Glucose-induced inhibition of seed germination in Lotus japonicus is alleviated by nitric oxide and spermine

Seed germination is sensitive to glucose (Glc), nitric oxide (NO) and polyamine (PA). To elucidate whether cross-talk among Glc, NO and PAs occurs in mediation of seed germination, effects of Glc, NO and spermine on seed germination of Lotus japonicus were studied. Glc retarded seed germination in a concentration-dependent manner. NO donor sodium nitroprusside (SNP) alleviated Glc-induced inhibition of seed germination, whereas the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (cPTIO) diminished the SNP-dependent alleviation of seed germination. These observations indicate that Glc may inhibit seed germination by interacting with NO signaling pathways. Exogenous spermine enhanced and the inhibitor of the spermine synthase, methylglyoxal-bis-guanyl hydrazone (MGBG), inhibited seed germination, respectively. Like SNP, spermine alleviated the Glc-induced inhibition of seed germination, whereas MGBG exaggerated the Glc-induced inhibition of seed germination. These results suggest that Glc may inhibit the spermine synthesis, leading to reductions in seed germination. NO scavenger and spermine synthase inhibitor diminished the SNP-induced alleviation of Glc-induced inhibition of seed germination. These findings reveal that both NO and spermine participate in the Glc-induced inhibition of seed germination in L. japonicus.     

Only seed size matters for germination in different populations of the dimorphic Tragopogon pratensis subsp. pratensis (Asteraceae)

Many studies have focused on the ecology of seed dimorphism, the production of two seed types by a single plant. Morphology and seed size are usually correlated, but how morphology affects germination percentage and seedling growth is poorly understood. Here we explicitly separate these effects for nine populations of the dimorphic species Tragopogon pratensis subsp. pratensis. Larger seeds yielded higher germination percentages, yet seed morphology had no additional direct effect on germination. Neither seed size nor seed morphology affected seedling growth. Neither germination nor seedling growth varied among populations, but seed head varied significantly. Results show that germination is mainly controlled by seed size rather than by seed morphology. This study is one of the few to distinguish explicitly between seed size and seed morphology effects on ecological characteristics and suggests that seed dimorphism may exert its ecological effects predominantly through its correlated size.     

Seed germination of GA-insensitive sleepy1 mutants does not require RGL2 protein disappearance in Arabidopsis

We explore the roles of gibberellin (GA) signaling genes SLEEPY1 (SLY1) and RGA-LIKE2 (RGL2) in regulation of seed germination in Arabidopsis thaliana, a plant in which the hormone GA is required for seed germination. Seed germination failure in the GA biosynthesis mutant ga1-3 is rescued by GA and by mutations in the DELLA gene RGL2, suggesting that RGL2 represses seed germination. RGL2 protein disappears before wild-type seed germination, consistent with the model that GA stimulates germination by causing the SCF(SLY1) E3 ubiquitin ligase complex to trigger ubiquitination and destruction of RGL2. Unlike ga1-3, the GA-insensitive sly1 mutants show variable seed dormancy. Seed lots with high seed dormancy after-ripened slowly, with stronger alleles requiring more time. We expected that if RGL2 negatively controls seed germination, sly1 mutant seeds that germinate well should accumulate lower RGL2 levels than those failing to germinate. Surprisingly, RGL2 accumulated at high levels even in after-ripened sly1 mutant seeds with 100% germination, suggesting that RGL2 disappearance is not a prerequisite for seed germination in the sly1 background. Without GA, several GA-induced genes show increased accumulation in sly1 seeds compared with ga1-3. It is possible that the RGL2 repressor of seed germination is inactivated by after-ripening of sly1 mutant seeds.     

濒危植物毛柄小勾儿茶种子休眠与萌发生理的初步研究

毛柄小勾儿茶（Berchemiella wilsonii （Schneid．）Nakai var．pubipetiolata H．Qian）为中国特有种,国家三级保护植物。TTC染色法测得毛柄小勾儿茶种子的生活力较低,仅为32％,空粒和无生活力的种子分别为28％和40％,说明毛柄小勾儿茶发育完全的种子较少。种子吸水速度试验证明毛柄小勾儿茶种皮透水性较差,不利于种子萌发时对水分的吸收,发芽抑制物的生物鉴定结果表明,毛柄小勾儿茶种子的不同部位都存在发芽抑制物,且种胚中的含量最高,不利于种子的萌发,使毛柄小勾儿茶种子处于休眠状态之中。几种不同浓度GA。溶液浸种24h的预处理可以不同程度地提高毛柄小勾儿茶种子的发芽率和发芽指数,其中300mg／L GA3的效果最显著,并且300mg／L GA3的预处理可以在萌发初期（萌发前3天）显著地提高毛柄小勾儿茶种子中过氧化物酶、过氧化氢酶和脱氢酶的活性。毛柄小勾儿茶种子生活力低,且处于休眠状态,再加上与种子发芽力有关的几种酶的活性较低,致使毛柄小勾儿茶种子的发芽率较低,同时这些也是从种子萌发生理方面导致毛柄小勾儿茶濒危的重要原因。     

曼陀罗种子休眠机理与破眠方法研究

通过对曼陀罗种子生活力测定、发芽试验、吸水率测定及种子萌发抑制物研究,揭示曼陀罗种子休眠机理,并利用物理、化学法处理曼陀罗种子,以探寻打破曼陀罗种子休眠的最佳方法.结果表明:(1)新采收的曼陀罗种子为综合休眠,休眠原因包括:种皮障碍、缺少萌发所需激素以及种皮和种仁中存在萌发抑制物,其中种皮障碍是限制种子萌发的首要因素.(2)室温存储6个月可解除曼陀罗种子种仁的休眠,但种皮障碍始终是其种子萌发的限制因素.(3)机械摩擦、浓H2SO4处理和NaOH处理均可打破除曼陀罗种皮的休眠障碍,促进种子萌发,其中用10% NaOH处理90 min为破除曼陀罗种皮休眠障碍的最佳方法,且发芽率比对照提高了83%.     

Does seed ingestion by bats enhance germination? A new meta‐analysis 15 years later

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植冠与土壤种子库储存种子的萌发特性及策略

为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度,选择研究区7种具有种子库的主要物种为研究对象,以刚成熟和室内储存种子为对照,比较植冠宿存(5个宿存期)和土壤埋藏(5a埋藏期)对植物种子萌发特性的影响,探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明:7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异,黄刺玫(Rosa xanthina)和水栒子(Cotoneaster multiflorus)种子萌发力表现为植冠宿存不变型、土壤储存增强型,土壤储存明显提高水栒子种子萌发速率;达乌里胡枝子(Lespedeza davurica)和狼牙刺(Sophora davidii)种子萌发力表现为植冠宿存增强型、土壤储存减弱型,种子萌发历时表现为植冠宿存延长型,土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时;茭蒿(Artemisia giralaii)和铁杆蒿(Artemisia gmelinii),种子萌发率随植冠宿存时间先升高后降低,随土壤储存时间先降低后升高,土壤储存可推迟其萌发,铁杆蒿种子萌发速率在植冠与土壤储存后均加快;紫丁香(Syringa oblata)种子萌发率随植冠宿存先升高后降低,土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区,植物种子经过植冠或土壤种子库储存,或增加、加快、提早萌发充分利用有利条件提高占据性,或减少、减缓、推迟萌发分摊不利条件的风险;而且该区植物植冠与土壤储存后种子萌发特性间的关系,体现各自适应环境与应对干扰的分工与协作策略,主要表现为:单一主导型和相辅相成型。     

三种植物生长调节剂对降香黄檀种子发芽的影响

采用三种植物生长调节剂GA3、IBA和6-BA不同浓度按正交设计方法,搭配处理组合,对降香黄檀种子进行处理,通过对种子发芽率、发芽势和发芽指数指标的测定,研究不同浓度的植物生长调节剂对珍贵用材树种降香黄檀种子萌发的影响。结果表明:3种植物生长调节剂浸种对降香黄檀种子萌发以6-BA的促进效果较好,GA3次之,而IBA对降香黄檀种子的发芽促进作用不明显,以处理组合6-BA50mg/L6h为最优,显著提高种子的萌发率。     

Effect of phylogeny, life history and habitat correlates on seed germination of 69 arid and semi-arid zone species from northwest China

We tested the effects of phylogeny, life history and habitat conditions for seedling establishment on seed germination of 69 arid/semi-arid zone species from northwest China. Final germination percentages had a bimodal distribution, whereas, days to first germination were skewed toward short periods. Stepwise multi-way ANOVAs showed that the amount of variance in final germination percentage among species for seeds incubated in light was explained by phylogeny (13.6%), dispersal mode (11.9%), seed mass (3.6%), and habitat (0.2%); in darkness by dispersal mode (17.5%), phylogeny (12.7%), seed mass (5.7%), and habitat (0%). A series of ANOVAs revealed that the variance in final germination percentages among species is largely dependent upon phylogeny and dispersal mode but that it is also influenced by seed mass and habitat. The effects of dispersal mode and seed mass on final germination percentage among species were phylogenetic group- and habitat-specific. Wind-dispersed seeds had higher germination percentages than unassisted and vertebrate-dispersed seeds. Compared to xerophytes, mesophytes tended to have smaller seed mass, higher mean germination percentages and a greater effect of seed mass on final germination fractions. Our results suggest that phylogeny and life history should be taken into account in studies on the role of natural selection in regulation of seed germination.     

INTERACTION OF TEMPERATURE AND GIBBERELLIN ON POTATO SEED GERMINATION

Recently harvested true seed of potato frequently requires several months for complete germination. Gibberellic acid (GA₃) has a pronounced effect on seed germination, but this effect is influenced by temperature. As the temperature approaches 80 F, germination decreases considerably irrespective of GA₃ treatment. Potato seed germination is also favored by low temperature, but constant low temperature alone does not insure complete germination of dormant seeds. More than 95% germination of dormant seeds can be obtained within a week either by application of GA₃ at low temperature or by diurnal alternation of temperature. A possible mechanism for control of seed germination is discussed.     

Proanthocyanidins Inhibit Seed Germination by Maintaining a High Level of Abscisic Acid in Arabidopsis thaliana

Proanthocyanidins (PAs) are the main products of the flavonoid biosynthetic pathway in seeds, but their biological function during seed germination is still unclear. We observed that seed germination is delayed with the increase of exogenous PA concentration in Arabidopsis. A similar inhibitory effect occurred in peeled Brassica napus seeds, which was observed by measuring radicle elongation. Using abscisic acid (ABA), a biosynthetic and metabolic inhibitor, and gene expression analysis by real-time polymerase chain reaction, we found that the inhibitory effect of PAs on seed germination is due to their promotion of ABA via de novo biogenesis, rather than by any inhibition of its degradation. Consistent with the relationship between PA content and ABA accumulation in seeds, PA-deficient mutants maintain a lower level of ABA compared with wild-types during germination. Our data suggest that PA distribution in the seed coat can act as a doorkeeper to seed germination. PA regulation of seed germination is mediated by the ABA signaling pathway.     

The use of image analysis to monitor the germination of seeds of broccoli (Brassica oleracea) and radish (Raphanus sativus)

To study broccoli and radish seed germination under different temperature regimes the germination test has been used to assess final germination percentage, start and rate. This method has been integrated with a computer‐aided image analysis test which is more accurate in monitoring the extent of imbibition phases through the assessment of seed area increase and timing of radicle emergence detected on single seeds. In addition, seed area increase has been used also to establish a close relationship with radicle elongation rate in the time range when ‘visible germination’ is scored by a classical germination test. The results suggest that this image analysis parameter may be considered as a reliable seed imbibition marker to integrate the germination parameters obtained by a germination test.     

条叶百合种子萌发的研究

研究了不同光、温对条叶百合(Lilium callosum)种子萌发的影响。研究结果表明:(1)避光条件下温度对栽培4年生条叶百合种子萌发影响最大,其种子萌发最适宜温度为25℃, 4~5天开始萌动, 1~2周萌发完全。随着温度的升高或降低其种子萌发率下降。但在5℃时萌发率又有大幅升高, 35℃种子萌发完全受到抑制。(2)同一果序不同位置果实的种子萌发以最下部果实为好,中间果实次之,上部最差。(3)同一果实内中部种子萌发最好,下部种子次之,上部种子最差,上、中、下三部分种子萌发率与其千粒重呈正相关。(4)在相同实验条件下,野生条叶百合与栽培4年生条叶百合种子萌发率一致,但萌发完全时间比栽培条叶百合多14天。(5)贮藏一年后条叶百合种子萌发率没有下降。     

Hormonal and temperature regulation of seed dormancy and germination in <Emphasis Type="Italic">Leymus chinensis</Emphasis>

Fluctuating temperature plays a critical role in determining the timing of seed germination in many plant species. However, the physiological and biochemical mechanisms underlying such a response have been paid little attention. The present study investigated the effect of plant growth regulators and cold stratification in regulating Leymus chinensis seed germination and dormancy response to temperature. Results showed that seed germination was less than 2 % at all constant temperatures while fluctuating temperature significantly increased germination percentage. The highest germination was 71 % at 20/30 °C. Removal of the embryo enclosing material of L. chinensis seed germinated to 74 %, and replaced the requirement for fluctuating temperature to germinate, by increasing embryo growth potential. Applications of GA₄₊₇ significantly increased seed germination at constant temperature. Also, inhibition of GA biosynthesis significantly decreased seed germination at fluctuating temperatures depending upon paclobutrazol concentration. This implied GA was necessary for non-dormant seed germination and played an important role in regulating seed germination response to temperature. Inhibition of ABA biosynthesis during imbibition completely released seed dormancy at 20/30 °C, but showed no effect on seed germination at constant temperature, suggesting ABA biosynthesis was important for seed dormancy maintenance but may not involve in seed germination response to temperature. Cold stratification with water or GA₃ induced seed into secondary dormancy, but this effect was reversed by exogenous FL, suggesting ABA biosynthesis during cold stratification was involved in secondary dormancy. Also, cold stratification with FL entirely replaced the requirement of fluctuating temperature for germination with seeds having 73 % germination at constant temperature. This appears to be attributed to inhibition of ABA biosynthesis and an increase of GA biosynthesis during cold stratification, leading to an increased embryo growth potential. We suggest that fluctuating temperature promotes seed germination by increasing embryo growth potential, mainly attributed to GA biosynthesis during imbibitions. ABA is important for seed dormancy maintenance and induction but showed less effect on non-dormant seed germination response to temperature.     

Seed germination traits of desert perennials

While understanding that seed germination is crucial for ecological restoration activities, the seed traits of desert perennials are understudied. We experimentally determined germination traits of 43 species from 14 families from Hummock grasslands in the Great Sandy Desert, Australia. We defined morphological and physiological seed traits of framework species required for restoration and investigated the effects of fire and temperature on seed germination. We classified dormancy and explored the effect of Karrikinolide, a fire cue derived from smoke, on germination. Seeds of 38 (88%) out of 43 species were dormant: 13 (30%) with physical and 25 (58%) with physiological dormancy. Karrikinolide promoted seed germination of 9 (21%) species across all life-forms except trees, and widened the range of germination temperatures and increased germination rate of one species. Although high germination percentages were obtained over a wide temperature range, germination rate was affected by temperature. Non-dormant seeds and seeds pre-treated to overcome physical dormancy germinated quickly, with times to 50% germination of 1–5 days. Dormancy class differed between life-forms and families. Fast germination of non-dormant seeds is a trait that allows seeds to germinate during short periods of moisture availability. An absence of under-developed embryos is consistent with the global trends for hot deserts. A response to Karrikinolide shows that seed germination is related to a fire cue. These results will inform land managers of effective seed pre-treatments prior to seed broadcasting for restoration, and information on seed germination temperatures and rates will improve the understanding of when and where seeds could germinate in restored sites.     

荒漠植物种子逆境萌发研究进展

对水分、温度、光照、沙埋深度、盐分胁迫及以上几种综合因素在逆境条件下对荒漠植物种子萌发的影响进行了综述。降雨次数、雨量大小、分布及土壤湿度是决定荒漠植物种子萌发的重要生态因子;温度是影响荒漠植物种子萌发的关键生态因子之一,变温有利于荒漠植物种子萌发;光照并非大多数荒漠植物种子萌发的必要条件,少部分荒漠植物种子萌发需要光照,有些要在黑暗中萌发,有些则对光照无特殊要求,光照对有些荒漠植物种子萌发有一定的抑制;不同沙埋深度具有不同的土壤湿度,土壤温度和光照等条件,综合调控荒漠植物种子的萌发;盐分胁迫抑制种子的萌发。荒漠植物种子的萌发在以上几种因素的共同协调作用下表现出一定的适应性。随着研究的不断深入和生态环境建设的需求,需要加强荒漠植物生理生态研究的深度和研究的系统性。     

干旱胁迫下华北驼绒藜种子大小及苞片对萌发和幼苗生长的影响

干旱是影响荒漠区植物种子萌发和幼苗生长的关键因素.以多年生强旱生半灌木华北驼绒藜为对象,研究了不同干旱程度(0、100、200、300和400g·L-1PEG6000)下,种子大小及苞片有无对种子萌发及幼苗生长的影响.结果表明:干旱胁迫显著抑制了种子萌发和幼苗地上部的生长.100和200 g ? L-1 PEG6000...     

普甜玉米种子萌发期糖代谢和水解酶活性动态变化

种子萌发是一个较复杂的生理生化过程,是种子贮藏物质在酶的作用下经过一系列反应生成蔗糖、葡萄糖、果糖等各种糖类化合物,为种子萌发提供碳源和能量。该研究利用两个不同来源、籽粒营养成分具有差异的普甜玉米种子动态分析了种子萌发期蔗糖、果糖和葡萄糖代谢及关键水解酶活性的变化。结果表明:在种子萌发过程中,E22和T26两个普甜玉米种子的物质动员量、物质利用率、蔗糖、葡萄糖和果糖含量均存在遗传差异,其中淀粉含量较高的T26种子具有较突出的物质利用率,表明淀粉是影响普通甜玉米种子萌发的关键因子;在种子萌发4~8 d、6~10 d时,E22分别具有较高的蔗糖和葡萄糖含量,而T26是在萌发10 d时具有较高的果糖含量。随着种子发芽进程,蔗糖合成酶活性、淀粉酶活性都呈逐渐上升的趋势,但淀粉酶活性变幅较明显;进一步关联分析8个种子萌发物质利用性状间关系,结果表明种子萌发期间,种子物质动员量主要受淀粉酶活性影响,而种子物质利用率则主要受糖含量多少制约。因此,提高甜玉米种子萌发期物质利用率对其种子发芽和幼苗生长,增强其与杂草生长的竞争力,提高甜玉米产量均具有重要意义。     

How do primates affect seed germination? A meta‐analysis of gut passage effects on neotropical plants

Biotic seed dispersal is a key process maintaining biodiversity in tropical forests where most trees produce vertebrate‐dispersed seeds. Existing meta‐analyses suggest an overall positive effect of vertebrate gut passage on seed germination, but no significant effects for non‐flying mammals. However, previous meta‐analyses combined rodents (seed predators) and primates (seed dispersers) into the non‐flying mammals category, which may confound specific effects of each group on seed germination. However positive effects of monkeys on germination had previously been found in some studies. Here we disentangle the role of Neotropical primates as contributors to seed dispersal in tropical forests by running a meta‐analysis to determine the overall magnitude of gut passage effects on seed germination percentage and mean time to germination. We also compare effect sizes as a function of different feeding guilds, gut complexities, and seed size. Our results show a strong, positive effect of primates on seed germination percentage and on the number of days to first germination. Strictly frugivorous monkeys, the group most threatened by extinction, showed the highest dispersal quality, increasing germination percentage by 75%. Primates that include insects in their diets had no average effect on germination percentage or time. Gut passage had different outcomes on seeds with different sizes; both large and small seeds showed similar increases in germination percentages after gut passage, but only large seeds germinated faster than control seeds after gut passage. Our results show a relevant role for primates in providing high seed dispersal quality and as drivers of forest regeneration. The combined effects of defaunation and forest fragmentation may result in decreased regeneration of trees, which has the potential to affect negatively both forest structure and ecosystem processes. Finally, we provide general guidelines for standardizing research on seed dispersal by primates. Synthesis Consuming fleshy fruits and dispersing seeds is the main ecological service provided by vertebrates to plants. Vertebrate increases seed germination due to treatment given during digestive system passage. Previous meta‐analyses suggest an overall positive effect of vertebrate gut passage on germination, but no insights are available on its variation among different functional groups of mammals. Our analyses indicated that gut passage by Neotropical primates increased seed germination. Strict frugivores, the ones most threatened by extinction, were the most efficient. Our results show a relevant role for primates in providing high seed dispersal quality and as drivers of forest regeneration, which can be meaningful for conservation in a community scale.     

Control of seed germination by light-induced histone arginine demethylation activity

For optimal survival, various environmental and endogenous factors should be monitored to determine the appropriate timing for seed germination. Light is a major environmental factor affecting seed germination, which is perceived by phytochromes. The light-dependent activation of phytochrome B (PHYB) modulates abscisic acid and gibberellic acid signaling and metabolism. Thus far, several negative regulators of seed germination that act when PHYB is inactive have been reported. However, neither positive regulators of seed germination downstream of PHYB nor a direct mechanism for regulation of the hormone levels has been elucidated. Here, we show that the histone arginine demethylases, JMJ20 and JMJ22, act redundantly as positive regulators of seed germination. When PHYB is inactive, JMJ20/JMJ22 are directly repressed by the zinc-finger protein SOMNUS. However, upon PHYB activation, JMJ20/JMJ22 are derepressed, resulting in increased gibberellic acid levels through the removal of repressive histone arginine methylations at GA3ox1/GA3ox2, which in turn promotes seed germination.