Effects of acid and aluminum stress on seed germination and physiological characteristics of seedling growth in Sophora davidii

Sophora davidii, a vital forage species, predominantly thrives in the subtropical karst mountains of Southwest China. Its resilience to poor soil conditions and arid environments renders it an ideal pioneer species for ecological restoration in these regions. This study investigates the influence of acidic, aluminum-rich local soil on the germination and seedling growth physiology of S. davidii. Experiments were conducted under varying degrees of acidity and aluminum stress, employing three pH levels (3.5 to 5.5) and four aluminum concentrations (0.5 to 2.0 mmol·L-1). The results showed that germination rate, germination index, and vigor index of S. davidii seeds were decreased but not significantly under slightly acidic conditions (pH 4.5-5.5), while strong acid (pH = 3.5) significantly inhibited the germination rate, germination index, and vigor index of white spurge seeds compared with the control group. Aluminum stress (≥0.5 mmol·L-1) significantly inhibited the germination rate, germination index, and vigor index of S. davidii seed. Moreover, the seedlings' root systems were sensitive to the changes of aluminum concentration, evident from significant root growth inhibition, characterized by root shortening and color deepening. Notably, under aluminum stress (pH = 4.3), the levels of malondialdehyde and proline in S. davidii escalated with increasing aluminum concentration, while antioxidant enzyme activities demonstrated an initial increase followed by a decline. The study underscores the pivotal role of cellular osmoregulatory substances and protective enzymes in combating aluminum toxicity in S. davidii, a key factor exacerbating growth inhibition in acidic environments. These findings offer preliminary theoretical insights for the practical agricultural utilization of S. davidii in challenging soil conditions.

Identification of novel candidate loci and genes for seed vigor-related traits in upland cotton (Gossypium hirsutum L.) via GWAS

Seed vigor (SV) is a crucial trait determining the quality of crop seeds. Currently, over 80% of China's cotton-planting area is in Xinjiang Province, where a fully mechanized planting model is adopted, accounting for more than 90% of the total fiber production. Therefore, identifying SV-related loci and genes is crucial for improving cotton yield in Xinjiang. In this study, three seed vigor-related traits, including germination potential, germination rate, and germination index, were investigated across three environments in a panel of 355 diverse accessions based on 2,261,854 high-quality single-nucleotide polymorphisms (SNPs). A total of 26 significant SNPs were detected and divided into six quantitative trait locus regions, including 121 predicted candidate genes. By combining gene expression, gene annotation, and haplotype analysis, two novel candidate genes (Ghir_A09G002730 and Ghir_D03G009280) within qGR-A09-1 and qGI/GP/GR-D03-3 were associated with vigor-related traits, and Ghir_A09G002730 was found to be involved in artificial selection during cotton breeding by population genetic analysis. Thus, understanding the genetic mechanisms underlying seed vigor-related traits in cotton could help increase the efficiency of direct seeding by molecular marker-assisted selection breeding.

Germination and seedling growth of Calluna vulgaris is sensitive to regional climate, heathland succession, and drought

The coastal heathlands of Northwest Europe are highly valued cultural landscapes, that are critically endangered due to land use and climatic changes, such as increased frequency and severity of drought events. Our study is the first to assess how the germination and early seedling growth of Calluna vulgaris respond to drought. In a factorial design field experiment, we exposed maternal plants to three in-situ drought treatments (control, 60%, 90% roof coverage), across three successional stages after fire (pioneer, building, mature), and two regions (60°N, 65°N). Seeds from 540 plants within the experiment were, weighed, and exposed to five water potentials, ranging from -0.25 to -1.7 MPa, in a growth chamber experiment. We recorded germination (percentage, rate), seedling growth (above- vs. belowground allocation), and seedling functional traits (specific leaf area [SLA], specific root length [SRL]). Overall variation in germination between regions, successional stages, and maternal drought treatments was largely mediated by variation in seed mass. Plants from the northernmost region had higher seed mass and germination percentages. This is indicative of higher investment in seeds, likely linked to the populations' absence of vegetative root sprouting. Seeds from the mature successional stage germinated to lower final percentages than those from earlier successional stages, especially when the maternal plants had been exposed to drought (60% and 90% roof coverage). Exposure to reduced water availability decreased germination percentage and increased the time to 50% germination. Seedlings fully developed in the range -0.25 to -0.7 MPa, with increased root:shoot and lower SRL during reduced water availability, suggesting a resource-conservative response to drought during the early stages of development. Our results thus suggest a sensitivity to drought during the germination and seedling life-history stages that may reduce Calluna's ability to re-establish from seeds as the incidence and severity of droughts are projected to increase under future climates.

Mapping the Genomic Regions Controlling Germination Rate and Early Seedling Growth Parameters in Rice

Seed vigor is the key performance parameter of good quality seed. A panel was prepared by shortlisting genotypes from all the phenotypic groups representing seedling growth parameters from a total of 278 germplasm lines. A wide variation was observed for the traits in the population. The panel was classified into four genetic structure groups. Fixation indices indicated the existence of linkage disequilibrium in the population. A moderate to high level of diversity parameters was assessed using 143 SSR markers. Principal component, coordinate, neighbor-joining tree and cluster analyses showed subpopulations with a fair degree of correspondence with the growth parameters. Marker-trait association analysis detected eight novel QTLs, namely qAGR4.1, qAGR6.1, qAGR6.2 and qAGR8.1 for absolute growth rate (AGR); qRSG6.1, qRSG7.1 and qRSG8.1 for relative shoot growth (RSG); and qRGR11.1 for relative growth rate (RGR), as analyzed by GLM and MLM. The reported QTL for germination rate (GR), qGR4-1, was validated in this population. Additionally, QTLs present on chromosome 6 controlling RSG and AGR at 221 cM and RSG and AGR on chromosome 8 at 27 cM were detected as genetic hotspots for the parameters. The QTLs identified in the study will be useful for improvement of the seed vigor trait in rice.

Deep-learning-based automatic evaluation of rice seed germination rate

BACKGROUND

Rice is an important food crop plant in the world and is also a model plant for genetics and breeding research. The germination rate is an important indicator that measures the performance of rice seeds. Currently, solutions involving image processing techniques have substantial challenges in the identification of seed germination. The detection of rice seed germination without human intervention involves challenges because the rice seeds are small and densely distributed.

RESULTS

In this article, we develop a convolutional neural network (YOLO-r) that can detect the germination status of rice seeds and automatically evaluate the total number of germinations. Image partition, the Transformer encoder, a small target detection layer, and CDIoU loss are exploited in YOLO-r to improve the detection accuracy. A total of 21 429 seeds were collected, which have different phenotypic characteristics in length, shape, and color. The results show that the mean average precision of YOLO-r is 0.9539, which is higher than the compared models. Moreover, the average detection time per image of YOLO-r was 0.011 s, which meets the real-time requirements. The experimental results demonstrate that YOLO-r is robust to complex situations such as water stains, impurities, awns, adhesion, and so on. The results also show that the mean absolute error of the predicted germination rate mainly exists within 0.1.

CONCLUSIONS

Numerous experimental studies have demonstrated that YOLO-r can predict rice germination rate in a fast, easy, and accurate manner. © 2022 Society of Chemical Industry.

Soil Quality Enhances Seed Germination Success in Ephedra major-A Pilot Experiment

There are currently knowledge gaps in the environmental context related to successful seed germination of Ephedra major. Therefore, we herein explore the influence of soil quality and water availability on the germination performance through a garden experiment that mimics natural site conditions. One hundred seeds were extracted from fifty ripe strobili collected randomly from the ramets of a single female plant. Ten seeds per pot were sown in ten pots, which were equally split by receiving different watering treatments (watered versus control) and soil types (S0-shallow and stony; S1-like S0 but slightly deeper; S2-like S0 but even deeper and rich in woodland humus; S3-clay-layered alluvial; S4-anthropogenic). No significant interaction effect was detected between the two manipulated factors. Watering only had a marginal effect on the germination rate, but the latter was significantly higher in S2 when compared to the other soil types. These outcomes suggest that soil quality is more important than moisture for the germination success. Its rate is expected to be higher under the open canopy of woodlands compared to open rupicolous habitats, since seeds can benefit from higher humus availability and reduced evapotranspiration.

Quantitative trait locus mapping and candidate gene analysis for salt tolerance at bud stage in rice

Soil salinization has a serious influence on rice yield and quality. How to enhance salt tolerance in rice is a topical issue. In this study, 120 recombinant inbred line populations were generated through nonstop multi-generation selfing using a male indica rice variety Huazhan (Oryza sativa L. subsp. indica cv. 'HZ') and a female variety of Nekken2 (Oryza sativa L. subsp. japonica cv. 'Nekken2') as the parents. Germination under 80 mM NaCl conditions was measured and analyzed, and quantitative trait locus (QTL) mapping was completed using a genetic map. A total of 16 salt-tolerance QTL ranges were detected at bud stage in rice, which were situated on chromosomes 3, 4, 6, 8, 9, 10, 11, and 12. The maximum limit of detection was 4.69. Moreover, the qST12.3 was narrowed to a 192 kb region on chromosome 12 using map-based cloning strategy. Statistical analysis of the expression levels of these candidate genes under different NaCl concentrations by qRT-PCR revealed that qST12.3 (LOC_Os12g25200) was significantly down-regulated with increasing NaCl concentration, and the expression level of the chlorine-transporter-encoding gene LOC_Os12g25200 in HZ was significantly higher than that of Nekken2 under 0 mM NaCl. Sequencing analysis of LOC_Os12g25200 promoter region indicated that the gene expression difference between parents may be due to eight base differences in the promoter region. Through QTL mining and analysis, a plurality of candidate genes related to salt tolerance in rice was obtained, and the results showed that LOC_Os12g25200 might negatively regulate salt tolerance in rice. The results provide the basis for further screening and cultivation of salt-tolerant rice varieties and have laid the foundation for elucidating further molecular regulation mechanisms of salt tolerance in rice.

Research Progress on Dormancy Mechanism and Germination Technology of Kobresia Seeds

Kobresia is a subfamily of Cyperaceae, a perennial herbaceous plant that stores a large amount of organic carbon and nutrients (nitrogen, phosphorus, etc.) in the soil. This type of grass is soft and appreciated by all kinds of farm animals. It is one of the predominantly excellent fodder on the Qinghai-Tibet Plateau. Its good growth plays an important role in developing the local economy and maintaining ecological balance on the Qinghai-Tibet Plateau as well. The main objectives of this review are to systematically present and analyze the factors responsible for the low germination rate of Kobresia and to analyze the physical and chemical methods that are used in order to alleviate dormancy and to improve the germination rate of Kobresia seeds. This is performed in order to lay the foundation for future research in this field. At the same time, we have analyzed the research deficiencies and formulated recommendations for the future. This review will provide comprehensive information in order to reduce the cost of planting Kobresia, as well as to provide theoretical support and technical guidance for the purposes of ecosystem restoration and livestock development.

Improving Ultra-Low Temperature Preservation Technologies of Soybean Pollen for Off-Season and Off-Site Hybridization

Preserving viable pollen is of great interest to breeders to maintain desirable germplasm for future inbreeding. Ultra-low temperature preservation of pollen is an effective and safe way for long-term storage of plant germplasm resources. In this study, we improved methods for the preservation of soybean pollen at ultra-low temperature. Soybean flowers at the initially-open stage were collected at 6-10 a.m. during the fully-bloom stage of soybean plants and were dehydrated for 10 h and then frozen and stored at -196 or -80°C. In vitro culture experiments showed that the viability of preserved pollen remained as high as about 90%. The off-season (local site Heihe) and off-site (Beijing, after long-distance express delivery from Heihe) hybridization verification was conducted, and no significant difference in true hybrid rate was founded between the preserved pollen and the fresh pollen. The ultra-low temperature preservation technology for soybean pollen could break the spatiotemporal limit of soybean hybridization and facilitate the development of engineered soybean breeding.

[Seed morphology and germination characteristics of Tripterygium wilfordii]

The seeds of Tripterygium wilfordii are characterized by dormancy and a long germination cycle under natural sowing conditions. In this study, we developed a method for rapid germination of T. wilfordii seeds by analyzing the size, morphology, thousand-grain weight, viability, moisture content, physicochemical properties, and seed germination rates under different germination conditions. The seeds of T. wilfordii were fine columnar with a thick and hard outer seed coat. They had the length of 6.69 mm, the width of 2.14 mm, the thickness of 1.68 mm, the thousand-grain weight of 8.99 g, the moisture content of 8.86%, the soluble sugar content of 21.3 mg·g~(-1), the starch content of 28.9 mg·g~(-1), the soluble protein content of 44.2 mg·g~(-1), and the seed viability of only 54.0%. The seeds were respectively treated with distilled water, ultrasonication, low-temperature storage, 50 ℃ water, 100 mg·L~(-1) 6-BA, 0.6% KMnO_4, 1% KNO_3, 50 mg·L~(-1) NAA, and 100 mg·L~(-1) GA_3 solution. The results showed that soaking the seeds in 100 mg·L~(-1) GA_3 solution significantly promoted the germination. Further, the seeds were soaked in 50, 100, 250, 500, and 1 000 mg·L~(-1) GA_3 solutions, which demonstrated that high concentration(500 mg·L~(-1), 1 000 mg·L~(-1)) of GA_3 solutions increased the germination rate and speed and shortened the germination cycle from more than 3 months to less than 15 days. The findings of this study are of great significance to the breeding of T. wilfordii and lay a foundation for the large-scale propagation of T. wilfordii seeds and the excavation of T. wilfordii germplasm resources.

Methods for Assessment of Viability and Germination of Plasmodiophora brassicae Resting Spores

Clubroot caused by the obligate biotrophic parasite Plasmodiophora brassicae is a destructive soil borne disease of cruciferous crops. Resting spores of P. brassicae can survive in the soil for a long period without hosts or external stimulants. The viability and germination rate of resting spores are crucial factors of the inoculum potential in the field. The accurate assessment of viability and germination rate is the foundation to evaluate the effect of control methods. In this study, we evaluated several methods for the assessment of viability and germination rate of P. brassicae resting spores. Dual staining with calcofluor white-propidium iodide (CFW-PI) or single stain with Evans blue showed reliable accuracy in estimating viability. CFW-PI was capable of reliably determining the viability within 10 min, while Evans blue required overnight incubation to obtain accurate results. Due to DNA degradation of heat treatments, acetone was selected to evaluate the efficiency of propidium monoazide (PMA)–quantitative PCR (qPCR) used for the quantification of DNA from viable cells. The staining with 4,6-Diamidine-2-phenylindole dihydrochloride (DAPI) and the use of differential interference contrast microscopy were suitable for the determination of resting spore germination rates. The latter method also allowed recording individual germination states of spores. Alternatively, dual staining with CFW-Nile red was successfully used to assess the germination rate of resting spores with a lethal pre-treatment. This study evaluates and confirms the suitability of various microscopic and molecular genetic methods for the determination of viability and germination of P. brassicae resting spores. Such methods are required to study factors in the soil regulating survival, dormancy and germination of P. brassicae resting spores causing clubroot disease in Brassicaceae hosts and therefore are fundamental to develop novel strategies of control.

Not dead yet: Diatom resting spores can survive in nature for several millennia

PREMISE

Understanding the adaptive capacities of species over long timescales lies in examining the revived recent and millennia-old resting spores buried in sediments. We show for the first time the revival, viability, and germination rate of resting spores of the diatom Chaetoceros deposited in sub-seafloor sediments from three ages (recent: 0 to 80 years; ancient: ~1250 (Medieval Climate Anomaly) and ~6600 (Holocene Thermal Maximum) calendar year before present.

METHODS

Recent and ancient Chaetoceros spores were revived to examine their viability and germination rate. Light and scanning electron microscopy and Sanger sequencing was done to identify the species.

RESULTS

We show that ~6600 cal. year BP old Chaetoceros resting spores are still viable and that the vegetative reproduction in recent and ancient resting spores varies. The time taken to germinate is three hours to 2 to 3 days in both recent and ancient spores, but the germination rate of the spores decreased with increasing age. The germination rate of the recent spores was ~41% while that of the ancient spores were ~31% and ~12% for the ~1250 and ~6600 cal. year BP old resting spores, respectively. Based on the morphology of the germinated vegetative cells we identified the species as Chaetoceros muelleri var. subsalsum. Sanger sequences of nuclear and chloroplast markers identified the species as Chaetoceros muelleri.

CONCLUSIONS

We identify a unique model system, Chaetoceros muelleri var. subsalsum and show that recent and ancient resting spores of the species buried in sediments in the Baltic Sea can be revived and used for long-term evolutionary studies.

Effects of Temperature and Salinity on Seed Germination of Three Common Grass Species

Temperature and salinity significantly affect seed germination, but the joint effects of temperature and salinity on seed germination are still unclear. To explore such effects, a controlled experiment was conducted, where three temperature levels (i.e., 15, 20, and 25°C) and five salinity levels (i.e., 0, 25, 50, 100, and 200 mmol/L) were crossed, resulting in 15 treatments (i.e., 3 temperature levels × 5 salinity levels). Three typical grass species (Festuca arundinacea, Bromus inermis, and Elymus breviaristatus) were used, and 25 seeds of each species were sown in petri dishes under these treatments. Germination percentages and germination rates were calculated on the basis of the daily recorded germinated seed numbers of each species. Results showed that temperature and salinity significantly affected seed germination percentage and germination rate, which differed among species. Specifically, F. arundinacea had the highest germination percentage, followed by E. breviaristatus and B. inermis, with a similar pattern also found regarding the accumulated germination rate and daily germination rate. Generally, F. arundinacea was not sensitive to temperature within the range of 15-25°C, while the intermediate temperature level improved the germination percentage of B. inermis, and the highest temperature level benefited the germination percentage of E. breviaristatus. Moreover, F. arundinacea was also not sensitive to salinity within the range of 0-200 mmol/L, whereas high salinity levels significantly decreased the germination percentage of B. inermis and E. breviaristatus. Thus, temperature and salinity can jointly affect seed germination, but these differ among plant species. These results can improve our understanding of seed germination in saline soils in the face of climate change.

Low-Temperature Plasma-Assisted Nitrogen Fixation for Corn Plant Growth and Development

Nitrogen fixation is crucial for plants as it is utilized for the biosynthesis of almost all biomolecules. Most of our atmosphere consists of nitrogen, but plants cannot straightforwardly assimilate this from the air, and natural nitrogen fixation is inadequate to meet the extreme necessities of global nutrition. In this study, nitrogen fixation in water was achieved by an AC-driven non-thermal atmospheric pressure nitrogen plasma jet. In addition, Mg, Al, or Zn was immersed in the water, which neutralized the plasma-treated water and increased the rate of nitrogen reduction to ammonia due to the additional hydrogen generated by the reaction between the plasma-generated acid and metal. The effect of the plasma-activated water, with and without metal ions, on germination and growth in corn plants (Zea Mays) was investigated. The germination rate was found to be higher with plasma-treated water and more efficient in the presence of metal ions. Stem lengths and germination rates were significantly increased with respect to those produced by DI water irrigation. The plants responded to the abundance of nitrogen by producing intensely green leaves because of their increased chlorophyll and protein contents. Based on this report, non-thermal plasma reactors could be used to substantially enhance seed germination and seedling growth.

Reduction of T-2 and HT-2 mycotoxins by atmospheric cold plasma and its impact on quality changes and germination of wheat grains

Wheat (Triticum aestivum) is susceptible to mycotoxin contamination, which can result in significant health risks and economic losses. This research examined the ability of air atmospheric cold plasma (air-ACP) treatment to reduce pure and spiked T-2 and HT-2 mycotoxins' concentration on wheat grains. This study also evaluated the effect of ACP treatment using different gases on wheat grain germination parameters. The T-2 and HT-2 mycotoxin solutions applied on round cover-glass were placed on microscopy slides and wheat grains (0.5 g) were individually spiked with T-2 and HT-2 on their surfaces. Samples were then dried at room temperature (∼24 °C) and treated by air-ACP for 1 to 10 min. Ten minutes of air-ACP treatment significantly reduced pure T-2 and HT-2 concentrations by 63.63% and 51.5%, respectively. For mycotoxin spiked on wheat grains, 10 min air-ACP treatment significantly decreased T-2 and HT-2 concentrations up to 79.8% and 70.4%, respectively. No significant change in the measured quality and color parameters was observed in the ACP-treated samples. Wheat grain germination parameters were not significantly different, when treated with ACP using different gases. Air-ACP treatment and ACP treatment using 80% nitrogen + 20% oxygen improved the germination of wheat grains by 10% and 6%, respectively. This study demonstrated that ACP is an innovative technology with the potential to improve the safety of wheat grains by reducing T-2/HT-2 mycotoxins with an additional advantage of improving their germination. PRACTICAL APPLICATION: Atmospheric cold plasma (ACP) technology has a huge potential to degrade mycotoxins in food grains. This study evaluated the efficacy of ACP to reduce two major mycotoxins (T-2 and HT-2 toxins) in wheat grains. The results of this study will help to develop and scale-up the ACP technology for mycotoxin degradation in grains.

Carbon Nanotubes Improved the Germination and Vigor of Plant Species from Peatland Ecosystem Via Remodeling the Membrane Lipidome

Application of the nanopriming technique to alleviate seed dormancy has shown promising results in various agricultural crop species. However, there is a dearth of knowledge regarding its potential use in native peatland boreal forest species to alleviate seed dormancy and improve their propagation or vigor for forest reclamation activities. Herein, we demonstrate the use of nanopriming with carbon nanotubes (CNT) to alleviate seed dormancy, improved seed germination, and seedling vigor in two boreal peatland species. Bog birch (Betula pumila L.) and Labrador tea (Rhododendron groenlandicum L.) seeds with embryo or seed coat dormancy were nanoprimed with either 20 or 40 µg/mL CNT, cold stratified at 2–4 °C for 15 days, and allowed to germinate at room temperature. The emerged seedlings’ lipidome was assessed to decipher the role of lipid metabolism in alleviating seed dormancy. We observed significant (p < 0.05) improvement in seedling germination and seedling vigor in seeds primed with multiwalled carbon nanotubes functionalized with carboxylic acids. Phosphatidylcholine (PC 18:1/18:3), phosphatidylglycerol (PG 16:1/18:3), and lysophosphatidylcholine (LPC 18:3) molecular species (C18:3 enriched) were observed to be highly correlated with the increased seed germination percentages and the enhanced seedling vigor. Mechanistically, it appears that carbon nanoprimed seeds following stratification are effective in mediating seed dormancy by remodeling the seed membrane lipids (C18:3 enriched PC, PG, and LPC) in both peatland boreal forest species. The study results demonstrate that nanopriming may provide a solution to resolve seed dormancy issues by enhancing seed germination, propagation, and seedling vigor in non-resource boreal forest species ideally suited for forest reclamation following anthropogenic disturbances.

Direct effects of nitrogen addition on seed germination of eight semi-arid grassland species

Seed germination plays an important role in mediating plant species composition of grassland communities under nitrogen (N) enrichment. Shifts of plant community structure with N-enhanced deposition in terrestrial ecosystems have occurred globally. Despite numerous studies about the effects of enhanced N deposition on mature plant communities, few studies have focused on seed germination. Using a laboratory experiment, we report the effects of five N concentrations, including 0, 5, 10, 20, and 40 mM N (NH4NO3) on seed germination of eight semi-arid grassland species. Results showed that low N concentrations (5- and 20-mM N) promoted mean final germination proportion of all eight species by 4.4% and 6.4%, but high concentrations (40 mM N) had no effect. The mean germination rate was decreased 2.1% and 5.1% by higher N concentration (20- and 40-mM N) levels, but germination start time showed the opposite trend, delayed by 0.7, 0.9, and 1.8 d for the 10, 20, and 40 mM N treatments. Final germination proportion, mean germination rate, and germination start time were significantly different among species in response to N concentration treatments. The final germination proportion of Allium tenuissimum and Chenopodium glaucum were suppressed by increased N concentration, whereas it increased for Potentilla bifurca, Plantago asiatica, and Setaria viridis. Our findings provide novel insights into N deposition-induced species loss based on seed germination factors in semi-arid grassland communities.

Effect of temperature, pH, physical and chemical factors on germination rate of the chlamydospores of the nematophagous fungus Duddingtonia flagrans

This study mainly investigated the effects of environmental factors on the germination/dormancy, sporulation and resistance of Duddingtonia flagrans chlamydospores. Results showed that the germination temperature of chlamydospores was >10°C and ≤35°C. After the chlamydospores were treated at -20, -40 and -80°C for 12-24 h, they still had the ability to germinate. The chlamydospores germinated at pH 3-13 but did not germinate at pH 1-2 and pH 14. The chlamydospores could tolerate ultraviolet rays for 720 min, but visible light irradiation for 24 h significantly reduced their germination rate. The chlamydospores did not germinate under anaerobic conditions. After the chlamydospores were cultured on water agar (WA) containing 5, 10 and 20% NaCl, their germination rate was significantly inhibited. Once NaCl was removed, the chlamydospores almost completely recovered their germination ability. Among the nine kinds of additives used in the study, 0.3% arginine significantly promoted spore germination (P < 0.05) but 1% trehalose and 1% glycerine significantly inhibited spore germination during incubation from 24 h to 48 h (P < 0.05). This work indicated that D. flagrans chlamydospores are highly resistant to environmental variations and so could be used for biocontrol of animal parasites.

[Effects of root extract of host plants on seed germination and haustorium formation of Cistanche deserticola]

We examined the effects of root extracts of Haloxylon ammodendron and Beta vulgaris in Chenopodiaceae extracted by water and ethanol on seed germination and haustorium formation of Cistanche deserticola by filter paper culture dish method. The results showed that only adding root extract had no effect on seed germination and haustorium formation of C. deserticola. The germination rate of C. deserticola seeds treated by adding 10 mg·kg^-1 gibberellin to the root extracted by ethanol was not significantly different from that of the control (GA₃), whereas those treated by adding gibberellin to the ethanol extract of two kinds of host root was increased by more than 10 times. The germination rate of C. deserticola seeds in the treatment with adding 1 mg·kg^-1 fluridone (FL) to root extract was not significantly different from that in the control with only fluridone, while those in the treatment with B. vulgaris root water extraction was the highest (39.4%). Compared to the treatment of adding gibberellin to the root extract, the germination rate of C. deserticola seeds was only increased. When FL was added to the host root extract, the haustorium was formed on the germination tube, with the formation rate of the ethanol extraction group being the highest (16.2%). Seed germination rate of C. deserticola increased to 52.3% when GA₃ and FL were added to the ethanol extract of H. ammodendron, but the formation rate of haustorium was not different from that of FL treatment. Only 6.7% of the seed formation haustorium in the control was significantly lower than that in FL treatment. There were differences in the position and shape of the haustorium of C. deserticola seeds under different treatments. The haustorium produced by adding the extract of the host root mostly appeared at the top of the bud tube, and many papillae raised into claws. The haustorium of FL treatment without adding the extract of the host root mostly appeared at the bottom or the top of the bud tube splitting. The results indicated that ethanol extraction and water extraction could extract the substances that could promote the formation of C. deserticola seeds haustorium from the host root, but did not affect seed germination. GA₃ and FL could significantly improve the germination rate of C. deserticola seeds, but the formation of the haustorium was affected by some substances in the host root extract.

Thermal Requirements Underpinning Germination Allude to Risk of Species Decline from Climate Warming

The storage of seeds is a commonly used means of preserving plant genetic diversity in the face of rising threats such as climate change. Here, the findings of research from the past decade into thermal requirements for germination are synthesised for more than 100 plant species from southern Western Australia. This global biodiversity hotspot is predicted to suffer major plant collapse under forecast climate change. A temperature gradient plate was used to assess the thermal requirements underpinning seed germination in both commonly occurring and geographically restricted species. The results suggest that the local climate of the seed source sites does not drive seed responses, neither is it indicative of temperatures for optimal germination. The low diurnal phase of the temperature regime provided the most significant impact on germination timing. Several species germinated optimally at mean temperatures below or close to current wet quarter temperatures, and more than 40% of species were likely to be impacted in the future, with germination occurring under supra-optimal temperature conditions. This research highlights both species vulnerability and resilience to a warming climate during the regeneration phase of the life cycle and provides vital information for those aiming to manage, conserve and restore this regional flora.

Nitric Oxide Pre-Treatment Advances Seed Germination and Alleviates Copper-Induced Photosynthetic Inhibition in Indian Mustard

This investigation tested the efficiency of nitric oxide (NO) in alleviation of Cu-induced adverse impacts on seed germination and photosynthesis in Indian mustard (Brassica juncea L.). Pre-treatment of B. juncea seeds with sodium nitroprusside (SNP; NO donor) significantly improved the seed germination rate and also alleviated Cu-accrued oxidative stress. However, in the absence of NO, Cu caused a higher reduction in seed germination rate. The presence of NO strengthened the antioxidant defense system (glutathione reductase, ascorbate peroxidase, and superoxide dismutase) and thereby sustained the lower lipid peroxidation, reduced H2O2 content, and thiobarbituric acid reactive substances in Cu-exposed seeds. NO pre-treated seeds also retained a higher amylase activity and exhibited an improved seed germination rate. This effect of NO under Cu stress was also seen in plants originated from the NO pre-treated seeds, where the role of NO pre-treatment was reflected in the improved photosynthetic potential of B. juncea. Overall, NO pre-treatment not only improved the germination rate in seeds but also carried its effects in the grown seedlings evidenced as improved photosynthesis and growth. Potential mechanisms involved in the action of NO pre-treatment included NO-mediated significant strengthening of the antioxidant defense system and decreases in Cu-caused oxidative stress parameters.

Carbon Nanoparticles Functionalized with Carboxylic Acid Improved the Germination and Seedling Vigor in Upland Boreal Forest Species

Nanopriming has been shown to significantly improve seed germination and seedling vigor in several agricultural crops. However, this approach has not been applied to native upland boreal forest species with complex seed dormancy to improve propagation. Herein, we demonstrate the effectiveness of carbon nanoparticles functionalized with carboxylic acids in resolving seed dormancy and improved the propagation of two native upland boreal forest species. Seed priming with carbon nanoparticles functionalized with carboxylic acids followed by stratification were observed to be the most effective in improving germination to 90% in green alder (Alnus viridis L.) compared to 60% in the control. Conversely, a combination of carbon nanoparticles (CNPs), especially multiwall carbon nanoparticles functionalized with carboxylic acid (MWCNT–COOH), cold stratification, mechanical scarification and hormonal priming (gibberellic acid) was effective for buffaloberry seeds (Shepherdia canadensis L.). Both concentrations (20 µg and 40 µg) of MWCNT–COOH had a higher percent germination (90%) compared to all other treatments. Furthermore, we observed the improvement in germination, seedling vigor and resolution of both embryo and seed coat dormancy in upland boreal forest species appears to be associated with the remodeling of C18:3 enriched fatty acids in the following seed membrane lipid molecular species: PC18:1/18:3, PG16:1/18:3, PE18:3/18:2, and digalactosyldiacylglycerol (DGDG18:3/18:3). These findings suggest that nanopriming may be a useful approach to resolve seed dormancy issues and improve the seed germination in non-resource upland boreal forest species ideally suited for forest reclamation following resource mining.

Flooding with shallow water promotes the invasiveness of Mikania micrantha

The invasive ability of alien plants is not only affected by their biological characteristics but also by environmental factors. Therefore, investigating the relationship between plant growth and environmental factors is helpful for predicting the invasive potential of alien species. Mikania micrantha H.B.K. (a vine of Asteraceae) is one of the top 10 most invasive weeds worldwide and causes serious damage to agroforestry ecosystems. Water is an important environmental factor that affects plant growth; however, the relationship between water conditions and the rapid growth of M. micrantha is not clear. In this study, 162 M. micrantha population sizes were investigated in dry, wet and aquatic habitats in the Pearl River Delta region of Guangdong, China. In addition, the seed germination and seedling growth characteristics of M. micrantha were determined by submerging tests. The results showed that the population size of M. micrantha was the largest in aquatic habitats, and the soil moisture content was positively correlated to the population size in dry and wet habitats. Furthermore, M. micrantha seeds could germinate underwater and grow out of the water surface at a depth of 6 cm with a survival rate of 7.4%. Aquatic habitat promoted vine elongation, whereas dry habitats resulted in the reverse pattern. After 8 weeks of water treatments, the vine stem length was 2 and 3 times longer in the aquatic habitat than the wet and dry habitats, respectively. The total root length, root volume, and root tip number increased significantly in the aquatic habitat when compared to those in the wet habitat; however, these parameters exhibited the opposite pattern in the dry habitat. The results showed that flooding with shallow water is conducive to the invasiveness of M. micrantha, suggesting that water is the key determinant during the intrusion process of M. micrantha populations.

OPEN RESEARCH BADGES

This article has been awarded Open Data, Open Materials and Preregistered research design Badges. All materials and data are publicly accessible via the Open Science Framework at https://osf.io/ksz2f/?viewonly=30b6fec21f0447edbdfc9cebe2b01065, https://osf.io/a5ymf/ and https://osf.io/ksz2fl?viewonly=cfcbfOfc829c402fb22deb3be801dffc.

Seed traits and germination behaviour of four Sardinian populations of Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) along an altitudinal gradient

Helichrysum microphyllum subsp. tyrrhenicum (Asteraceae) is an endemic taxon of Sardinia and Corsica, where it grows at different altitudes. The objective of this study was to investigate the seed traits and germination behaviour of four Sardinian populations of this taxon located at different altitudes. Seed traits were evaluated, and germination tests were carried out by incubating seeds at a range of constant (5-30 °C) and alternating (25/10 °C) temperatures. The dry after-ripening (DAR) pre-treatment was also applied by storing seed in dry conditions for 3 months at 25 °C. Seed traits and germination behaviour data were statistically analysed to identify if there was a correlation with altitude. Differences in seed size, area and mass among populations were recorded, however, no relationship was found with altitude. High germination percentages were obtained in all populations, both in untreated and DAR seeds, and were positively affected by alternating temperatures. The final germination percentage and time required to reach 50% final germination (T₅₀ ) showed no relationship with altitude. The differences in seed traits and germination detected among the studied populations of H. microphyllum subsp. tyrrhenicum were not correlated with altitude. This study provides new and important knowledge for this taxon. H. microphyllum subsp. tyrrhenicum is characterised by high germination percentages and low T₅₀ values and does not seem to require any dormancy-breaking treatment. This species represents a high-potential native plant species that should be considered within environmental management plans.

Exposure to Ultraviolet (UV-C) Radiation Increases Germination Rate of Maize (Zea maize L.) and Sugar Beet (Beta vulgaris) Seeds

This study investigated the effect of ultraviolet (UV-C) radiation on the germination percentage, germination rate, radicle length, and plumule length of maize and sugar beet seeds. The experiment was implemented in six replicates of 30 seeds per replicate and in sterilized petri dishes under laboratory conditions. Treatments included UV-C (254 nm) radiation exposure durations of 0 min (control), 30 min, 2 h, 4 h, 8 h, and 12 h. The UV-C radiation treatments did not significantly affect the germination percentage of the seeds (p < 0.05). However, the seeds germination rate was significantly affected by the UV-C radiation treatments. The treatments of 8 h and 12 h exposure duration led to the highest seed germination rates in maize and sugar beet, respectively. Lowest seed germination rates belonged to the controls. The radicle length of maize seeds was significantly affected by the UV-C radiation treatments, but the treatments did not significantly affect the radicle length of sugar beet seeds. The 12 h exposure to UV-C radiation treatment resulted in the largest radicle in maize, which was 2.08 cm larger than the radicle of the control seeds. The UV-C radiation treatments had a statistically significant effect on the plumule length of maize and sugar beet seeds. The treatment 8 h UV-C exposure duration led to the largest plumule in maize and sugar beet, which were 0.32 cm and 0.83 cm larger than the plumule of the control seeds, respectively. Breaking down the seed coat and increasing the temperature by UV-C radiation are potential reasons for the observed positive effects.

Use of auto-germ to model germination timing in the sagebrush-steppe

Germination timing has a strong influence on direct seeding efforts, and therefore is a closely tracked demographic stage in a wide variety of wildland and agricultural settings. Predictive seed germination models, based on soil moisture and temperature data in the seed zone are an efficient method of estimating germination timing. We utilized Visual Basic for Applications (VBA) to create Auto-Germ, which is an Excel workbook that allows a user to estimate field germination timing based on wet-thermal accumulation models and field temperature and soil moisture data. To demonstrate the capabilities of Auto-Germ, we calculated various germination indices and modeled germination timing for 11 different species, across 6 years, and 10 Artemisia-steppe sites in the Great Basin of North America to identify the planting date required for 50% or more of the simulated population to germinate in spring (1 March or later), which is when conditions are predicted to be more conducive for plant establishment. Both between and within the species, germination models indicated that there was high temporal and spatial variability in the planting date required for spring germination to occur. However, some general trends were identified, with species falling roughly into three categories, where seeds could be planted on average in either fall (Artemisia tridentata ssp. wyomingensis and Leymus cinereus), early winter (Festuca idahoensis, Poa secunda, Elymus lanceolatus, Elymus elymoides, and Linum lewisii), or mid-winter (Achillea millefolium, Elymus wawawaiensis, and Pseudoroegneria spicata) and still not run the risk of germination during winter. These predictions made through Auto-Germ demonstrate that fall may not be an optimal time period for sowing seeds for most non-dormant species if the desired goal is to have seeds germinate in spring.

Plant attributes and their relationship to the germination response to different temperatures of 18 species from central Mexico

Germination responses of non-dormant seeds to temperature and thermal requirements are affected by the geoclimatic origin of the species, along with specific attributes such as life form, life cycle or seed size. We evaluated the relationship of these attributes and temperature to germination in 18 species that inhabit a convergence area of two biogeographic realms. Seeds were sown at different constant temperatures. Base temperature (T_b ) and thermal time for 50% germination (θ_T(50) ) were determined. For T_b , θ_T(50) and seed size, we performed a cluster analysis and then applied a discriminant analysis (DA). DA was also performed using geoclimatic origin, life form and life cycle as grouping variables. Seed that did not germinate were transferred to the benefit temperature for germination. Finally, ethylene was applied to the remaining seeds that did not germinate. Temperature significantly affected final germination. T_b varied between 5 and 13 °C in 15 species and 19.0-21.5 °C in the remainder; θ_T(50) was 7-30 °Cd in eight species and 50-109 °Cd in the remainder. Cluster analysis showed three groups, and DA evidenced the relevance of T_b and θ_T(50) for this separation. Differences in life cycle were related to θ_T(50) . The geoclimatic origin was not significant. Thermoinhibition or thermodormancy were found in some species. T_b overlaps with environmental temperature of the growth season. Thermal traits for germination mainly reflect the species' life cycle, which is related to the main differences in reproductive performance among annuals and perennials. Local adaptation might mask the effect of geoclimatic origin of a species.

[Seed morphology and effects of sheep rumen digestion on seed germination of 28 Gramineae plants.]

An experiment was undertaken to compare the morphological characteristics of seeds of 28 Gramineae plants which widely distributed in north Xinjiang and to study their digestion in the rumen of sheep. After determining their morphological characteristics including seed length, width, height, seed shape index, 100-seed mass, and seed germination percentage, seeds were put into nylon bags and then placed in the rumen of sheep through a fistula. The bags were removed at different times to determine the morphological characteristics and seed germination rates. The results showed that 23 plant seeds were all elliptic or flat types except for Melica scabrosa, Agrostis ma-tsumurae, Poa bulbosa, Phleum pratense and Triticum aestivum. 100-seed mass of T. aestivum (3.25 g) and Avena sativa (1.69 g) were >1 g, and the 100-seed mass of the other seeds ranged from 0.01-1 g, indicating they were all medium or small type seeds. The color of seed coat was deepened, seed structure was destructed, and the lengths of seed appendages, i.e., awn, lemma and glume were decreased with increasing digestion time. Seed length, width, height, 100-seed mass were decreased with increasing digestion time, but the changes were not significant compared with the non-digested seeds. The seed germination percentages were extremely decreased after sheep rumen digestion. After 6 h of sheep rumen digestion, the germination rates of the seeds of R. kamoji and A. sativa were decreased to 0, and part of the seeds of other 26 plants still had some vigor.

Akinetes May Be Representative of Past Nostocalean Blooms: a Case Study of Their Benthic Spatiotemporal Distribution and Potential for Germination in a Eutrophic Lake

Monitoring of water and surface sediment in a French eutrophic lake (Lake Aydat) was carried out over a 2-year period in order to determine whether akinetes in sediment could be representative of the most recent bloom and to estimate their germination potential. Sediment analysis revealed two akinete species, Dolichospermum macrosporum and Dolichospermumflos-aquae, present in the same proportions as observed for the pelagic populations. Moreover, similar spatial patterns observed for vegetative cells in the water column and akinete distributions in the sediment suggest that akinetes in the sediment may be representative of the previous bloom. However, the relationship between akinetes in the sediment and vegetative cells in the water column was not linear, and other factors may interfere. For example, our results highlighted horizontal transport of akinetes during the winter. The benthic overwinter phase did not seem to influence the percentages of intact akinetes, which remained stable at approximately 7% and 60% for D. macrosporum and D. flos-aquae, respectively. These percentages may thus be the result of processes that occurred in the water column. The intact overwintering akinetes showed germination rates of up to 90% after 72 h for D. flos-aquae or 144 h for D. macrosporum The difference in akinete germination rates between these two species demonstrates different ecological strategies, which serve to expand the window for germination in time and space and thus optimize colonization of the water column by nostocalean cyanobacteria.IMPORTANCE Cyanobacteria have the ability to proliferate and to form blooms. These blooms can then affect the local ecology, health, and economy. The akinete, a resistant cell type that persists in sediment, is an important intermediate phase between previous and future blooms. We monitored the water column and the surface sediment of a French eutrophic lake (Lake Aydat) to investigate the relationship between vegetative cells in the water column and akinetes in the sediment. This study focused on the characterization of spatiotemporal akinete distributions, cellular integrity, and germination potential. Species-specific ecological strategies were highlighted and may partly explain the temporal succession of species in the water column. Akinetes may also be used to understand past nostocalean blooms and to predict future ones.

Effect of corona discharge plasma jet on surface-borne microorganisms and sprouting of broccoli seeds

BACKGROUND

Different pathogenic microorganisms have been reported to cause sprouts-associated outbreaks. In order to sterilise and enhance the germination of seeds, non-thermal plasma has been increasingly investigated in the field of agricultural science as an alternative to the traditional pre-sowing seed treatments. This work aimed to evaluate the effect of corona discharge plasma jet (CDPJ) on disinfection of the natural bio-contaminants of broccoli seed and also studied the plasma effect on sprout seed germination rate and physico-chemical properties of sprouts.

RESULTS

Aerobic bacteria, moulds and yeasts, B. cereus, E. coli, Salmonella spp. were detected on the broccoli seed surface. After 0-3 min treatment using CDPJ, the detected microorganisms were reduced in the range of 1.2-2.3 log units. Inactivation patterns were better explained using pseudo-first-order kinetics. The plasma treatment of seeds up to 2 min exhibited a positive effect on germination rate, seedling growth. The physico-chemical and sensory characteristics of sprouts were unaffected due to the CDPJ treatment of their respective seeds.

CONCLUSION

Corona discharge plasma jet can potentially be used for microbial decontamination of broccoli seeds. In addition, the plasma treatment of broccoli sprout seeds has enabled a significant enhancement in their germination rate and seedling growth without compromising physico-chemical and sensory characteristics of their corresponding sprouts. © 2016 Society of Chemical Industry.

Autotoxicity and allelopathy of 3,4-dihydroxyacetophenone isolated from Picea schrenkiana needles

Bioassay-guided fractionation of the diethyl ether fraction of a water extract of Picea schrenkiana needles led to the isolation of the phenolic compound 3,4-dihydroxy- acetophenone (DHAP). The allelopathic effects of DHAP were evaluated under laboratory conditions on P. schrenkiana, rice (Oryza sativa L.), wheat (Triticum aestivum L.), radish (Raphanus sativus L.), lettuce (Latuca sativa L.), cucumber (Cucumis sativus L.) and mung bean (Phaseolus radiatus L.). DHAP significantly inhibited seed germination and seedling growth of P. schrenkiana at concentrations of 2.5 mM and 0.5 mM (p < 0.05). Soil analysis revealed that P. schrenkiana forest soils contained exceptionally high DHAP concentrations (mean = 0.51 ± 0.03 mg/g dry soil), sufficient to inhibit natural P. schrenkiana recruitment. DHAP also exhibited strong allelopathic potential. It significantly inhibited wheat and lettuce seed germination at concentrations of 1 mM and 0.5 mM (p < 0.05). The active compound also completely inhibited root growth of the six test species at high concentrations. Our results suggest a dual role of DHAP, both as an allelochemical and as an autotoxicant. The potential for a single plant needle-leached compound to influence both inter- and intra-specific interactions emphasized the complex effects that plant secondary metabolites might have on plant population and community structure.

Kinship between parents reduces offspring fitness in a natural population of Rhododendron brachycarpum

BACKGROUND AND AIMS

A reduction in offspring fitness resulting from mating between neighbours is interpreted as biparental inbreeding depression. However, little is known about the relationship between the parents' genetic relatedness and biparental inbreeding depression in their progeny in natural populations. This study assesses the effect of kinship between parents on the fitness of their progeny and the extent of spatial genetic structure in a natural population of Rhododendron brachycarpum.

METHODS

Kinship coefficients between 11,858 pairs of plants among a natural population of 154 R. brachycarpum plants were estimated a priori using six microsatellite markers. Plants were genotyped, and pairs were selected from among 60 plants to vary the kinship from full-sib to unrelated. After a hand-pollination experiment among the 60 plants, offspring fitness was measured at the stages of seed maturation (i.e. ripening) under natural conditions, and seed germination and seedling survival under greenhouse conditions. In addition, spatial autocorrelation was used to assess the population's genetic structure.

KEY RESULTS

Offspring fitness decreased significantly with increasing kinship between parents. However, the magnitude and timing of this effect differed among the life-cycle stages. Measures of inbreeding depression were 0.891 at seed maturation, 0.122 (but not significant) at seed germination and 0.506 at seedling survival. The local population spatial structure was significant, and the physical distance between parents mediated the level of inbreeding between them.

CONCLUSIONS

The level of inbreeding between individuals determines offspring fitness in R. brachycarpum, especially during seed maturation. Genetic relatedness between parents caused inbreeding depression in their progeny. Therefore, biparental inbreeding contributes little to reproduction and instead acts as a selection force that promotes outcrossing, as offspring of more distant (less related) parents survive better.

Dormancy and germination characteristics of herbaceous species in the seasonally dry tropics of northern Australia

This study investigated changes in dormancy and germination over 8 months for 23 common species (annual and perennial grasses, legumes and other dicotyledons) from herbaceous communities in northern Australia. Seeds were exposed to three storage treatments: relatively constant laboratory conditions, an oven with fluctuating temperatures similar to those found on the soil surface (25/60°C), or exposed on the soil surface at Townsville. There were wide ranges of initial levels of dormancy (9–100%), rates of change of dormancy and response to the different storage conditions showing that species with several types of dormancy characteristics are able to coexist in these communities. The general trend in dormancy levels was a decline with time with the rate of decline greatest for seeds exposed on the soil surface and least for those stored in the laboratory. The species were divided into groups based on dormancy levels in seeds on the soil surface during the late dry and mid wet seasons. The dormancy characteristics of the groups were related to the ecology of the species in the groups. There was an approximately linear increase in germination rate (i.e. a decrease in the number of days to 50% of final germination) over time for all storage treatments; rates for seeds on the soil surface increased more rapidly than those of seeds in laboratory and oven samples.