30, or 40)] provided by 300 ± 5 μmol·m^-2·s^-1 PPFD white (W) LEDs. After 60 days of photoperiodic light treatments other than the LD13 and LD13 + NI-4B (40), flowering with varying degrees was observed, although the SD10 gave the earliest flowering. And the LD13 + 4B (30) produced the greatest number of flowers. The flowering pattern in response to the intensity of S-B or NI-B was consistent as it was gradually promoted from 10 to 30 μmol m^-2 s^-1 PPFD and inhibited by 40B regardless of the photoperiod. In SD conditions, the same intensity of S-B and NI-B did not significantly affect flowering, while differential flowering inhibition was observed with any intensity of NI-B in LDs. Furthermore, the 30 μmol·m^-2·s^-1 PPFD of S-B or NI-B up-regulated the expression of floral meristem identity or florigen genes, as well as the chlorophyll content, photosynthetic efficiency, and carbohydrate accumulation. The 40B also promoted these physiological traits but led to the unbalanced expression of florigen or anti-florigen genes. Overall, the photoperiodic flowering in response to the intensity of S-B or NI-B of the SDP chrysanthemum suggests the co-regulation of photosynthetic carbon assimilation and differential photoreceptor-mediated control.

Alleviation of Ammonium Toxicity in Salvia splendens ‘Vista Red’ with Silicon Supplementation

Ammonium (NH₄⁺) toxicity seriously hampers the yield and quality of salvia plants because most varieties or sub-species are highly sensitive to NH₄⁺. Silicon (Si) is an alternative that is used to minimize these disturbances and maintain better growth under NH₄⁺ toxicity. Nevertheless, the mitigatory effects of Si on NH₄⁺-stressed salvia are unknown. Therefore, this study was carried out to determine how Si assists to alleviate the NH₄⁺ toxicity degree in salvia. To this end, salvia plants were cultivated in a controlled environment supplied with a constant N (nitrogen) level (13 meq·L⁻¹) in the form of three NH₄⁺:NO₃⁻ ratios (0:100, 50:50, 100:0), each with (1.0 meq·L⁻¹) or without Si. Physiological disorders and typical NH₄⁺ toxicity symptoms, as well as interrupted photosynthesis, were observed in the 100% NH₄⁺-treated plants. Furthermore, cation uptake inhibition and oxidative damage were also imposed by the 100% NH₄⁺ supply. In contrast, in the presence of Si, the NH₄⁺ toxicity degree was attenuated and plant growth was ensured. Accordingly, the NH₄⁺ toxicity appearance ratio decreased significantly. Furthermore, Si-treated plants showed an ameliorated photosynthetic ability, elevated internal K and Ca levels, and enhanced antioxidative capacity, as reflected by improved major antioxidant enzyme activities, as well as diminished accumulation of ROS (reactive oxygen species) and MDA (malondialdehyde). Our findings enlightened the agronomic importance of additional Si to nutrient solutions, especially pertaining to bedding plants at risk of NH₄⁺ toxicity.

Foliar Silicon Spray to Strawberry Plants During Summer Cutting Propagation Enhances Resistance of Transplants to High Temperature Stresses

Silicon (Si) has been reported to benefit plant growth and stress resistance. This work aimed to find out an optimal method of Si application to enhance the resistance of strawberry (Fragaria × ananassa Duch.) transplants to high temperatures, commonly experienced in the summer when strawberries are propagated for greenhouse production in Korea. Plants of strawberry “Sulhyang”, “Maehyang”, and “Kuemsil” were subjected to one of five treatments before the cutting propagation: no treatment (control), substrate dressing of a water-soluble silicate fertilizer, substrate drench of 75 mg·L−1 Si (from potassium silicate) to the mother plants, or foliar spray of 75 mg·L−1 Si to either the mother plants or daughter plants. Half of the daughter plants in each Si treatment received continued application of Si through either substrate dressing of a water-soluble silicate fertilizer, substrate drench, or foliar spray after the cutting propagation. A high temperature (43°C) resistance test was conducted in plant growth chambers for 7 days with a 16-h photoperiod with a light intensity of 300 mmol·m−2·s−1 PPFD. During the high temperature test, the rate of decline in the photosynthesis was lower in plants treated with Si than in the control. After the high temperature test, it was observed that Si application significantly increased the shoot fresh weight of transplants. Moreover, the contents of sugars, proteins, and enzymatic (CAT, SOD, POD, and APX) and non-enzymatic (anthocyanin and proline) antioxidants were higher in plants treated with Si throughout the entire propagation period, compared to the control and plants only treated with Si before or after the cutting propagation. Overall, the Si application improved the growth of the transplants regardless of the application method used. Moreover, spraying the daughter plants with Si, and continually spraying the transplants were found to be the best and is recommended to increase the resistance of strawberries to high temperatures during propagation.

Silicon Mitigates Ammonium Toxicity in Cabbage (Brassica campestris L. ssp. pekinensis) ‘Ssamchu’

Ammonium (NH4+) toxicity hinders the cabbage yield because most subspecies or varieties exhibit extreme sensitivity to NH4+. Current knowledge indicates that silicon (Si) can alleviate or reverse the ammonium toxicity severity. However, few investigations have been conducted on NH4+-stressed cabbage to elucidate the mechanism underlying the Si alleviation. The study described herein analyzes induced physio-chemical changes to explore how Si helps mitigate NH4+ toxicity. We applied one of three NH4+:NO3- ratios (0:100, 50:50, and 100:0) at a constant N (13 meq·L−1) to the cabbage plants, corresponding with two Si treatment levels (0 and 1.0 meq·L−1). Chlorosis and foliage necrosis along with stunted roots occurred following 100% NH4+ application were ameliorated in the presence of Si. The NH4+ toxicity ratio was reduced accordingly. Similarly, inhibition on the uptake of K and Ca, restricted photosynthesis (chlorophyll, stomatal conductance, and Fv/Fm), and accumulation of reactive oxygen species (ROS, O2·-, and H2O2), as well as lipid peroxidation (MDA, malondialdehyde) in NH4+-stressed cabbages were mitigated with added Si. The lower observed oxidative stresses in solely NH4+-treated plants were conferred by the boosted antioxidant enzymes (SOD, superoxide dismutase; CAT, catalase). Concomitantly, Si-treated plants showed higher activities of key NH4+ assimilation enzymes (GS, glutamine synthetase; GOGAT, glutamate synthase; NADH-GDH, glutamate dehydrogenase) and NH4+ content in leaves. However, excessive NH4+ assimilations cause the acidic stress, which has been demonstrated to be the primary cause of NH4+ toxicity. Therefore, further investigation regarding the Si effects on H+ regulation and distribution should be warranted.

Low-Intensity Blue Light Supplemented during Photoperiod in Controlled Environment Induces Flowering and Antioxidant Production in Kalanchoe

Kalanchoe (Kalanchoe blossfeldiana) is a qualitative short-day plant with a high aesthetic value. When the night length is less than a specified cultivar-dependent critical value, however, it does not develop flowers. This study investigated the effects of low-intensity supplementary or night interrupting (NI) blue (B) light on the plant performance and flower induction in kalanchoe ‘Rudak’. During the photoperiod in a closed-type plant factory with day/night temperatures of 23 °C/18 °C, white (W) LEDs were utilized to produce a photosynthetic photon flux density (PPFD) of 300 μmol m⁻² s⁻¹, and B LEDs were used to give supplementary/NI light at a PPFD of 10 μmol m⁻² s⁻¹. The control plants were exposed to a 10-h short day (SD, positive control) or a 13-h long day (LD, negative control) treatment without any B light. The B light was used for 4 h either (1) to supplement the W LEDs at the end of the SD (SD + 4B) and LD (LD + 4B), or (2) to provide night interruption (NI) in the SD (SD + NI-4B) and LD (LD + NI-4B). The LD + 4B and LD + NI-4B significantly enhanced plant growth and development, followed by the SD + 4B and SD + NI-4B treatments. In addition, the photosynthesis, physiological parameters, and activity of antioxidant systems were improved in those treatments. Except in the LD and LD + NI-4B, all plants flowered. It is noteworthy that kalanchoe ‘Rudak’ flowered in the LD + 4B treatment and induced the greatest number of flowers, followed by SD + NI-4B and SD + 4B. Plants grown in the LD + 4B treatment had the highest expression levels of certain monitored genes related to flowering. The results indicate that a 4-h supplementation of B light during the photoperiod in both the SD and LD treatments increased flower bud formation, promoted flowering, and enhanced plant performance. Kalanchoe ‘Rudak’ flowered especially well in the LD + 4B, presenting a possibility of practically inducing flowering in long-day seasons with B light application.

Seleno-Amino Acids in Vegetables: A Review of Their Forms and Metabolism

Seleno-amino acids are safe, health-promoting compounds for humans. Numerous studies have focused on the forms and metabolism of seleno-amino acids in vegetables. Based on research progress on seleno-amino acids, we provide insights into the production of selenium-enriched vegetables with high seleno-amino acids contents. To ensure safe and effective intake of selenium, several issues need to be addressed, including (1) how to improve the accumulation of seleno-amino acids and (2) how to control the total selenium and seleno-amino acids contents in vegetables. The combined use of plant factories with artificial lighting and multiple analytical technologies may help to resolve these issues. Moreover, we propose a Precise Control of Selenium Content production system, which has the potential to produce vegetables with specified amounts of selenium and high proportions of seleno-amino acids.

Root GS and NADH-GDH Play Important Roles in Enhancing the Ammonium Tolerance in Three Bedding Plants

Ammonium is a paradoxical nutrient because it is more metabolically efficient than nitrate, but also causes plant stresses in excess, i.e., ammonium toxicity. Current knowledge indicates that ammonium tolerance is species-specific and related to the ammonium assimilation enzyme activities. However, the mechanisms underlying the ammonium tolerance in bedding plants remain to be elucidated. The study described herein explores the primary traits contributing to the ammonium tolerance in three bedding plants. Three NH4+:NO3− ratios (0:100, 50:50, 100:0) were supplied to salvia, petunia, and ageratum. We determined that they possessed distinct ammonium tolerances: salvia and petunia were, respectively, extremely sensitive and moderately sensitive to high NH4+ concentrations, whereas ageratum was tolerant to NH4+, as characterized by the responses of the shoot and root growth, photosynthetic capacity, and nitrogen (amino acid and soluble protein)-carbohydrate (starch) distributions. An analysis of the major nitrogen assimilation enzymes showed that the root GS (glutamine synthetase) and NADH-GDH (glutamate dehydrogenase) activities in ageratum exhibited a dose-response relationship (reinforced by 25.24% and 6.64%, respectively) as the NH4+ level was raised from 50% to 100%; but both enzyme activities were significantly diminished in salvia. Besides, negligible changes of GS activities monitored in leaves revealed that only the root GS and NADH-GDH underpin the ammonium tolerances of the three bedding plants.

Effectiveness of plants and green infrastructure utilization in ambient particulate matter removal

Air pollution is regarded as an increasingly threatening, major environmental risk for human health. Seven million deaths are attributed to air pollution each year, 91% of which is due to particulate matter. Vegetation is a xenobiotic means of removing particulate matter. This review presents the mechanisms of PM capture by plants and factors that influence PM reduction in the atmosphere. Vegetation is ubiquitously approved as a PM removal solution in cities, taking various forms of green infrastructure. This review also refers to the effectiveness of plant exploitation in GI: trees, grasslands, green roofs, living walls, water reservoirs, and urban farming. Finally, methods of increasing the PM removal by plants, such as species selection, biodiversity increase, PAH-degrading phyllospheric endophytes, transgenic plants and microorganisms, are presented.

Contribution of Arbuscular Mycorrhizal Fungi, Phosphate-Solubilizing Bacteria, and Silicon to P Uptake by Plant

Phosphorus (P) availability is usually low in soils around the globe. Most soils have a deficiency of available P; if they are not fertilized, they will not be able to satisfy the P requirement of plants. P fertilization is generally recommended to manage soil P deficiency; however, the low efficacy of P fertilizers in acidic and in calcareous soils restricts P availability. Moreover, the overuse of P fertilizers is a cause of significant environmental concerns. However, the use of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB), and the addition of silicon (Si) are effective and economical ways to improve the availability and efficacy of P. In this review the contributions of Si, PSB, and AMF in improving the P availability is discussed. Based on what is known about them, the combined strategy of using Si along with AMF and PSB may be highly useful in improving the P availability and as a result, its uptake by plants compared to using either of them alone. A better understanding how the two microorganism groups and Si interact is crucial to preserving soil fertility and improving the economic and environmental sustainability of crop production in P deficient soils. This review summarizes and discusses the current knowledge concerning the interactions among AMF, PSB, and Si in enhancing P availability and its uptake by plants in sustainable agriculture.

Comparative physiological and proteomic analysis deciphering tolerance and homeostatic signaling pathways in chrysanthemum under drought stress

Drought is increasing prevalently, mostly due to global warming, and harmful effects associated with drought stress include a reduction in the developmental phases of the plant life cycle. Drought stress affects vital metabolic processes in plants such as transpiration, photosynthesis and respiration. The other physiological and cellular processes like protein denaturation and aggregation are also affected by drought. Drought stress severely affects the floral industry by reducing the yield of flowers and among them is chrysanthemum (Dendranthema grandiflorum). In this study, we determined the critical signaling pathways, tolerance mechanism and homeostatic maintenance to drought stress in chrysanthemum. We compared the proteome of chrysanthemum leaves under drought stress. Among 250 proteins on 2DE gels, 30 protein spots were differentially expressed. These proteins were involved in major signaling pathways including, stress response, flower development and other secondary metabolism like physiological transport, circadian rhythm, gene regulation, DNA synthesis and protein ubiquitination. A reduction in a biomass, flower development, photosynthesis, transpiration, stomatal conductance, PSII yield and stomatal index was also observed in our results. Moreover, the stress markers and leaf water potential were also analyzed to depict the level of stress tolerance in chrysanthemum. Our data suggested that chrysanthemum plants developed reactive oxygen species and revealed signaling pathways to cope with drought stress. These results, thus, provide crucial information about how chrysanthemum plants respond to drought stress to maintain homeostasis.

Lighting Direction Affects Leaf Morphology, Stomatal Characteristics, and Physiology of Head Lettuce (Lactuca sativa L.)

Plants are exposed to numerous biotic and abiotic stresses, and light is one of the most important factors that influences the plant morphology. This study was carried out to examine how the lighting direction affected the plant morphology by investigating the growth parameters, epidermal cell elongation, stomatal properties, and physiological changes. Seedlings of two head lettuce (Lactuca sativa L.) cultivars, Caesar Green and Polla, were subjected to a 12 h photoperiod with a 300 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) provided by light emitting diodes (LEDs) from three directions: the top, side, and bottom, relative to the plants. Compared with the top and side lighting, the bottom lighting increased the leaf angle and canopy by stimulating the epidermal cell elongation in leaf midrib, reduced the leaf number and root biomass, and induced large stomata with a low density, which is associated with reduced stomatal conductance and carbohydrate contents. However, the proline content and quantum yield exhibited no significant differences with the different lighting directions in both cultivars, which implies that the plants were under normal physiological conditions. In a conclusion, the lighting direction had a profound effect on the morphological characteristics of lettuce, where the plants adapted to the changing lighting environments.

Effect of Iron Source and Medium pH on Growth and Development of Sorbus commixta In Vitro

Sorbus commixta is a valuable hardwood plant with a high economical value for its medicinal and ornamental qualities. The aim of this work was to investigate the effects of the iron (Fe) source and medium pH on the growth and development of S. commixta in vitro. The Fe sources used, including non-chelated iron sulfate (FeSO₄), iron ethylenediaminetetraacetic acid (Fe-EDTA), and iron diethylenetriaminepentaacetic acid (Fe-DTPA), were supplemented to the Multipurpose medium with a final Fe concentration of 2.78 mg·L^-1. The medium without any supplementary Fe was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70. The experiment was conducted in a culture room for six weeks with 25 °C day and night temperatures, and a 16-h photoperiod with a light intensity of 50 mmol·m^-2·s^-1 photosynthetic photon flux density (PPFD). Both the Fe source and pH affected the growth and development of the micropropagated plants in vitro. The leaves were greener in the pH 4.70 and 5.70 treatments. The tissue Fe content decreased with the increase of the medium pH. The leaf chlorophyll content was similar between plants treated with FeSO₄ and those with Fe-EDTA. The numbers of the shoots and roots of plantlets treated with FeSO₄ were 2.5 and 2 times greater than those of the control, respectively. The fresh and dry weights of the shoot and the root were the greatest for plants treated with Fe-EDTA combined with pH 5.70. The calcium, magnesium, and manganese contents in the plantlets increased in the pH 5.70 treatments regardless of the Fe source. Supplementary Fe decreased the activity of ferric chelate reductase. Overall, although the plantlets absorbed more Fe at pH 4.70, Fe-EDTA combined with pH 5.70 was found to be the best for the growth and development of S. commixta in vitro.

Quality of Supplementary Morning Lighting (SML) During Propagation Period Affects Physiology, Stomatal Characteristics, and Growth of Strawberry Plants

Artificial light supplementation is widely used in modern agriculture. Due to their numerous advantages, light emitting diodes (LEDs) are widely used to effectively increase the yield or control the development of crops. In the present study, the effects of supplementary morning lighting (SML) with LEDs on the physiology and stomatal characteristics of strawberry plants were studied, with the aim of awakening the plant guard cells before sunrise and enabling strawberry plants to efficiently photosynthesize immediately after sunrise. Young daughter plants of 'Maehyang' and 'Seolhyang' strawberry cultivars that have just rooted were grown under LEDs with different wavelengths-white (W), red (R), mixed blue and red (BR, 1:1), and blue (B)-to investigate the effects of the SML on the physiology, stomatal characteristics, and growth. The SML was provided for 2 h at an intensity of 100 μmol·m-2·s-1 PPFD before sunrise every morning. A group without supplementary lighting was set as the control. The results showed that the different SML qualities have significantly affected the stomatal characteristics. The B SML promoted the stomatal opening more effectively compared to the other SMLs. The stomatal conductance and quantum yield (Fv/Fm) of leaves treated with the SMLs were higher than those of the control group. The B and BR SMLs most significantly affected the stomatal conductance and quantum yield (Fv/Fm). After 30 days of the SML treatments, it was observed that the B SML effectively improved the plant quality, chlorophyll content, and carbohydrate accumulation in the two strawberry cultivars. In general, a short-term exposure to blue light before sunrise can effectively improve the quality and promote the production of strawberry plants.

Synergistic Effect of NaCl Pretreatment and PVP on Browning Suppression and Callus Induction from Petal Explants of Paeonia Lactiflora Pall. 'Festival Maxima'

Browning is prevalent in tissue cultures of Paeonia lactiflora Pall. (herbaceous peony), and severely affects and restricts the growth and differentiation of the explants. In this study, dipping excised explants in a sodium chloride (NaCl) solution as a pretreatment, adding polyvinyl pyrrolidone (PVP) to the culture medium, storing planted explants at 4 °C for 24 h, and transferring planted explants to a new medium after 24 h were considered as browning-suppression methods in tissue cultures of herbaceous peony 'Festival Maxima'. The treated petal explants were cultured in a culture room with a 16-hour photoperiod, 25 °C temperature, and 80% relative humidity in darkness for 4 to 8 weeks. The results demonstrated that dipping excised explants in a 0.5 g·L-1 NaCl solution, adding 0.5 g·L-1 PVP to the medium, storing planted explants at 4 °C for 24 h, and transferring planted explants to the same fresh medium after 24 h could effectively inhibit browning. Adding PVP to the medium led to the greatest browning suppression percentage of 95%. Storing planted explants at 4 °C for 24 h reduced the effectiveness of other treatments in suppressing browning. After 8 weeks, dipping excised explants in a NaCl solution resulted in the highest callus induction percentage of 75%, while storing explants at 4 °C for 24 h suppressed callus formation. It was observed in all treatments that decreases in browning was accompanied with higher levels of phenols and lower activities of phenylalanine ammonia-lyase (PAL) and polyphenoloxidase (PPO). Overall, the results suggest that dipping in a NaCl solution was effective in alleviating the browning issues of herbaceous peony tissue cultures, and had positive synergistic effects with PVP on browning suppression and callus induction.

Physiological and Proteomic Insights Into Red and Blue Light-Mediated Enhancement of in vitro Growth in Scrophularia kakudensis-A Potential Medicinal Plant

The current study has determined the effect of red and blue lights on the enhancement of growth, antioxidant property, phytochemical contents, and expression of proteins in Scrophularia kakudensis. In vitro-grown shoot tip explants of S. kakudensis were cultured on the plant growth regulator-free Murashige and Skoog (MS) medium and cultured under the conventional cool white fluorescent lamp (control), blue light-emitting diodes (LED) light, or red LED light. After 4 weeks, growth, stomatal ultrastructure, total phenols and flavonoids, activities of antioxidant enzymes, and protein expressions were determined. Interestingly, blue or red LED treatment increased the shoot length, shoot diameter, root length, and biomass on comparison with the control. In addition, the LED treatments enhanced the contents of phytochemicals in the extracts. The red LED treatment significantly elicited the accumulation of flavonoids in comparison with the control. In accordance with the secondary metabolites, the LED treatments modulated the activities of antioxidant enzymes. Moreover, the proteomic insights using two-dimensional gel electrophoresis system revealed the proteins involved in transcription and translation, carbohydrate mechanism, post-translational modification, and stress responses. Taken together, the incorporation of blue or red LED during in vitro propagation of S. kakudensis can be a beneficial way to increase the plant quality and medicinal values of S. kakudensis.

Enhanced Somatic Embryo Induction of a Tree Peony, Paeonia ostii 'Fengdan', by a Combination of 6-benzylaminopurine (BA) and 1-naphthylacetic Acid (NAA)

Somatic embryogenesis is a preferred method for vegetative propagation due to its high propagation efficiency. In this study, zygotic embryos, cotyledons, and hypocotyls of Paeonia ostii ‘Fengdan’ were used as the explant to induce somatic embryogenesis. The results showed that a combination of 0.5 mg·L⁻¹ thidiazuron (TDZ) and 0.5 mg·L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) was effective in inducing somatic embryos from the zygotic embryo and cotyledon explants. Hypocotyls only formed somatic embryos on Murashige and Skoog (MS) medium supplemented with both 0.5 mg·L⁻¹ TDZ and 0.5 mg·L⁻¹ 1-naphthylacetic acid (NAA). Moreover, the compact callus was effectively produced from zygotic embryo, cotyledon, and hypocotyl explants in medium supplemented with a combination of 3.0 mg·L⁻¹ 6-benzylaminopurine (BA) and 1.0 mg·L⁻¹ NAA, and then converted into somatic embryos in the same medium, and the ratio of the explants with embryo induction and number of embryos induced per explant were much higher than those induced by 0.5 mg·L⁻¹ TDZ and either 0.5 mg·L⁻¹ 2,4-D or 0.5 mg·L⁻¹ NAA. The MS medium was better than the woody plant medium (WPM) for inducing somatic embryos from zygotic embryo and hypocotyl explants, whereas the WPM was better than the MS medium for somatic embryogenesis induction from cotyledon explants. All of the somatic embryos developed well into mature embryos on their respective media supplemented with both 3.0 mg·L⁻¹ BA and 1.0 mg·L⁻¹ NAA. Overall, the protocols for indirect somatic embryogenesis from zygotic embryo, cotyledon, and hypocotyl of P. ostii ‘Fengdan’ were successfully established, which can greatly facilitate their propagation and breeding processes.

Night Temperature Affects the Growth, Metabolism, and Photosynthetic Gene Expression in Astragalus membranaceus and Codonopsis lanceolata Plug Seedlings

Astragalus membranaceus and Codonopsis lanceolata are two important medical herbs used in traditional Oriental medicine for preventing cancer, obesity, and inflammation. Night temperature is an important factor that influences the plug seedling quality. However, little research has focused on how the night temperature affects the growth and development of plug seedlings of these two medicinal species. In this study, uniform plug seedlings were cultivated in three environmentally controlled chambers for four weeks under three sets of day/night temperatures (25/10 °C, 25/15 °C, or 25/20 °C), the same relative humidity (75%), photoperiod (12 h), and light intensity (150 μmol·m-2·s-1 PPFD) provided by white LEDs. The results showed that night temperature had a marked influence on the growth and development of both species. The night temperature of 15 °C notably enhanced the quality of plug seedlings evidenced by the increased shoot, root, and leaf dry weights, stem diameter, and Dickson's quality index. Moreover, a night temperature of 15 °C also stimulated and increased contents of primary and secondary metabolites, including soluble sugar, starch, total phenols and flavonoids. Furthermore, the 15 °C night temperature increased the chlorophyll content and stomatal conductance and decreased the hydrogen peroxide content. Analysis of the gene expression showed that granule-bound starch synthase (GBSS), ribulose bisphosphate carboxylase large chain (RBCL), and ferredoxin (FDX) were up-regulated when the night temperature was 15 °C. Taken together, the results suggested that 15 °C is the optimal night temperature for the growth and development of plug seedlings of A. membranaceus and C. lanceolata.

Particulate matter in the cultivation area may contaminate leafy vegetables with heavy metals above safe levels in Korea

Among air pollutants, particulate matter (PM) has been identified as a major cause of environmental pollutants due to the advancement of industrial development and the generation of smaller particles. Particulate matter, in particular, is defined only by the size of particles and thus is not enough to study its composition yet. However, edible crops grown in contaminated atmospheres can be contaminated with heavy metals contained in particulate matter in the atmosphere, which can seriously damage food safety. In this study, we investigated the influence of the accumulation of particulate matter on leafy vegetables cultivated at areas with different levels of PM in atmosphere. Four districts of Gyeongsangnam-do were chosen to conduct this experiment: outdoor spaces of three respectively located in industrial, near-highway, and rural areas were considered, and research plant growth chambers at Gyeongsang National University were used as the control. After 3 weeks of cultivation in those conditions, the results showed that Pb in milligrams per kilogram of fresh weight (FW) was 0.383 in Chrysanthemum coronarium and 0.427 in Spinacia oleracea that were grown near the highway, which exceeded the 0.3 mg kg^-1 FW standard set by the Republic of Korea, EU, and CODEX. However, when those vegetables were sufficiently washed with tap water, it was confirmed that the heavy metal content fell into the safety standard range.

Silicon Affects Root Development, Tissue Mineral Content, and Expression of Silicon Transporter Genes in Poinsettia (Euphorbia pulcherrima Willd.) Cultivars

The effects of silicon (Si) on root development, mineral content, and expression of Si transporter genes in Euphorbia pulcherrima Willd. ‘Flame’, ‘Mable Bell’, ‘Green Star’, ‘Pink Bell’, and ‘Peach Bowl’ cultivars were investigated in this study. Stem cuttings in a propagation bench were drenched regularly with a solution containing either 0 (control) or 50 ppm of silicon (Si treatment) from potassium silicate (K₂SiO₃), with a 25 °C mean air temperature and 80% relative humidity (RH) under 70% shading. The results showed that the ‘Flame’ treated with Si had a significantly higher survival ratio as compared with that of the control (P ≤ 0.05) and that the Si treatment improved number of roots, length of longest root, fresh root weight, and dry root weight in all cultivars except ‘Mable Bell’. Supplementary Si increased the content of magnesium (Mg) and decreased the content of boron (B) and zinc (Zn) in the roots. The content of sulfur (S) in the shoots was increased by supplementary Si. The relative expression of Lsi1 and Lsi2 was higher in ‘Peach Bowl’, while it was lower in ‘Mable Bell’ and ‘Green Star’, which may be caused by the differing accumulation of Si in the shoot. Overall, supplementary Si had beneficial effects during cutting propagation of poinsettia cultivars, although these effects were cultivar-dependent.

Light elicited growth, antioxidant enzymes activities and production of medicinal compounds in callus culture of Cnidium officinale Makino

Cnidium officinale Makino is an important medicinal plant of oriental clinics and is considered as the main source of phthalides, polyphenols, and flavonoids. However, there is no available report regarding the effect of different light colors on the secondary metabolites composition of C. officinale. In this study different light (dark, white, blue, red and red: blue) conditions were arranged to raise callus on MS medium containing 0.5 mg·L^-1 of each 2,4-D and BAP. Callus grown in dark condition showed maximum (2.0 g) fresh weight with lower total phenolic and flavonoids contents. Also, in dark condition callus faced higher catalase (CAT) and guaiacol peroxidase (GPX) activities to avoid free radicals. Mix (red: blue) light condition favored the synthesis of phenolics and flavonoids in callus at the cost of higher ascorbate peroxidase (APX) and superoxide dismutase (SOD) enzymes expression. However, DPPH free radical scavenging activity was less variable among the samples from the different light conditions. Interestingly, the HPLC profile showed higher (28.3 μg·g^-1 DW) phthalide accumulation in dark grown-cultures. Compared to other light conditions, 3-butyledinephthalide accumulation was higher (0.43 μg·g^-1 DW) in white light-grown callus. These findings suggest that light conditions play an important role in the regulation of in vitro callus growth and synthesis of important medicinal compounds of C. officinale.

Enhanced growth and cardenolides production in Digitalis purpurea under the influence of different LED exposures in the plant factory

In this report, we have investigated the influence of different light qualities on Digitalis purpurea under a controlled environment. For this purpose, red (R), blue (B), fluorescent lamp (FL, control), along with combined red and blue (R:B) LEDs were used. Interestingly, the plant growth parameters such as number of leaf, longest root, width of leaf, width of stomata, width of trichome, leaf area, leaf or root fresh weight (FW), weight (DW) as well as length of trichome were maximum under R:B (8:2), and significantly larger than control plants. The stomatal conductance or anthocyanin was maximum under B LED than those under FL, however the photosynthesis rate was greater under FL. RuBisCO activity was maximum under R:B (1:1) LEDs while the quantity of the UV absorbing substances was highest under R LED than under FL. The maximum amount of cardenolides were obtained from leaf tissue under R:B (2:8) LED than those under FL. The R:B LEDs light was suitable for Digitalis plant growth, development, micro- and macro-elements, as well as cardenolides accumulation in the plant factory system. The adaptation of the growth strategy developed in this study would be useful for the production of optimized secondary metabolites in Digitalis spp.

Supplementary Light Source Affects the Growth and Development of Codonopsis lanceolata Seedlings

Codonopsis lanceolata is widely used in traditional medicine and diets. However, there is no optimal protocol for the commercial production of C. lanceolata seedlings. This study was carried out to find the optimum supplementary light source for the production of C. lanceolata seedlings. Seedlings were grown for four weeks in a glasshouse with an average daily light intensity of 490 μmol·m⁻²·s⁻¹ photosynthetic photon flux density (PPFD) coming from the sun and a 16-h daily supplementary lighting at 120 μmol·m⁻²·s⁻¹ PPFD from either high-pressure sodium (HPS), metal halide (MH), far-red (FR), white LED (LED-w), or mixed (white: red: blue = 1:2:1) LEDs (LED-mix). The results showed that the greatest total biomass, stem diameter, ratio of shoot weight to shoot length, root biomass, and ratio of root weight to shoot weight were found in seedlings grown under supplementary LED-mix. Meanwhile, the stomatal properties and soluble sugar contents were improved for seedlings in LED-mix. The contents of starch, total phenols, and flavonoids were the greatest for seedlings in LED-w and LED-mix. The expression of photosynthetic proteins and genes in seedlings was also enhanced by LED-mix. Overall, these results suggest that LED-mix is advantageous to the photosynthetic potential and the accumulation of biomass, carbohydrates and secondary metabolites in C. lanceolata.

Data on recurrent somatic embryogenesis and in vitro micropropagation of Cnidium officinale Makino

Cnidium officinale Makino, a perennial herb of the family Umbelliferae, is a well-known medicinal plant in oriental medicine with antidiabetic, tumor metastatic, antiplatelet, antimicrobial and insecticidal properties. Hence, C. officinale does not produce seed the plant tissue culture is the viable alternative for its propagation. Node explant from in vitro grown C. officinale Makino was cultured on MS medium supplemented with plant growth regulators (PGRs) like 2,4-Dichlorophenoxyacetic acid (2,4-D) or/and 6-Benzylaminopurine (BA). It was aimed to investigate the optimal concentration and combination of 2,4-D and BA for somatic embryogenesis in node explant of C. officinale Makino. The embryogenic callus was induced on node explant after four weeks in MS medium containing 1.5 mg L^-1 2,4-D and 0.5 mg L^-1 BA. The translucent white, embryogenic callus was subcultured on the respective medium and individual well-structured somatic embryos were observed. Heart and cotyledon stage embryos were pictured under a stereomicroscope. The individual somatic embryos (SE) were transferred to MS medium without PGRs (MS0) and 100% germination was observed. Repeated subculturing of the embryogenic callus for five months resulted in recurrent somatic embryogenesis but with a gradual decline in number.

Silicon (Si): Review and future prospects on the action mechanisms in alleviating biotic and abiotic stresses in plants

In the era present, due to increasing incidences of a large number of different biotic and abiotic stresses all over the world, the growth of plants (principal crops) may be restrained by these stresses. In addition to beneficial microorganisms, use of silicon (Si)-fertilizer is known as an ecologically compatible and environmentally friendly technique to stimulate plant growth, alleviate various biotic and abiotic stresses in plants, and enhance the plant resistance to multiple stresses, because Si is not harmful, corrosive, and polluting to plants when presents in excess. Here, we reviewed the action mechanisms by which Si alleviates abiotic and biotic stresses in plants. The use of Si (mostly as industrial slags and rice straw) is predicted to become a sustainable strategy and an emerging trend in agriculture to enhance crop growth and alleviate abiotic and biotic stresses in the not too distant future. In this review article, the future research needs on the use of Si under the conditions of abiotic and biotic stresses are also highlighted.

Proteomic Analysis Reveals the Dynamic Role of Silicon in Alleviation of Hyperhydricity in Carnation Grown In Vitro

The present study depicted the role of silicon in limiting the hyperhydricity in shoot cultures of carnation through proteomic analysis. Four-week-old healthy shoot cultures of carnation "Purple Beauty" were sub-cultured on Murashige and Skoog medium followed with four treatments, viz. control (-Si/-Hyperhydricity), hyperhydric with no silicon treatment (-Si/+Hyperhydricity), hyperhydric with silicon treatment (+Si/+Hyperhydricity), and only silicon treated with no hyperhydricity (+Si/-Hyperhydricity). Comparing to control morphological features of hyperhydric carnations showed significantly fragile, bushy and lustrous leaf nature, while Si supply restored these effects. Proteomic investigation revealed that approximately seventy protein spots were differentially expressed under Si and/or hyperhydric treatments and were either up- or downregulated in abundance depending on their functions. Most of the identified protein spots were related to stress responses, photosynthesis, and signal transduction. Proteomic results were further confirmed through immunoblots by selecting specific proteins such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), PsaA, and PsbA. Moreover, protein-protein interaction was also performed on differentially expressed protein spots using specific bioinformatic tools. In addition, stress markers were analyzed by histochemical localization of hydrogen peroxide (H₂O₂) and singlet oxygen (O₂1-). In addition, the ultrastructure of chloroplasts in hyperhydric leaves significantly resulted in inefficiency of thylakoid lamella with the loss of grana but were recovered in silicon supplemented leaves. The proteomic study together with physiological analysis indicated that Si has a substantial role in upholding the hyperhydricity in in vitro grown carnation shoot cultures.

Leaf Physiological and Proteomic Analysis to Elucidate Silicon Induced Adaptive Response under Salt Stress in Rosa hybrida 'Rock Fire'

Beneficial effects of silicon (Si) on growth and development have been witnessed in several plants. Nevertheless, studies on roses are merely reported. Therefore, the present investigation was carried out to illustrate the impact of Si on photosynthesis, antioxidant defense and leaf proteome of rose under salinity stress. In vitro-grown, acclimatized Rosa hybrida 'Rock Fire' were hydroponically treated with four treatments, such as control, Si (1.8 mM), NaCl (50 mM), and Si+NaCl. After 15 days, the consequences of salinity stress and the response of Si addition were analyzed. Scorching of leaf edges and stomatal damages occurred due to salt stress was ameliorated under Si supplementation. Similarly, reduction of gas exchange, photosynthetic pigments, higher lipid peroxidation rate, and accumulation of reactive oxygen species under salinity stress were mitigated in Si treatment. Lesser oxidative stress observed was correlated with the enhanced activity and expression of antioxidant enzymes, such as superoxide dismutase, catalase, and ascorbate peroxidase in Si+NaCl treatment. Importantly, sodium transportation was synergistically restricted with the stimulated counter-uptake of potassium in Si+NaCl treatment. Furthermore, two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) results showed that out of 40 identified proteins, on comparison with control 34 proteins were down-accumulated and six proteins were up-accumulated due to salinity stress. Meanwhile, addition of Si with NaCl treatment enhanced the abundance of 30 proteins and downregulated five proteins. Differentially-expressed proteins were functionally classified into six groups, such as photosynthesis (22%), carbohydrate/energy metabolism (20%), transcription/translation (20%), stress/redox homeostasis (12%), ion binding (13%), and ubiquitination (8%). Hence, the findings reported in this work could facilitate a deeper understanding on potential mechanism(s) adapted by rose due to the exogenous Si supplementation during the salinity stress.

Physiological and Proteomic Investigations to Study the Response of Tomato Graft Unions under Temperature Stress

BACKGROUND

Grafting is an established practice for asexual propagation in horticultural and agricultural crops. The study on graft unions has become of interest for horticulturists using proteomic and genomic techniques to observe transfer of genetic material and signal transduction pathways from root to shoot and shoot to root. Another reason to study the graft unions was potentially to observe resistance against abiotic stresses. Using physiological and proteomic analyses, we investigated graft unions (rootstock and scions) of tomato genotypes exposed to standard-normal (23/23 and 25/18°C day/night) and high-low temperatures (30/15°C day/night).

RESULTS

Graft unions had varied responses to the diverse temperatures. High-low temperature, but not standard-normal temperature, induced the production of reactive oxygen species (ROS) in the form of H2O2 and O2-1 in rootstock and scions. However, the expression of many cell protection molecules was also induced, including antioxidant enzymes and their immunoblots, which also show an increase in their activities such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). The graft interfaces thus actively defend against stress by modifying their physiological and proteomic responses to establish a new cellular homeostasis. As a result, many proteins for cellular defense were regulated in graft unions under diverse temperature, in addition to the regulation of photosynthetic proteins, ion binding/transport proteins, and protein synthesis. Moreover, biomass, hardness, and vascular transport activity were evaluated to investigate the basic connectivity between rootstock and scions.

CONCLUSIONS

Our study provides physiological evidence of the grafted plants' response to diverse temperature. Most notably, our study provides novel insight into the mechanisms used to adapt the diverse temperature in graft unions (rootstock/scion).

Genotypic Variation under Fe Deficiency Results in Rapid Changes in Protein Expressions and Genes Involved in Fe Metabolism and Antioxidant Mechanisms in Tomato Seedlings (Solanum lycopersicum L.)

To investigate Fe deficiency tolerance in tomato cultivars, quantification of proteins and genes involved in Fe metabolism and antioxidant mechanisms were performed in “Roggusanmaru” and “Super Doterang”. Fe deficiency (Moderate, low and –Fe) significantly decreased the biomass, total, and apoplastic Fe concentration of “Roggusanmaru”, while a slight variation was observed in “Super Doterang” cultivar. The quantity of important photosynthetic pigments such as total chlorophyll and carotenoid contents significantly decreased in “Roggusanmaru” than “Super Doterang” cultivar. The total protein profile in leaves and roots determines that “Super Doterang” exhibited an optimal tolerance to Fe deficiency compared to “Roggusanmaru” cultivar. A reduction in expression of PSI (photosystem I), PSII (photosystem II) super-complexes and related thylakoid protein contents were detected in “Roggusanmaru” than “Super Doterang” cultivar. Moreover, the relative gene expression of SlPSI and SlPSII were well maintained in “Super Doterang” than “Roggusanmaru” cultivar. The relative expression of genes involved in Fe-transport (SlIRT1 and SlIRT2) and Fe(III) chelates reductase oxidase (SlFRO1) were relatively reduced in “Roggusanmaru”, while increased in “Super Doterang” cultivar under Fe deficient conditions. The H⁺-ATPase relative gene expression (SlAHA1) in roots were maintained in “Super Doterang” compared to “Roggusanmaru”. Furthermore, the gene expressions involved in antioxidant defense mechanisms (SlSOD, SlAPX and SlCAT) in leaves and roots showed that these genes were highly increased in “Super Doterang”, whereas decreased in “Roggusanmaru” cultivar under Fe deficiency. The present study suggested that “Super Doterang” is better tomato cultivar than “Roggusanmaru” for calcareous soils.

Proteomic Analysis Provides New Insights in Phosphorus Homeostasis Subjected to Pi (Inorganic Phosphate) Starvation in Tomato Plants (Solanum lycopersicum L.)

Phosphorus is a major nutrient acquired by plants via high-affinity inorganic phosphate (Pi) transporters. To determine the adaptation and homeostasis strategy to Pi starvation, we compared the proteome analysis of tomato leaves that were treated with and without Pi (as KH2PO4) for 10 days. Among 600 reproducible proteins on 2-DE gels 46 of them were differentially expressed. These proteins were involved in major metabolic pathways, including photosynthesis, transcriptional/translational regulations, carbohydrate/energy metabolism, protein synthesis, defense response, and other secondary metabolism. The results also showed that the reduction in photosynthetic pigments lowered P content under -Pi treatments. Furthermore, high-affinity Pi transporters (lePT1 and lePT2) expressed in higher amounts under -Pi treatments. Also, the accumulation of Pi transporters was observed highly in the epidermis and palisade parenchyma under +Pi treatments compared to -Pi treatments. Our data suggested that tomato plants developed reactive oxygen species (ROS) scavenging mechanisms to cope with low Pi content, including the up-regulation of proteins mostly involved in important metabolic pathways. Moreover, Pi-starved tomato plants increased their internal Pi utilization efficiency by increasing the Pi transporter genes and their rational localization. These results thus provide imperative information about how tomato plants respond to Pi starvation and its homeostasis.

Morphogenesis, Flowering, and Gene Expression of Dendranthema grandiflorum in Response to Shift in Light Quality of Night Interruption

The impact of shifts in the spectral quality of light on morphogenesis, flowering, and photoperiodic gene expression during exposure to light quality of night interruption (NI) was investigated in Dendranthema grandiflorum. The circadian rhythms of plants grown in a closed walk-in growth chamber were interrupted at night for a total of 4 h, using light-emitting diodes with an intensity of 10 μmol·m⁻²·s⁻¹ PPF. The light quality of the NI was shifted from one wavelength to another after the first 2 h. Light treatments consisting of all possible pairings of blue (B), red (R), far-red (Fr), and white (W) light were tested. Plants in the NI treatment groups exposed to Fr light grew larger than plants in other treatment groups. Of plants in NI treatment groups, those in the NI-WB treatment grew the least. In addition, the impact of shifts in the light quality of NI on leaf expansion was greater in treatment groups exposed to a combination of either B and R or R and W light, regardless of their order of supply. Flowering was observed in the NI-RB, NI-FrR, NI-BFr, NI-FrB, NI-WB, NI-FrW, NI-WFr, NI-WR, and SD (short-day) treatments, and was especially promoted in the NI-BFr and NI-FrB treatments. In a combined shift treatment of B and R or B and W light, the NI concluded with B light (NI-RB and NI-WB) treatment induced flowering. The transcriptional factors phyA, cry1 and FTL (FLOWERING LOCUS T) were positively affected, while phyB and AFT were negatively affected. In conclusion, morphogenesis, flowering, and transcriptional factors were all significantly affected either positively or negatively by shifts in the light quality of NI. The light quality of the first 2 h of NI affected neither morphogenesis nor flowering, while the light quality of the last 2 h of NI significantly affected both morphogenesis and flowering.

Proteomic study related to vascular connections in watermelon scions grafted onto bottle-gourd rootstock under different light intensities

Although grafting is broadly used in the production of crops, no information is available about the proteins involved in vascular connections between rootstock and scion. Similarly, proteome changes under the light intensities widely used for grafted seedlings are of practical use. The objective of this study was to determine the proteome of vascular connections using watermelon (Citrullus vulgaris Schrad.) ‘Sambok Honey’ and ‘Speed’ as the scion and bottle gourd (Lagenaria siceraria Stanld.) ‘RS Dongjanggun’ as the rootstock grown under different light intensities (25, 50, 75 and 100 μmol m⁻² s⁻¹). Our proteomic analysis revealed 24 and 27 differentially expressed proteins in ‘Sambok Honey’ and ‘Speed’, respectively, under different light intensities. The identified proteins were largely involved in ion binding, amino acid metabolism, transcriptional regulation and defense response. The enhancement of ion-binding, transcriptional regulation, amino acid metabolism, and defense response proteins suggests a strengthening of the connection between the rootstock and scion under high light intensity. Indeed, the accumulation of key enzymes in the biological processes described above appears to play an important role in the vascular connections of grafted seedlings. Moreover, it appears that 100 μmol m⁻² s⁻¹ results in better protein expression responses in grafted seedlings.

Physiological and proteomic analysis in chloroplasts of Solanum lycopersicum L. under silicon efficiency and salinity stress

Tomato plants often grow in saline environments in Mediterranean countries where salt accumulation in the soil is a major abiotic stress that limits its productivity. However, silicon (Si) supplementation has been reported to improve tolerance against several forms of abiotic stress. The primary aim of our study was to investigate, using comparative physiological and proteomic approaches, salinity stress in chloroplasts of tomato under silicon supplementation. Tomato seedlings (Solanum lycopersicum L.) were grown in nutrient media in the presence or absence of NaCl and supplemented with silicon for 5 days. Salinity stress caused oxidative damage, followed by a decrease in silicon concentrations in the leaves of the tomato plants. However, supplementation with silicon had an overall protective effect against this stress. The major physiological parameters measured in our studies including total chlorophyll and carotenoid content were largely decreased under salinity stress, but were recovered in the presence of silicon. Insufficient levels of net-photosynthesis, transpiration and stomatal conductance were also largely improved by silicon supplementation. Proteomics analysis of chloroplasts analyzed by 2D-BN-PAGE (second-dimensional blue native polyacrylamide-gel electrophoresis) revealed a high sensitivity of multiprotein complex proteins (MCPs) such as photosystems I (PSI) and II (PSII) to the presence of saline. A significant reduction in cytochrome b6/f and the ATP-synthase complex was also alleviated by silicon during salinity stress, while the complex forms of light harvesting complex trimers and monomers (LHCs) were rapidly up-regulated. Our results suggest that silicon plays an important role in moderating damage to chloroplasts and their metabolism in saline environments. We therefore hypothesize that tomato plants have a greater capacity for tolerating saline stress through the improvement of photosynthetic metabolism and chloroplast proteome expression after silicon supplementation.

Transcriptional and physiological changes in relation to Fe uptake under conditions of Fe-deficiency and Cd-toxicity in roots of Vigna radiata L

We investigated transcriptional and physiological changes in relation to Fe transport and uptake under various conditions of iron (Fe)-deficiency and cadmium (Cd) toxicity. Responses to four such Fe/Cd conditions were evaluated, revealing that oxidative stress was generated in the presence of Cd, followed by a decrease in Fe and an increase in Cd concentrations in green gram (Vigna radiata) material, whereas supplementation with Fe had a protective effect against Cd toxicity. The involvement of enzymes in Fe-uptake for the formation of root-nodules was largely reduced in the presence of Cd toxicity, a condition recovered by Fe-supplementation. Insufficient ferric chelate reducing activity in Fe-deprived roots in the presence of Cd was also largely improved by Fe supplementation. The expression of Fe(2+) transporters (IRT1, IRT2, and IRT3), Fe(III) chelate reductase (FRO1-FRO8) and phytochelatin synthase (PCS1, PCS2 and PCS3) genes was up regulated for the first 5 days and decreased after 10 days in roots in the presence of Cd toxicity, but was sustained with Fe-supplementation. Additionally, root biomass was fully recovered in plants in the presence of Fe during Cd toxicity. Our results suggest that Fe-status plays a significant role in ameliorating the damage in Fe transport for chelation and its uptake caused by Cd toxicity. This supports the hypothesis that leguminous plants, particularly those that are sensitive to Fe such as green gram, can cope to some extent with Cd toxicity by improving the uptake and transport of Fe.

Effect of cytokinins on in vitro multiplication of Sophora tonkinensis

OBJECTIVE

To determine the effects of different cytokinins at various concentrations on in vitro shoot multiplication of an important medicinal plant.

METHODS

Nodal explants (1.5-2.0 cm) of Sophora tonkinensis were used. Multiple shoots were induced from nodal explants cultured on the Murashige and Skoog (MS) medium supplemented with 0.0, 0.5, 1.0, 2.0, 4.0, 8.0, or 16.0 µmol 2-isopentyladenine (2iP), N6 benzyladenine, kinetin or thiadiazuron.

RESULTS

Among the four investigated cytokinins, 2iP showed the best response for shoot multiplication. Maximum shoot induction (75%) was achieved on the MS medium supplemented with 2.0 µmol 2iP, with a mean number of 5.0 shoots per explant. In comparison to other cytokinins tried, 2iP showed the highest shoot elongation with a mean shoot length of 4.8 cm. Root initiation was observed within 15 d within the transfer of shoots onto the MS basal medium, and the rooting percentage was 100% with a mean number of 5.4 roots per shoot and root length of 6.2 cm over a period of 4 weeks. The healthy plants, hardened and transferred to a greenhouse for proper acclimatization, exhibited 100% survival.

CONCLUSIONS

It can be summarized that 2iP is the optimal plant growth regulator for Sophora multiplication.

Structural, vibrational (FT-IR and FT-Raman) and UV-Vis spectral analysis of 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea by DFT method

The Fourier Transform Infrared (FT-IR) and FT-Raman spectra of 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea (TDZ) have been recorded and analyzed. The molecular structure and vibrational spectra (harmonic and anharmonic) of TDZ were calculated by the Density Functional Theory (DFT) method using the B3LYP function with 6-31G(d,p) as the basis set. A detailed interpretation of the Infrared and Raman spectra of TDZ was reported based on Potential Energy Distribution (PED). The first order hyperpolarizability (β(0)) of this novel molecular system and related properties (β, α(0) and Δα) were calculated using HF/6-31G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions and charge delocalization have been analyzed using Natural Bond Orbital analysis. The results show that charge in electron density in the σ(∗) and π(∗) antibonding orbitals and second order delocalization energies E(2) confirm the occurrence of Intramolecular Charge Transfer (ICT) within the molecule. UV-Vis spectrum of the title molecule was recorded and the electronic properties such as HOMO and LUMO energies were determined by Time-Dependent Density Functional Theory approach.

Pn-AMPs, the hevein-like proteins from Pharbitis nil confers disease resistance against phytopathogenic fungi in tomato, Lycopersicum esculentum

The antifungal activity of hevein-like proteins has been associated with their chitin-binding activities. Pn-AMP1 and Pn-AMP2, two hevein homologues from Pharbitis nil, show in vitro antifungal activities against both chitin and non-chitin containing fungi. Purified Pn-AMPs retained antifungal activities only under non-reducing conditions. When Pn-AMP2 cDNA was constitutively expressed in tomato (Lycopersicon esculentum) plants under the control of CaMV35S promoter, the transgenic plants showed enhanced resistance against both the non-chitinous fungus Phytophthora capsici, and the chitin-containing fungus Fusarium oxysporum. Thus, the chitin component in the fungal cell wall is not an absolute requirement for Pn-AMP's antifungal activities. These results when considered together suggest that Pn-AMPs have the potential for developing transgenic plants resistant to a wide range of phytopathogenic fungi.

Loss of pendimethalin in runoff and leaching from turfgrass land under simulated rainfall

A field study was undertaken to investigate runoff and leaching loss of the herbicide pendimethalin in turfgrass land of loamy sand soil. A series of plots constructed in a golf course fairway were surface-applied with pendimethalin SC formulation at the rate of 2. 25 or 4.50 kg a.i./ha and subjected to simulated rainfall at 2.0 cm/day for 10 consecutive days. Runoff losses of pendimethalin were the highest at the first rainfall and then gradually decreased with time. The first runoff event contained pendimethalin in its highest concentration, and in subsequent runoff samples the concentration decreased exponentially. The ranges of pendimethalin concentration were 80.9-18.2 and 177.4-48.6 microgram/L in the standard and double doses, respectively. Total losses by 20 cm of rainfall for 10 days reached 0.81 and 1.22% of the initial deposits at 2.25 and 4.50 kg a. i./ha, respectively. Pendimethalin concentration in the leachate collected at 30-cm soil depth was quite lower than that in the runoff, and the concentration rapidly decreased from 4.3-4.7 to 0. 2-0.4 microgram/L during the 10 days of rainfall treatment. Soil residue analysis at 45 and 90 days after pendimethalin treatment showed that more than 90% of the residue remained at the top 10 cm of soil depth. Low runoff and leaching confirmed that lateral and downward movement of the herbicide should be limited in turf soil. The half-life of pendimethalin under field conditions was 23-30 days and was not affected by application dose and rainfall treatment, but longer persistence was observed under laboratory conditions. Considering low runoff and leaching, as well as relatively short persistence in soil, it is concluded that little environmental carryover of pendimethalin would be expected in turfgrass land.

Starch and the control of kernel number in maize at low water potentials

After reproduction is initiated in plants, subsequent reproductive development is sometimes interrupted, which decreases the final number of seeds and fruits. We subjected maize (Zea mays L.) to low water potentials (psi(w)) that frequently cause this kind of failure. We observed metabolite pools and enzyme activities in the developing ovaries while we manipulated the sugar stream by feeding sucrose (Suc) to the stems. Low psi(w) imposed for 5 d around pollination allowed embryos to form, but abortion occurred and kernel number decreased markedly. The ovary contained starch that nearly disappeared during this abortion. Analyses showed that all of the intermediates in starch synthesis were depleted. However, when labeled Suc was fed to the stems, label arrived at the ovaries. Solute accumulated and caused osmotic adjustment. Suc accumulated, but other intermediates did not, showing that a partial block in starch synthesis occurred at the first step in Suc utilization. This step was mediated by invertase, which had low activity. Because of the block, Suc feeding only partially prevented starch disappearance and abortion. These results indicate that young embryos abort when the sugar stream is interrupted sufficiently to deplete starch during early ovary development, and this abortion results in a loss of mature seeds and fruits. At low psi(w), maintaining the sugar stream partially prevented the abortion, but invertase regulated the synthesis of ovary starch and partially prevented full recovery.