β-Pinene inhibited germination and early growth involves membrane peroxidation

Selective Biotic Stressors' Action on Seed Germination: A Review

In the realm of plant biology and agriculture, seed germination serves as a fundamental process with far-reaching implications for crop production and environmental health. This comprehensive review seeks to unravel the intricate web of interactions between some biotic stressors and seed germination, addressing the pertinent issue of how these stressors influence seed germination. Different chemicals produced by interacting plants (different parts), fungi, bacteria, or insects can either promote or inhibit seed germination. Releasing chemicals that modulate signaling pathways and cellular processes significantly disrupt essential cellular functions. This disruption leads to diverse germination outcomes, introducing additional layers of complexity to this regulatory landscape. The chemicals perturb enzyme activity and membrane integrity, imposing unique challenges on the germination process. Understanding the mechanisms- how allelochemicals, mycotoxins, or bacterial toxins affect seed germination or the modes of action holds promise for more sustainable agricultural practices, enhanced pest control, and improved environmental outcomes. In sum, this review contributes to a fundamental exposition of the pivotal role of biotic stressors in shaping the germination of seeds.

Biological Activities of the Fruit Essential Oil, Fruit, and Root Extracts of Ferula drudeana Korovin, the Putative Anatolian Ecotype of the Silphion Plant

In the present study, preliminary phytochemical investigations were performed on the fruit essential oil and antioxidant-rich methanolic extracts of the fruits and roots of Ferula drudeana, the putative Anatolian ecotype of the Silphion plant, to corroborate its medicinal plant potential and identify its unique characteristics amongst other Ferula species. The essential oil from the fruits of the endemic species Ferula drudeana collected from Aksaray was analyzed by GC and GC/MS. The main components of the oil were determined as shyobunone (44.2%) and 6-epishyobunone (12.6%). The essential oil of the fruits and various solvent extracts of the fruits and roots of F. drudeana were evaluated for their antibacterial and anticandidal activity using microbroth dilution methods. The essential oil of the fruits, methanol, and methylene chloride extracts of the fruits and roots showed weak to moderate inhibitory activity against all tested microorganisms with MIC values of 78-2000 µg/mL. However, the petroleum ether extract of the roots showed remarkable inhibitory activity against Candida krusei and Candida utilis with MIC values of 19.5 and 9.75 µg/mL, respectively. Furthermore, all the samples were tested for their antioxidant activities using DPPH^• TLC spot testing, online HPLC-ABTS screening, and DPPH/ABTS radical scavenging activity assessment assays. Methanolic extracts of the fruits and roots showed strong antioxidant activity in both systems.

Allelopathic Effects of Amomum villosum Lour. Volatiles from Different Organs on Selected Plant Species and Soil Microbiota

Amomum villosum Lour. is a perennial herb of the Zingiberaceae family, which is widely distributed in Xishuangbanna, Yunnan Province in Southwest China. Large amounts of volatile components contained in this plant enter the surrounding atmosphere and soil through volatilization, foliar leaching, root exudation, and residue decomposition. However, the ecological role of these compounds is currently unclear. The aim of this study was to compare the differences in the composition of volatile oils from stems, leaves, and young fruits of A. villosum, identify chemicals that had allelopathic effects, and explore the effects of the oil on the diversity and composition of soil microbiomes. Volatile oils were obtained by steam distillation and characterized by gas chromatography−mass spectrometry, and then were tested for allelopathic activity using seedlings of Lactuca sativa L. and Lolium perenne L. as test species. The results showed that the oils from stems and leaves were rich in monoterpene hydrocarbons, unlike the oxygenated monoterpenes which dominated oils from young fruits. Leaves > stems > young fruits: this was the order of the allelopathic effects of volatile oils from various A. villosum organs. Among the four main chemical components in the oils, only α-pinene, which is abundant in leaves, had a stronger allelopathic action than the crude oils, implying that it might be a potential allelochemical. Experiments on soil microorganisms indicated that 3.0 mg/mL oil had the greatest effect on the structure of the soil fungal community. It can be concluded that A. villosum is capable of releasing allelochemicals which affect the growth of other plant species and the diversity and community structure of soil microorganisms.

Allelopathy and Allelochemicals of Solidago canadensis L. and S. altissima L. for Their Naturalization

Solidago canadensis L. and Solidago altissima L. are native to North America and have naturalized many other continents including Europa and Asia. Their species is an aggressive colonizer and forms thick monospecific stands. The evidence of the allelopathy for S. canadensis and S. altissima has accumulated in the literature since the late 20th century. The root exudates, extracts, essential oil and rhizosphere soil of S. canadensis suppressed the germination, growth and the arbuscular mycorrhizal colonization of several plants, including native plant species. Allelochemicals such as fatty acids, terpenes, flavonoids, polyphenols and their related compounds were identified in the extracts and essential oil of S. canadensis. The concentrations of total phenolics, total flavonoids and total saponins in the rhizosphere soil of S. canadensis obtained from the invasive ranges were greater than those from the native ranges. Allelochemicals such as terpenes, flavonoids, polyacetylene and phenols were also identified in the extracts, essential oil and the rhizosphere soil in S. altissima. Among the identified allelochemicals of S. altissima, the cis-dehydromatricaria ester may be involved in the allelopathy considering its growth inhibitory activity and its concentration in the rhizosphere soil. Therefore, the allelopathy of S. canadensis and S. altissima may support their invasiveness, naturalization and formation of thick monospecific stands. This is the first review article focusing on the allelopathy of both of S. canadensis and S. altissima.

Pesticidal Activity and Mode of Action of Monoterpenes

Synthetic pesticides are often associated with issues such as pest resistance, persistent residue, nontarget toxicity, and environmental issues. Therefore, the research and development of novel, safe, and effective pesticides has become a focus in pesticide discovery. Monoterpenes are secondary plant metabolites that commonly have multiple action targets and have been used in aromatherapy, alternative medicine, and food industries. Some are highly potent and stereoselective. They can potentially be botanical pesticides and serve as lead candidates for the design and synthesis of new monoterpenoid pesticides for agricultural applications. This article reviews publications and patents found in SciFinder Scholar between 2000 and May 2021 on monoterpenes and mainly focuses on pesticidal activities of frequently studied monoterpenes and their modes of action. The presented information and our views are hopefully useful for the development of monoterpenes as biopesticides and monoterpenoid pesticides.

Synthesis, Herbicidal Activity and Toxicity Evaluation of Secondary Ammonium Salts from Turpentine Oil for Sustainable Weed Control

Three series of secondary ammonium chloride from turpentine were synthesized and evaluated as botanical herbicides. The preemergence herbicidal activities against ryegrass (Loliun multiflorum) and barnyard grass (Echinochloa crus-galli) were investigated using water as the only solvent. Their toxicity was evaluated by cytotoxicity assays. Preliminary results demonstrated that the herbicidal performance of the prepared salts was similar or much higher than that of corresponding secondary amines and even commercial herbicide glyphosate. Promisingly, compound 14e containing a cyclohexyl-substituted p-menthene skeleton with an IC₅₀ value of 0.0014 mM against root growth of ryegrass showed 39-fold higher herbicidal activity than glyphosate. Besides, this compound was found to be nontoxic to human and animal cells, indicating the potential application as a water-soluble herbicide for ryegrass control.

The Effects of β-Pinene, a Pine Needle Oil Monoterpene, on Adenovirus Type 3

The mechanisms of the inhibitory action of β-pinene, a pine needle oil monoterpene, on human adenovirus type 3 were studied using cytopathic inhibition test, MTT test, atomic force and laser confocal microscopy. β-Pinene inhibited the viruses stronger that the reference antiviral medication ribavirin (p<0.05). Inhibition of viral cytopathic effect (CPE) increased with increasing the concentration of β-pinene, which attested to direct elimination of adenovirus type 3. During viral reproduction phase, β-pinene significantly inhibited proliferation of adenovirus type 3. Typical signs of adenoviral CPE as cell swelling and rounding were less pronounced in comparison with the control (ribavirin treatment). In addition, elevation of β-pinene concentration significantly increased the cell survival rate (p<0.05). Laser confocal microscopy showed that fluorescence intensity in the β-pinene group was significantly lower than in the control group (p<0.01), which was consistent with the results of MTT test, thereby providing additional arguments that β-pinene affects the virus during the absorption phase. Thus, β-pinene directly inactivates adenovirus type 3 and impedes its invasion into the cells, but produces no protective effects on cells. Understanding the mode of action of such monoterpenes as β-pinene is of great importance for the development of new antiviral drugs.

The pinene scaffold: its occurrence, chemistry, synthetic utility, and pharmacological importance

This review provides insight into the utility of pinene in the synthetic building block and as reagent in asymmetric synthesis.

β-Pinene alleviates arsenic (As)-induced oxidative stress by modulating enzymatic antioxidant activities in roots of Oryza sativa

Rice (Oryza sativa L.) is a highly consumed staple crop worldwide, but abiotic/heavy metal stresses acting on the plant cause reduction in yield and quality, thereby impacting global food security. In the present study, we examined the effect of β-pinene against Arsenic (As)-induced oxidative damage vis-à-vis regulation of activities of enzymatic antioxidants in roots of O. sativa. Effect of As (50 μM), β-pinene (10 μM; β-10) and As + β-10 treatments on root length, shoot length, As accumulation, lipid peroxidation (as malondialdehyde [MDA] content), hydrogen peroxide (H₂O₂) accumulation, and activities of lipoxygenase (LOX) and enzymatic antioxidants such as ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT) was determined. Exposure of As caused a decline in root and shoot length, and enhancement in As accumulation, lipid peroxidation, and activities of enzymatic antioxidants. However, supplementation of β-10 (i.e., As + β-10 treatments) led to an increase in root and shoot length. Treatment with As + β-10 resulted in a decline in As accumulation, H₂O₂ content, and MDA content; however, the effect on LOX activity was non-significant, as compared to control. Similarly, with As + β-10 treatment a reduction in the activities of APX, GPX, GR, SOD, and CAT was observed as compared with As-alone treatment. Pearson's correlation matrix exhibited strong negative correlation between reactive oxygen species (ROS) and root/shoot length, whereas a strong positive correlation was observed between antioxidant enzymes and ROS. The present study demonstrated that β-pinene significantly ameliorates As-induced oxidative stress and provides tolerance to O. sativa against As-induced toxicity, and thus offer an option of As-mitigation using environment friendly natural plant products. However, to gain insights into the function of β-pinene in modulating As-induced oxidative damage in plants, further field investigations and exploration of its mechanism of action are needed.

Amelioration potential of β-pinene on Cr(VI)-induced toxicity on morphology, physiology and ultrastructure of maize

Heavy metals' amassment in the soil environment is a threat to crop and agricultural sustainability and consequentially the global food security. For achieving enhancement of crop productivity in parallel to reducing chromium (Cr) load onto food chain demands continuous investigation and efforts to develop cost-effective strategies for maximizing crop yield and quality. In this context, we investigated the amelioration of Cr(VI) toxicity through β-pinene in experimental dome simulating natural field conditions. The protective role of β-pinene was determined on physiology, morphology and ultrastructure in Zea mays under Cr(VI) stress (250 and 500 μM). Results exhibited a marked reduction in the overall growth (shoot and root length and dry matter) of Z. mays plants subjected to Cr(VI) stress. Photosynthetic pigments (chlorophyll and carotenoids) were evidently reduced, and there was a loss of membrane integrity. Supplementation of β-pinene (100 μM), however, declined the toxicity induced by Cr(VI). Interestingly, Cr-tolerant abilities were improved in relation to plant growth, photosynthetic pigments and membrane integrity with the combined treatment of Cr(VI) and β-pinene. β-Pinene also reduced the root-mediated uptake of Cr(VI) and translocation to shoots. Moreover, significant ultrastructural damages recorded in roots and shoots under Cr(VI) stress were partially reverted upon addition of β-pinene. Our analyses revealed that β-pinene mitigates Cr(VI) toxicity in Z. mays, either by membrane stabilization or serving as a barrier to the uptake of Cr from soil. Thus, exogenous supply of β-pinene can be an effective alternative to mitigate Cr toxicity in soil. However, it is deemed essential to investigate further the responses throughout the life cycle of the plant on β-pinene supplementation under natural conditions.

Phytotoxicity of Essential Oils: Opportunities and Constraints for the Development of Biopesticides. A Review

The extensive use of chemical pesticides leads to risks for both the environment and human health due to the toxicity and poor biodegradability that they may present. Farmers therefore need alternative agricultural practices including the use of natural molecules to achieve more sustainable production methods to meet consumer and societal expectations. Numerous studies have reported the potential of essential oils as biopesticides for integrated weed or pest management. However, their phytotoxic properties have long been a major drawback for their potential applicability (apart from herbicidal application). Therefore, deciphering the mode of action of essential oils exogenously applied in regards to their potential phytotoxicity will help in the development of biopesticides for sustainable agriculture. Nowadays, plant physiologists are attempting to understand the mechanisms underlying their phytotoxicity at both cellular and molecular levels using transcriptomic and metabolomic tools. This review systematically discusses the functional and cellular impacts of essential oils applied in the agronomic context. Putative molecular targets and resulting physiological disturbances are described. New opportunities regarding the development of biopesticides are discussed including biostimulation and defense elicitation or priming properties of essential oils.

A flavonone pinocembroside inhibits Penicillium italicum growth and blue mold development in 'Newhall' navel oranges by targeting membrane damage mechanism

Blue mold caused by Penicillium italicum is an important postharvest disease of citrus fruit. The antifungal activity of a flavonone pinocembroside compound obtained from the fruit of Ficus hirta Vahl., was evaluated against P. italicum. Pinocembroside showed antifungal activity against in vitro mycelial growth of P. italicum, with the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 200 and 800 mg/L, respectively. The blue mold development on 'Newhall' navel oranges was inhibited by pinocembroside in a dose-dependent manner. Moreover, pinocembroside might exert its antifungal activity via membrane-targeted mechanism with increasing membrane permeability, reduction of antioxidant enzyme activity and acceleration of lipid peroxidation in the pathogen. This pioneering study suggested that pinocembroside suppressed postharvest blue mold by direct inhibition of P. italicum mycelial growth via membrane-targeting mechanism, thus providing a novel mode of action against traditional fungicides for controlling blue mold of citrus fruit.

Phytotoxic Effects of Commercial Eucalyptus citriodora, Lavandula angustifolia, and Pinus sylvestris Essential Oils on Weeds, Crops, and Invasive Species

Background: essential oils are well known for their pharmacological effectiveness as well as their repellent, insecticide, and herbicide activities. The emergence of resistant weeds, due to the overuse of synthetic herbicides, makes it necessary to find natural alternatives for weed control. The aim of this study was to evaluate the phytotoxic effects of Eucalyptus citriodora, Lavandulaangustifolia, and Pinus sylvestris, three common commercial essential oils, on weeds (Portulaca oleracea, Lolium multiflorum, and Echinochloa crus-galli), food crops (tomato and cucumber), and the invasive species Nicotiana glauca. Methods: to determine herbicidal effects, essential oils were tested at different concentrations (0.125–1 µL/mL). The index of germination and seedling length data were recorded over 14 days. Results: the in vitro assays showed that L. angustifolia with linalool (38.7 ± 0.1%), 1,8-cineole (26.5 ± 0.1%), and camphor (14.2 ± 0.1%) as the main compounds showed the most phytotoxic effects affecting seed germination in weeds and tomato, and the aforementioned invasive species. L. multiflorum was the most sensitive weed, particularly to lavender essential oil, which decreased the growth of its hypocotyl and radicle by 87.8% and 76.7%, respectively, at a dose of 1 µL/mL. Cucumber was the most resistant food crop, with no significant reduction observed in seed germination and hypocotyl growth with E. citriodora and L. angustifolia essential oils. Conclusions: lavender essential oil represents a promising candidate for the development of effective and safe herbicides in the management of L. multiflorum affecting cucumber crops.

β-Pinene moderates Cr(VI) phytotoxicity by quenching reactive oxygen species and altering antioxidant machinery in maize

We examined the possible role of monoterpene β-pinene in providing protection against Cr(VI) toxicity in maize (Zea mays). Treatment with β-pinene (10 μM) significantly alleviated Cr(VI) accumulation and recuperated Cr(VI) caused decline in root and coleoptile growth in maize. β-Pinene addition caused a decline in Cr(VI)-induced accumulation of superoxide anion, hydroxyl ion, hydrogen peroxide and confirmed by in-situ detection of ROS using histochemical localization. It suggested that the β-pinene quenches/neutralizes enhanced ROS generated under Cr(VI) exposure. β-Pinene also reduced Cr(VI)-induced electrolyte leakage, thereby suggesting its role in membrane stabilization. Further, β-pinene regulated the activity of scavenging enzymes, thereby suggesting a role in modulating Cr(VI)-induced oxidative damage. In conclusion, our results suggest that the addition of β-pinene has a protective role against Cr(VI) stress and provides resistance to maize against Cr(VI) toxicity.

The Fight Against Panax notoginseng Root-Rot Disease Using Zingiberaceae Essential Oils as Potential Weapons

The root of Panax notoginseng (P. notoginseng) is one of the most highly valuable medicinal herbs in China owing to its pronounced hemostatic and restorative properties. Despite this important fact, growing P. notoginseng is seriously limited by root-rot diseases. In studies aimed at developing a solution to this problem, environment-friendly essential oils (EOs) of five medicinal plants of the family Zingiberaceae were tested for their inhibitory effects on the growth of three main soil pathogens associated with the root-rot diseases of P. notoginseng. The results showed that the EOs of Alpinia katsumadai Hayata and Zingiber officinale Roscoe promote significant reductions in the mycelium growth of the pathogen in vitro at a concentration of 50 mg mL-1, which is much higher than that needed (5 mg mL-1) to reduce growth by the positive control, flutriafol. Furthermore, the chemical components of the two EOs were determined by using GC-MS analysis. Eucalyptol was found to account for more than 30% of the oils of the two plants, with the second major components being geranyl acetate and α-terpineol. These substances display different degrees of fungistasis in vitro. To further determine the effects of the EO of Zingiber officinale (Z. officinale) in vivo, soilless cultivation of P. notoginseng with pathogen inoculation was conducted in a greenhouse. Addition of the petroleum ether extract (approximately equal to EO) of Z. officinale to the culture matrix causes a large decrease in both the occurrence and severity of the P. notoginseng root-rot disease. The decreasing trend of net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr) were all alleviated. In addition, the activities of catalase (CAT), peroxidase (POD), and the malondialdehyde (MDA) content were also largely reduced after pathogen infection, with the root activity being higher than that of the control. Taken together, the findings reveal that the EOs from plants might serve as promising sources of eco-friendly natural pesticides with less chemical resistance.

Bioherbicides: Current knowledge on weed control mechanism

Weed control is a challenging event during crop cultivation. Integrated management, including the application of bioherbicides, is an emerging method for weed control in sustainable agriculture. Plant extracts, allelochemicals and some microbes are utilized as bioherbicides to control weed populations. Bioherbicides based on plants and microbes inhibit the germination and growth of weeds; however,few studies conducted in weed physiology. This review ascribes the current knowledge of the physiological changes in weeds that occur during the exposure to bioherbicides. Plant extracts or metabolites are absorbed by weed seeds, which initiates damage to the cell membrane, DNA, mitosis, amylase activity and other biochemical processes and delays or inhibits seed germination. The growth of weeds is also retarded due to low rates of root-cell division, nutrient uptake, photosynthetic pigment synthesis, and plant growth hormone synthesis, while the productions of reactive oxygen species (ROS) and stress-mediated hormones increase, including irregular antioxidant activity. However, lytic enzymes and toxic substances secreted from microbes degrade the weed seed coat and utilize the endosperm for survival, which inhibits seed germination. The microbes grow through the intercellular spaces to reach the root core, and the deposition of toxins in the cells affects cell division and cellular functions. Some of the metabolites of deleterious microbes cause disease, necrosis and chlorosis,which inhibit the germination and growth of weed seeds by suppressing photosynthesis and gibberellin activities and enhancing ROS, abscisic acid and ethylene. This review explains the effects of bioherbicides (derived from plants and microbes) on weed-plant physiology to elucidate their modes of action.

An Integrative Volatile Terpenoid Profiling and Transcriptomics Analysis for Gene Mining and Functional Characterization of AvBPPS and AvPS Involved in the Monoterpenoid Biosynthesis in Amomum villosum

Amomum villosum, also known as Fructus Amomi, has been used to treat digestive diseases such as abdominal pain, vomiting, and dysentery. Volatile terpenoids are the active metabolites in the essential oil of Fructus Amomi. Nevertheless, downstream genes responsible for activating metabolites biosynthesis in A. villosum still remain unclear. Here, we report the use of an integrative volatile terpenoid profiling and transcriptomics analysis for mining the corresponding genes involved in volatile terpenoid biosynthesis. Ten terpene synthase (TPS) genes were discovered, and two of them were cloned and functionally characterized. AvTPS1 (AvPS: pinene synthase) catalyzed GPP to form α-pinene and β-pinene; AvTPS3 (AvBPPS: bornyl diphosphate synthase) produced bornyl diphosphate as major product and the other three monoterpenoids as minor products. Metabolite accumulation and gene expression pattern combined with AvPS biochemical characterization suggested that AvPS might play a role in biotic defense. On the other hand, the most active ingredient, bornyl acetate, was highly accumulated in seeds and was consistent with the high expression of AvBPPS, which further indicated that AvBPPS is responsible for the biosynthesis of bornyl acetate, the final metabolite of bornyl diphosphate in A. villosum. This study can be used to improve the quality of A. villosum through metabolic engineering, and for the sustainable production of bornyl acetate in heterologous hosts.

Neurotoxic Effects of Linalool and β-Pinene on Tribolium castaneum Herbst

Effective, ethical pest control requires the use of chemicals that are highly specific, safe, and ecofriendly. Linalool and β-pinene occur naturally as major constituents of the essential oils of many plant species distributed throughout the world, and thus meet these requirements. These monoterpenes were tested as repellents against Tribolium castaneum, using the area preference method, after four hours of exposure and the effect transcriptional of genes associated with neurotransmission. Changes in gene expression of acetylcholinesterase (Ace1), GABA-gated anion channel splice variant 3a6a (Rdl), GABA-gated ion channel (Grd), glutamate-gated chloride channel (Glucl), and histamine-gated chloride channel 2 (Hiscl2) were assessed and the interaction with proteins important for the insect using in silico methods was also studied. For linalool and β-pinene, the repellent concentration 50 (RC₅₀) values were 0.11 µL/cm² and 0.03 µL/cm², respectively. Both compounds induced overexpression of Hiscl2 gen in adult insects, and β-pinene also promoted the overexpression of Grd and the Ace1 gene. However, β-pinene and linalool had little potential to dock on computer-generated models for GABA-gated ion channel LCCH3, nicotinic acetylcholine receptor subunits alpha1 and alpha2, and putative octopamine/tyramine receptor proteins from T. castaneum as their respective binding affinities were marginal, and therefore the repellent action probably involved mechanisms other than direct interaction with these targets. Results indicated that β-pinene was more potent than linalool in inducing insect repellency, and also had a greater capacity to generate changes in the expression of genes involved in neuronal transmission.

Octanal inhibits spore germination of Penicillium digitatum involving membrane peroxidation

Octanal is a potential alternative to chemical fungicides in controlling postharvest disease of citrus fruit. In this study, the antifungal activity and the underlying mechanism of octanal against spore germination of Penicillium digitatum, one of the main postharvest pathogens in citrus, were investigated. Results showed that octanal at different concentrations (0, 0.25, 0.50, 1.00, 2.00 μl/ml) inhibited the growth of P. digitatum spores in a dose-dependent manner. The morphology and the membrane permeability of P. digitatum spores were visibly altered by 0.25 and 2.00 μl/ml of octanal. Meanwhile, octanal decreased the total lipids contents of P. digitatum spores, indicating that the membrane integrity is damaged. Furthermore, octanal apparently induced the massive accumulation of total malonaldehyde (MDA) and the reactive oxygen species (ROS). An increase in the activities of lipoxygenase (LOX), NADH oxidase, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) was also observed. These results suggested that a membrane damage mechanism involving membrane peroxidation might contribute to the antifungal activity of octanal against P. digitatum spores.

Physiological Mechanisms Only Tell Half Story: Multiple Biological Processes are involved in Regulating Freezing Tolerance of Imbibed Lactuca sativa Seeds

The physiological mechanisms by which imbibed seeds survive freezing temperatures in their natural environment have been categorized as freezing avoidance by supercooling and freezing tolerance by extracellular freeze-desiccation, but the biochemical and molecular mechanisms conferring seed freezing tolerance is unexplored. In this study, using imbibed Lactuca sativa seeds we show that fast cooled seeds (60 °C h-1) suffered significantly higher membrane damage at temperature between -20 °C and -10 °C than slow cooled (3 °Ch-1) seeds (P < 0.05), presumably explaining viability loss during fast cooling when temperature approaches -20 °C. Total soluble sugars increase in low temperature environment, but did not differ significantly between two cooling rates (P > 0.05). However, both SOD activity and accumulation of free proline were induced significantly after slow cooling to -20 °C compared with fast cooling. RNA-seq demonstrated that multiple pathways were differentially regulated between slow and fast cooling. Real-time verification of some differentially expressed genes (DEGs) revealed that fast cooling caused mRNA level changes of plant hormone and ubiquitionation pathways at higher sub-zero temperature, whilst slow cooling caused mRNA level change of those pathways at lower sub-zero ttemperatures. Thus, we conclude that imbibed seed tolerate low temperature not only by physiological mechanisms but also by biochemical and molecular changes.

Constitutive expression of CaPLA1 conferred enhanced growth and grain yield in transgenic rice plants

Phospholipids are not only important components of cell membranes, but participate in diverse processes in higher plants. In this study, we generated Capsicum annuum phospholipiase A1 (CaPLA1) overexpressing transgenic rice (Oryza sativa L.) plants under the control of the maize ubiquitin promoter. The T4 CaPLA1-overexpressing rice plants (Ubi:CaPLA1) had a higher root:shoot mass ratio than the wild-type plants in the vegetative stage. Leaf epidermal cells from transgenic plants had more cells than wild-type plants. Genes that code for cyclin and lipid metabolic enzymes were up-regulated in the transgenic lines. When grown under typical paddy field conditions, the transgenic plants produced more tillers, longer panicles and more branches per panicle than the wild-type plants, all of which resulted in greater grain yield. Microarray analysis suggests that gene expressions that are related with cell proliferation, lipid metabolism, and redox state were widely altered in CaPLA1-overexpressing transgenic rice plants. Ubi:CaPLA1 plants had a reduced membrane peroxidation state, as determined by malondialdehyde and conjugated diene levels and higher peroxidase activity than wild-type rice plants. Furthermore, three isoprenoid synthetic genes encoding terpenoid synthase, hydroxysteroid dehydrogenase and 3-hydroxy-3-methyl-glutaryl-CoA reductase were up-regulated in CaPLA1-overexpressing plants. We suggest that constitutive expression of CaPLA1 conferred increased grain yield with enhanced growth in transgenic rice plants by alteration of gene activities related with cell proliferation, lipid metabolism, membrane peroxidation state and isoprenoid biosynthesis.

Biochemical Adaptations in Zea mays Roots to Short-Term Pb(2+) Exposure: ROS Generation and Metabolism

The present study investigated the effect of lead (0, 16, 40 and 80 mg L(-1) Pb2+) exposure for 3, 12 and 24 h on root biochemistry in hydroponically grown Zea mays (maize). Pb2+ exposure (80 mg L(-1)) enhanced malondialdehyde content (239%-427%), reactive carbonyl groups (425%-512%) and H2O2 (129%-294%) accumulation during 3-24 h of treatment, thereby indicating cellular peroxidation and oxidative damage. The quantitative estimations were in accordance with in situ detection of ROS generation (using 2',7'-dichlorodihydrofluorescein diacetate dye) and H2O2 accumulation. Pb2+ treatment significantly reduced ascorbate and glutathione content during 3-24 h of exposure. On the contrary, levels of non-protein thiols were enhanced by 3-11.8 time over control in response to 16-80 mg L(-1) Pb2+ treatment, after 24 h. A dose-dependent induction in ascorbate peroxidase and lipoxygenase enzyme activity was observed in Z. mays roots. The activities of ascorbate-recycling enzymes (dehydroascorbate reductase and monodehydroascorbate reductase) were significantly increased in relation to concentration and duration of Pb2+ treatment. The study concludes that Pb2+-exposure induces ROS-mediated oxidative damage during early period of exposure despite the upregulation of enzymes of ascorbate-glutathione cycle.

Screening and identification of phytotoxic volatile compounds in medicinal plants and characterizations of a selected compound, eucarvone

Screening and identification of phytotoxic volatile compounds were performed using 71 medicinal plant species to find new natural compounds, and the characterization of the promising compound was investigated to understand the mode of action. The volatile compounds from Asarum sieboldii Miq. showed the strongest inhibitory effect on the hypocotyl growth of lettuce seedlings (Lactuca sativa L.cv. Great Lakes 366), followed by those from Schizonepeta tenuifolia Briquet and Zanthoxylum piperitum (L.) DC.. Gas chromatography-mass spectrometry (GC/MS) identified four volatile compounds, α-pinene (2,6,6-trimethylbicyclo[3.1.1]hept-2-ene), β-pinene (6,6-dimethyl-2-methylenebicyclo[3.1.1]heptane), 3-carene (3,7,7-trimethylbicyclo[4.1.0]hept-3-ene), and eucarvone (2,6,6-trimethy-2,4-cycloheptadien-1-one), from A. sieboldii, and three volatile compounds, limonene (1-methyl-4-(1-methylethenyl)-cyclohexene), menthone (5-methyl-2-(propan-2-yl)cyclohexan-1-one), and pulegone (5-methyl-2-propan-2-ylidenecyclohexan-1-one), from S. tenuifolia. Among these volatile compounds, eucarvone, menthone, and pulegone exhibited strong inhibitory effects on both the root and shoot growth of lettuce seedlings. Eucarvone-induced growth inhibition was species-selective. Cell death, the generation of reactive oxygen species (ROS), and lipid peroxidation were induced in susceptible finger millet seedlings by eucarvone treatment, whereas this compound (≤158 μM) did not cause the increase of lipid peroxidation and ROS production in tolerant maize. The results of the present study show that eucarvone can have strong phytotoxic activity, which may be due to ROS overproduction and subsequent oxidative damage in finger millet seedlings.

Eugenol-inhibited root growth in Avena fatua involves ROS-mediated oxidative damage

Plant essential oils and their constituent monoterpenes are widely known plant growth retardants but their mechanism of action is not well understood. We explored the mechanism of phytotoxicity of eugenol, a monoterpenoid alcohol, proposed as a natural herbicide. Eugenol (100-1000 µM) retarded the germination of Avena fatua and strongly inhibited its root growth compared to the coleoptile growth. We further investigated the underlying physiological and biochemical alterations leading to the root growth inhibition. Eugenol induced the generation of reactive oxygen species (ROS) leading to oxidative stress and membrane damage in the root tissue. ROS generation measured in terms of hydrogen peroxide, superoxide anion and hydroxyl radical content increased significantly in the range of 24 to 144, 21 to 91, 46 to 173% over the control at 100 to 1000 µM eugenol, respectively. The disruption in membrane integrity was indicated by 25 to 125% increase in malondialdehyde (lipid peroxidation byproduct), and decreased conjugated diene content (~10 to 41%). The electrolyte leakage suggesting membrane damage increased both under light as well as dark conditions measured over a period from 0 to 30 h. In defense to the oxidative damage due to eugenol, a significant upregulation in the ROS-scavenging antioxidant enzyme machinery was observed. The activities of superoxide dismutases, catalases, ascorbate peroxidases, guaiacol peroxidases and glutathione reductases were elevated by ~1.5 to 2.8, 2 to 4.3, 1.9 to 5.0, 1.4 to 3.9, 2.5 to 5.5 times, respectively, in response to 100 to 1000 µM eugenol. The study concludes that eugenol inhibits early root growth through ROS-mediated oxidative damage, despite an activation of the antioxidant enzyme machinery.

Susceptibility to Verticillium longisporum is linked to monoterpene production by TPS23/27 in Arabidopsis

The fungus Verticillium longisporum is a soil-borne plant pathogen of increasing economic importance, and information on plant responses to it is limited. To identify the genes and components involved in the early stages of infection, transcripts in roots of V. longisporum-challenged Arabidopsis Col-0 and the susceptible NON-RACE SPECIFIC DISEASE RESISTANCE 1 (ndr1-1) mutant were compared using ATH1 gene chips. The analysis revealed altered transcript levels of several terpene biosynthesis genes, including the monoterpene synthase TPS23/27. When transgenic 35S:TPS23/27 and TPS23/27-amiRNA plants were monitored the over-expresser line showed enhanced fungal colonization whereas the silenced genotype was indistinguishable from Col-0. Transcript analysis of terpene biosynthesis genes suggested that only the TPS23/27 pathway is affected in the two transgenic genotypes. To confirm changes in monoterpene production, emitted volatiles were determined using solid-phase microextraction and gas chromatography-mass spectrometry. Levels of all identified TPS23/27 monoterpene products were significantly altered in the transgenic plants. A stimulatory effect on conidial germination and hyphal growth of V. longisporum was also seen in co-cultivation with 35S:TPS23/27 plants and upon exposure to 1,8-cineole, the main product of TPS23/27. Methyl jasmonate treatments of myc2-1 and myc2-2 mutants and analysis of TPS23/27:uidA in the myc2-2 background suggested a dependence on jasmonic acid mediated by the transcription factor MYC2. Taken together, our results show that TPS23/27-produced monoterpenes stimulate germination and subsequent invasion of V. longisporum in Arabidopsis roots.

Rapid discrimination and feature extraction of three Chamaecyparis species by static-HS/GC-MS

This study aimed to develop a rapid and accurate analytical method for discriminating three Chamaecyparis species (C. formosensis, C. obtusa, and C. obtusa var. formosana) that could not be easily distinguished by volatile compounds. A total of 23 leaf samples from three species were analyzed by static-headspace (static-HS) coupled with gas chromatography-mass spectrometry (GC-MS). The static-HS procedure, whose experimental parameters were properly optimized, yielded a high Pearson correlation-based similarity between essential oil and VOC composition (r = 0.555-0.999). Thirty-six major constituents were identified; along with the results of cluster analysis (CA), a large variation in contents among the three different species was observed. Principal component analysis (PCA) methods illustrated graphically the relationships between characteristic components and tree species. It was clearly demonstrated that the static-HS-based procedure enhanced greatly the speed of precise analysis of chemical fingerprint in small sample amounts, thus providing a fast and reliable tool for the prediction of constituent characteristics in essential oil, and also offering good opportunities for studying the role of these feature compounds in chemotaxonomy or ecophysiology.