Seed Dormancy Research Articles

Seed coat colour and structure are related to the seed dormancy and overwintering ability of crop-to-wild hybrid soybean

Abstract The possible persistence of genetically modified (GM) crop-to-wild hybrid seeds in the soil seed bank is a major concern in risk assessment and is closely related to seed characteristics such as dormancy. In the present study, we generated F3 hybrids via crosses between GM soybean accessions and wild soybean and evaluated the dormancy, overwintering ability and inheritance of foreign genes in different-coloured hybrid seeds (yellow, green, brown and black). The results revealed that the 5-enolpyruvylshikimate-3-phosphate synthase transgene may have no influence on crop wild hybrid seed dormancy and overwintering ability, and the dormancy of the hybrid seeds was closely related to seed coat colour. F3 hybrid seeds with light colours (yellow and green) were relatively nondormant, while seeds that were dark (brown and black) in colour were relatively dormant. Moreover, the hybrid seeds that were dark in colour had a much stronger overwintering ability than the lighter-coloured seeds, with 21.33 % of the black seeds and 33.33 % of the brown seeds remaining viable after 240 days of soil burial. In contrast, almost all the F3 yellow and green seeds were no longer viable during winter. Scanning electron microscopy revealed that the lighter-coloured seeds had a thin palisade layer and very few surface deposits, while the darker-coloured seeds had a thicker palisade layer and a large area of honeycomb-like surface deposits similar to those of wild soybean seeds. Thus, the physical dormancy and overwintering ability of the darker-coloured seeds may be related to the seed coat. Our results suggest that transgenes of GM soybean might disperse into wild populations and persist in seed banks.

Effect of fire on weed dynamics and behavior of pre-emergent herbicides in Eucalyptus spp. plantations

The forest fires that occurred during summer 2021-22 in Uruguay generated concern in several areas, including silvicultural systems. The fire could generate changes at the flora level by changes in the dormancy of soil bank seeds, and in the behavior of frequently used pre-emergent herbicides due to inactivation by ashes. These possible changes impose a challenge in connection to weed control. In this study, an attempt was made to provide an answer to the problem by evaluating the dynamics of weeds and the behavior of pre-emergent herbicides in post-fire Eucalyptus plantations. The evaluations were carried out in two sites previously burned —one of them previously harvested and the other one not, being able to obtain data in different conditions. The weed dynamics was evaluated through the observational study of the percentage of total weed cover and present species were identified. With the data obtained, the parameters frequency, diversity and richness were calculated to analyze the different properties separately. Pre-emergent herbicides were evaluated in a randomized block experimental design: S-metolachlor, flumioxazin + S-metolachlor , isoxaflutole + S-metolachlor, oxifluorfen + S-metolachlor . Proposed treatments were assessed for possible interactions with fire and removal of the first cm of soil and ashes. Weed density was evaluated by characterizing and quantifying how many weeds could emerge in a square 30cm×30cm. While one of the fields was evaluated 8, 23, 31, 41, 61, and 82 days post application (DPA), the other was evaluated 8, 20, 31, 41, and 61 DPA. On both experiments the fire showed an increase in the weeds. In one experiment the weeding percentage increment was 64.9% on the burned area, while on the other it was 54.3 %. In addition, in the non-harvested field there were no large amounts of weeds on both treatments due to the conditions that standing trees generated. The results of weed control did not show interaction between efficiency and ashes presence, and were related to the species present in the weed bank, not showing a clear trend among the herbicide treatments. The S-metolachlor treatment was always the highest in number of weeds. The number of weed|m2 was about 17-25 on the harvested field, and 3-4 weed|m2 on the non-harvested one. The fire generated changes in the expression at seed bank of soil. This study was an important development in the generation of knowledge for future production.

Histogenesis and reserve dynamics during the maintenance of dormancy and germination in seeds of the basal palm Mauritiella armata.

The germination and post-seminal development of Arecaceae are notably complex due to the microscopic dimensions of the embryonic axis, the occurrence of dormancy, and the diversity of reserve compounds. In-depth information on this subject is still limited, especially in terms of the basal sub-family Calamoideae. Mauritiella armata is widely distributed in the Amazon region and is considered a key species in flooded ecosystems (veredas) in the Cerrado biome. We sought to describe histogenesis and reserve compound dynamics during the germination of M. armata, as well as the changes in incubated seeds over time. Seeds with their operculum removed (the structure that limits embryonic growth) were evaluated during germination using standard methods of histology, histochemistry, and electron microscopy. Evaluations were also performed on intact seeds incubated for 180 days. The embryos show characteristics associated with recalcitrant seeds of Arecaceae: a high water content (>80%), differentiated vessel elements, and reduced lipid reserves. Both the embryo and endosperm store abundant reserves of proteins, neutral carbohydrates, and pectins. The completion of germination involves cell divisions and expansions in specific regions of the embryo, in addition to the mobilization of embryonic and endospermic reserves through symplastic and apoplastic flows. Intact seeds show dormancy (not germinating for 180 days), but exhibit continuous development associated with cell growth, differentiation, and reserve mobilization. The anatomical and histochemical characters of M. armata seeds indicate an association between recalcitrance and dormancy related to the species' adaptation to flooded environments.

Overcoming Tegumentary Numbness in Seeds of Crotalaria spectabilis and Crotalaria paulinea

Objective: To evaluate the efficiency of dormancy breaking methods in seeds of C. paulinea and C. Spectabilis. Theoretical reference: Species of crotalaria, such as C. paulinea and C. spectabilis, found in the Brazilian territory, are used as green manure in large crops and vegetable productions. However, the presence of tegumentary hardness in their seeds can result in failures in soil cover, which favor the emergence of weeds. Method/design/approach: The research was carried out at the Laboratório de Análise de Sementes of the Departamento de Agronomia, at the Universidade Federal de Viçosa, Minas Gerais. Twenty treatments were applied to the seeds to break dormancy, using mechanical scarification with 120 grit sandpaper, hot water in an oven at 90 °C for five and seven minutes, and immersion in sodium hypochlorite at four concentrations, 2%, 4%, 6% and 8%, for four times, two, four, six and eight hours. Results and conclusion: The most efficient treatments for breaking this dormancy in both species of crotalaria were scarification with sandpaper and immersion in water at 90±3 °C for seven minutes. Treatments using sodium hypochlorite were not effective in reducing the number of hard seeds. Originality/value: Feasibility of the methods applied to break dormancy in seeds of C. paulinea and C. Spectabilis, since they are used for green manure, and control of Aedes aegypti, among other purposes.

Characterization of Brazilian black oat genotypes regarding seed dormancy

The objective of this work was to characterize 30 black oat genotypes regarding seed dormancy. The experiment was carried out in the 2018 and 2019 seasons in a completely randomized design with three factors, being 30 black oat genotypes, two methods of seed germination analysis (with and without dormancy breaking) and five evaluation periods (0, 30, 60, 90 and 120 days after harvest), distributed in four replicates. In each postharvest period, the variables: normal seedlings, abnormal seedlings, number of dormant seeds and number of dead seeds were analyzed. There was significant interaction between factors during the two years of experimentation. In the 2018 season, the percentage of dormant seeds at period zero ranged from 47 to 3% in the method with overcoming dormancy, 86 to 33% in the method without overcoming dormancy. The genotypes ALPHA 1629 and IAPAR 61- Ibiporã presented highest dormancy. In the 2019 season, the percentage of dormant seeds at period zero ranged from 56 to 3% with overcoming dormancy and 85 to 12% without overcoming dormancy. There is variability of dormancy among genotypes and this is overcome after 60 days of harvest. The IAPAR 61-Ibiporã genotype have highest of dormancy seeds.

Fruit dehiscence mechanism and release of dimorphic seeds with different germination properties in Commelina erecta.

Commelina erecta is a successful weed species. The aims of this study were to analyse the morpho-anatomy of the fruit and dimorphic seeds of the weed C. erecta, the dynamics and type of dormancy, and water entry. Flowers and fruits at different development stages were processed using standard anatomical techniques. Besides, experiments of imbibition, germinability and water entry were performed on both seed types. In the fruit of C. erecta, free and coated seeds are developed within dehiscent and indehiscent carpels, respectively. Dehiscent carpels open through a region of mechanical weakness in the dorsal vascular bundle. This region does not form in the indehiscent carpel. The main anatomical differences between the two seed types were observed in the testa and in the number of covering layers. Imbibition experiments showed that the covering of both seed types is water permeable, so these seeds lack physical dormancy and may exhibit physiological dormancy. Germinability experiments showed that the dormancy in free seeds is variable throughout the reproductive season, whereas, in coated seeds, it is high throughout the reproductive season. The embryotega is an area where the hardness of the seed coat is interrupted and facilitates water entry. Differences in the morpho-anatomy of carpels result in the formation of dimorphic seeds with different covering layers and different germination properties. These different properties allow some seeds germinate immediately after falling from the mother plant, and others to be incorporated into the seed bank. These results are useful for designing weed management strategies in agroecosystems.

Biological Flora of Britain and Ireland:Geranium pratense

AbstractThis account presents information on all aspects of the biology ofGeranium pratenseL. (Meadow Crane's‐Bill). The main topics are presented within the standard framework of theBiological Flora of Britain and Ireland: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation.Geranium pratenseis a perennial gynodioecious forb of neutral grassland. In Britain and Ireland, it is particularly abundant on roadside verges, railway embankments, the margins of watercourses and woodland rides. It is generally intolerant of grazing and is absent or scarce in livestock‐grazed grassland.Geranium pratenseis widespread in England, Wales and Scotland but is scarce in Ireland. It has an extensive native range in Europe and Asia, extending eastwards to Russia, north‐western China and Mongolia. It has been widely introduced to new sites within its native range and has been introduced to Canada, the USA and New Zealand.Geranium pratenseusually occurs on free‐draining soils but also infrequently where drainage is impeded. The soils are often nutrient‐rich and weakly acidic to weakly alkaline. The underlying geology is usually non‐acidic sedimentary rocks or superficial deposits.Geranium pratenseis protandrous and is pollinated by various insects of the orders Hymenoptera, Diptera and Lepidoptera, particularly bumblebees, solitary bees, hoverflies and butterflies. Eleven species of phytophagous insect have been recorded onG. pratensein Britain and Ireland.Geranium pratensehas little or no capacity for vegetative spread. Primary seed dispersal is ballistic and seeds may be flung over distances of up to several metres. The species has a transient seed bank, that is germination typically takes place in the winter and spring after seed production, after the physically dormant seeds have become permeable. Seedling establishment is higher in vegetation‐free gaps than in undisturbed grassland vegetation.There has been no significant change in its distribution between the late 1950s and 2019, although since 2000, it has expanded its range, mainly via introductions, in northern and western Scotland, west Wales and in Ireland. Alien sites have increased markedly since the 1960s due to introductions from wildflower seed sowing and spread from gardens.

Dormancy-break and germination requirements for seeds of the threatened Austral papaya (Carica chilensis)

Seed dormancy is one of the most important adaptive mechanisms in plants, optimizing germination, seedling emergence, and establishment to ensure these processes occur when environmental conditions are favorable for plant survival and growth. Endemic to rocky environments of the southern Atacama Desert, the Austral papaya (Carica chilensis) is the papaya species with the southernmost distribution within the Caricaceae, thriving in the most extreme environmental conditions. This threatened plant exhibits low natural regeneration, primarily attributed to low germination, yet no information regarding seed dormancy release is available. In this study, we investigated the dormancy-break and germination requirements of C. chilensis. We hypothesized that if C. chilensis seeds exhibit physiological dormancy, then seeds with reduced moisture content and those treated with chemicals or growth hormones would exhibit higher germination percentages and faster germination than control seeds akin to other members of Caricacea. Our results confirmed this prediction and revealed that ultra-drying (< 3% moisture content) and treating seeds with sulfuric acid, gibberellic acid, or potassium nitrate are the most effective methods for germinating C. chilensis. Consequently, we suggest using these treatments to propagate this threatened papaya species.

OsNAC2 regulates seed dormancy and germination in rice by inhibiting ABA catabolism

Seed dormancy and germination determine the beginning of the life cycle of plants, and the phytohormone ABA plays a crucial role in regulation of seed dormancy and germination. However, the upstream regulatory mechanism of ABA metabolism during dormancy releasing is still remain elusive. In this paper, we present a novel mechanism of OsNAC2 in controlling ABA metabolism and regulation of seed dormancy. OsNAC2 highly expressed during seed development and germination, and overexpression of OsNAC2 strengthened seed dormancy and suppressed germination. Moreover, exogenous phytohormone treatment showed that OsNAC2 acted upstream of GA signaling and downstream of ABA signaling. Additionally, overexpression of OsNAC2 inhibited ABA degradation and increased ABA content during early germination. Further molecular analysis revealed that OsNAC2 directly bound to the ABA metabolism genes promoter and inhibits their transcription in rice protoplasts. These finding could help us explain the genetic regulation mechanism of ABA metabolism during dormancy release and germination in rice.

Overcoming seed dormancy of Taxus baccata L. by embryo rescue leads to germination and seedling growth

Hairy roots generated by Rhizobium rhizogenes-mediated transformation of yew (Taxus spp.) is a promising approach to enhance production of Taxol® (paclitaxel), which is one of the most effective anticancer drugs. As a prerequisite, it is pivotal to successfully produce Taxus seedlings for transformation. However, the deep dormancy of Taxus seeds leads to extreme difficulties in seed germination. Therefore, embryo rescue has been used to break the dormancy of Taxus baccata seeds, thereby producing seedlings for transformation. In the current study, a successful strategy of embryo rescue was to sterilize the surface of T. baccata seeds collected from the field at two different maturity stages (low and high). The strategy resulted in 100% germination rate, but it was worth noting that not all germinated embryos grew into fully developed plants. As a result, the present experiment introduced an innovative indicator—fully developed seedling index—to describe the growth of seedlings developed by germinated embryos. Collectively, the data revealed that 21 ± 4% of the seedlings eventually grew into fully developed plants. Regarding the development of the seedlings, the fully developed seedling index increased initially along with seedling growth, reaching a peak after 2 weeks. Subsequently, the fully developed seedling index from low maturity seeds and high maturity seeds began to decrease until it stabilized after 4 weeks and 7 weeks, respectively. Consequently, the new findings proved helpful to select T. baccata seeds with appropriate maturity, hence developing a reliable technique to produce viable seedlings for a transformation pipeline.

Microclimate and seed bank under Pithecellobium keyense (Fabaceae) in a coastal scrubland

AbstractMicroclimatic conditions affect seeds' survival, dormancy, and germination, which are determinants in vegetation succession and recovery. The semiarid coastal scrublands of Yucatan, Mexico are very important because of the environmental services they provide thus, studies are needed in disturbed sites in relation to seed viability and microclimate. In this study, we characterized the microclimate and seed bank under Pithecellobium keyense shrubs, during the rainy and dry seasons. We collected soil samples and measured microenvironmental variables under adult P. keyense at three different positions under the canopy of every studied individual (“open” or completely sunny, “half‐shaded,” placed at the border of the canopy, and “fully shaded” placed under the canopy, next to the stem of the shrub). Photosynthetic photon flux density (PPFD), minimum night‐time temperature, and maximum daytime temperature behaved differently among positions under the canopy both in rainy and dry seasons. During the rainy season, seed viability was no different among microenvironments, while in the dry, the highest was found in the fully shaded and the lowest in the open position. Microclimatic variables under the canopy of P. keyense had an effect on the probability of seed viability in Chuburná; and this effect was stronger in the dry season.Abstract in Spanish is available with online material.

Effects of Pre-Treatments on Seed Dormancy and Germination of Endemic Muscari bourgaei Baker

M. bourgaei Baker is an endemic plant that grows in Türkiye. It has the potential to be an ornamental plant, so it is important to know its germination characteristics and seed morphological characteristics. We evaluated the effects of moist chilling (3 to 12 months) and application of gibberellic acid (GA3) (250 to 1000 mg/L−1) on seed germination under two different light regimes (light phase and dark phase) and four temperature regimes (20, 20/10, 25/15, and 15/10 °C). Seeds were collected from the subalpine belt of Mount Uludağ at an altitude between 2200 and 2300 m. M. bourgaei seeds were dormant and reached the highest germination percentage after 12 months of moist chilling. GA3 applications only have a limited effect on the breaking of dormancy in most cases. Maximum germination of 28 percent was obtained by the GA3 application of 1000 mg/L under dark phase with incubation at 15/10 °C. Scarification with sulfuric acid did not result in any germination. Seed germination of above 80 percent was obtained after 6 months of moist chilling and above 90 percent after 9 and 12 months of moist chilling. Intermediate physiological dormancy was determined as the type of dormancy. Our findings on seed germination and dormancy characteristics of M. bourgaei, which is an endemic alpine meadow plant, will contribute to the protection and development of the germplasm of this species.

A long-term experiment reveals no trade-off between seed persistence and seedling emergence.

Information on seed persistence and seedling emergence from the soil seed bank is critical for understanding species coexistence and predicting community dynamics. However, quantifying seed persistence in the soil is challenging; thus, its association with other life-history traits is poorly known on a broad scale. Using germination phenology for 349 species in a 42-yr experiment, we quantified the persistence-emergence correlations and their associations with intrinsic regeneration traits using Bayesian phylogenetic multilevel models. We showed no trade-off between seed persistence and seedling emergence. Physically dormant seeds were more persistent but exhibited lower emergence than nondormant seeds. Monocarpic species had both higher persistence and emergence than polycarpic species. Seed mass posed a marginal proxy for persistence, while emergence almost doubled from the smallest to the largest seeds. This study challenges the traditional assumption and is the first demonstration of noncorrelation between persistence and emergence, probably owing to the complexity of regenerative strategies. Species with short persistence and low emergence would be the most vulnerable for insitu conservation. Our analyses of this unique, long-term dataset provide a strong incentive for further experimental studies and a rich data resource for future syntheses.

Tratamentos pré-germinativos no controle da dormência de sementes de Myracrodruon urundeuva fr. All (aroeira-preta)

The objective of this work was to test different methods to overcome dormancy in seeds of Myracrodruon urundeuva, a species of economic and environmental interest. Seven treatments were tested, plus the control. The parameters analyzed were the percentage and speed of germination and the statistical analysis adopted the completely randomized design and the Tukey test (5%). Conclusions: 1) chemical scarification compared to mechanical scarification is a good option to speed up seed germination; 2) seed immersion was not interesting in breaking dormancy and 3) sulfuric acid and washing in running water (2 hs), for germination speed, are statistically superior to the control.

Dormancy Behaviour and Effectiveness of Dormancy Breaking Methods in Cucumber Seeds (Cucumis Sativus)

This study aimed to examine the dormancy behaviour and effectiveness of various dormancy breaking treatments on cucumber seeds. Freshly harvested cucumber seeds of varieties CU-1047 and CU-1051 were extracted, dried and stored for eight weeks at ambient temperature. The stored seed lots were tested for seed germination once a week and hormone analysis (ABA, GA, zeatin and kinetin) every two weeks. In a second experiment, dormancy breaking methods using dry heat treatment (DHT) at 36, 50 or 80°C for various lengths of time. Chemical treatments were also tested, with a 24-hour soaking time using GA3, KNO3 or ultra-fine bubble (UFB) water. The results showed that the dormancy persistence in both varieties was three weeks after the seeds were harvested, by which time germination reached more than 85%. The decrease in ABA content during the storage period correlated with an increase in seed germination. The most effective methods of breaking dormancy were dry heat at 80°C for 24 hours (highest germination: 62%) and a DHT chamber (59%) compared with control (1%). An alternative method was soaking the seeds in 1% KNO3 followed by drying to the initial moisture content (55% germination). UFB water was not effective in breaking the dormancy of cucumber seeds.

Premetastatic Niche Mimicking Bone-On-A-Chip: A Microfluidic Platform to Study Bone Metastasis in Cancer Patients.

Primary cancer modulates the bone microenvironment to sow the seeds of dormancy and metastasis in tumor cells, leading to multiple organ metastasis and death. In this study, 3D printing and bone-on-a-chip (BOC) are combined to develop a BOC platform that mimics the pre-metastatic niches (PMNs) and facilitates elucidation of the interactions between bone-resident cells and metastatic tumor cells under the influence of primary cancer. Photocrosslinkable gelatin methacrylate (GelMA) is used as a 3D culturing hydrogel to encapsulate cells, and circulate tumor culture medium (CM) adjacent to the hydrogel to verify the critical role of mesenchymal stem cells (MSCs) and osteoclasts (RAW264.7s). Three niches: the dormancy niche, the perivascular niche, and the "vicious cycle" niche, are devised to recapitulate bone metastasis in one chip with high cell viability and excellent nutrient exchange. With respect to tumor dormancy and reactivation, the invadopodia formation of A549 lung cancer cells in communication with MSCs and RAW264.7 via the cortactin pathway is researched. As a proof of concept, the functionality and practicality of the platform are demonstrated by analyzing the invadopodia formation and the influence of various cells, and theestablishment of the dynamic niches paves the way to understanding PMN formation and related drug discovery.

RICE SEED TREATMENTS BY SOAKING IN WATER AND THREE PESTICIDES (CARBOSULFAN, BENOMYL, AND IMIDACLOPRID) TO CONTROL FOLIAR NEMATODE Aphelenchoides besseyi

Aphelenchoides besseyi is one of the most important parasitic nematodes in rice plants, capable of dormancy in rice seeds. This study aims to determine the effects of soaking rice seeds in water and pesticides (carbosulfan, benomyl, and imidacloprid) on the mortality of A. besseyi, seed viability, and symptoms in rice seedlings. This study specifically used rice seeds infected with A. besseyi. Cold water treatment (cwt) at 5-10˚C for 24 hours followed by hot water treatment (hwt) at 52˚C for 10 minutes caused 51.17% A. besseyi mortality yet reduced the seed viability. Soaking the seed in the water at 25-30˚C for 24 hours followed by hwt at 57˚C for 10 minutes and hwt at 52˚C for 10 minutes could cause 48.67%, 39.18% and 33.05% nematode mortality, respectively. Low nematode mortality in all treatments (less than 60%) showed symptoms of A. besseyi infection in rice seedlings 21 days after planting. Seed dressing with imidacloprid 5WP (2% by seed weight) caused 47.25% A. besseyi mortality, whereas benomyl 50WP (0.2% by seed weight) and carbosulfan 25ST (2% by seed weight) caused only 27.61% and 11.34%. Based on two parameters (nematode mortality and seed viability), the most effective treatments were soaking the rice seeds in the water at 25-30˚C for 24 hours and seed dressing with imidacloprid.

Impact of Hydrochloric acid on breaking seed dormancy and germination enhancement in native Alhagi graecorum Boiss ( Al-Agool ).

Despite the great importance of legumes plants, most of them have a hard and impermeable testa, which causes physical dormancy of the seeds and prevents germination even when environmental conditions are favorable. This is considered one of the major problems in successful seed germination. Alhagi graecorum plant is a wild native legume. It has a hard and impermeable testa, which causes physical dormancy of seeds, and to overcome hard coat imposed dormancy, softening the hard seed coat by soaking Hydrochloric acid ( HCl ). The present study was conducted to evaluate various duration of soaking seeds in HCL to breaking physical dormancy for A.graecorum in 10, 20, and 30 minutes. The results showed that, final germination percentage (FGP) in treated seeds significantly increased when compared with the control were 55, 62 and 68 % respectively, while in control was only 12 %. Seed germination influenced by HCL is due to its capability to break the hard seed coat that leads to water absorption and imbibition of seeds. As for the mean daily germination ( MDG ), the results revealed that, there were significance increased in seventh day of sowing in germination between the treated seeds in duration of soaking 20 and 30 min were 23 and 24 % respectively, as they were most effective in germination, while the germination in the control stopped in the fifth day of sowing at 12 %. While the mean germination time (MGT), the results indicated that the seeds soaked in acid recorded 9.66, 9.13, and 8.62 days, respectively. The minimum MGT for treated seeds was detected in 30 min., 8.62 days. The reason for the long period of the mean germination time may be due to the use of a low concentration of hydrochloric acid, so I recommend using higher concentrations of acid to obtain a lower mean germination time.

Global seed dormancy patterns are driven by macroclimate but not fire regime.

Seed dormancy maximizes plant recruitment in habitats with variation in environmental suitability for seedling establishment. Yet, we still lack a comprehensive synthesis of the macroecological drivers of nondormancy and the different classes of seed dormancy: physiological dormancy, morphophysiological dormancy and physical dormancy. We examined current geographic patterns and environmental correlates of global seed dormancy variation. Combining the most updated data set on seed dormancy classes for > 10 000 species with > 4 million georeferenced species occurrences covering all of the world's biomes, we test how this distribution is driven by climate and fire regime. Seed dormancy is prevalent in seasonally cold and dry climates. Physiological dormancy occurs in relatively dry climates with high temperature seasonality (e.g. temperate grasslands). Morphophysiological dormancy is more common in forest-dominated, cold biomes with comparatively high and evenly distributed precipitation. Physical dormancy is associated with dry climates with strong seasonal temperature and precipitation fluctuations (e.g. deserts and savannas). Nondormancy is associated with stable, warm and wetter climates (e.g. tropical rain forest). Pyroclimate had no significant effect on the distribution of seed dormancy. The environmental drivers considered in this study had a comparatively low predictive power, suggesting that macroclimate is just one of several global drivers of seed dormancy.

WEAK SEED DORMANCY 1, an aminotransferase protein, regulates seed dormancy in rice through the GA and ABA pathways

Seed dormancy is a critical trait that enhances plant survival by preventing seed germination at the wrong time or under unsuitable conditions. Lack of seed dormancy in rice can lead to pre-harvest sprouting on mother plants leading to reduced yield and seed quality. Although some genes have been identified, knowledge of regulation of seed dormancy is limited. Here, we characterized a weak seed dormancy mutant named weak seed dormancy 1 (wsd1) that showed a higher seed germination percentage than the wild-type following the harvest ripeness. We cloned the WSD1 encoding an aminotransferase protein using a MutMap approach. WSD1 was stably expressed after imbibition and its protein was localized in the endoplasm reticulum. A widely targeted metabolomics assay and amino acid analysis showed that WSD1 had a role in regulating homeostasis of amino acids. PAC treatment and RNA-seq analysis showed that WSD1 regulates seed dormancy by involvement in the GA biosynthesis pathway. GA1 content and expression of GA biosynthesis-related genes were increased in the wsd1 mutant compared with the wild-type. The wsd1 mutant had reduced sensitivity to ABA. Our overall results indicated that WSD1 regulates seed dormancy by balancing the ABA and GA pathways.