南方砂梨返花过程中内源激素含量变化及其与秋季返花的关系

为探讨花芽内源激素含量变化与返花的关系,以砂梨品种‘丰水’、‘翠冠’为材料,研究了砂梨采果后返花过程中花芽内源激素(IAA、GA3、ABA)含量变化,以及早期落叶和秋季返花特征。结果表明:(1)在采果后至返花过程中,两个品种梨花芽中内源激素IAA和GA3含量都呈逐渐缓慢下降趋势;花芽ABA含量的动态变化成升-降-升的"S"曲线。(2)花芽返花受3种激素的动态平衡控制,花芽IAA/ABA、GA3/ABA和(IAA+GA3)/ABA值变化趋势均呈相似的"S"形曲线,IAA/ABA、GA3/ABA和(IAA+GA3)/ABA值增加,花芽返花;比值降低,花芽逐渐步入休眠期。(3)砂梨的落叶率与返花率呈极显著正相关关系,花芽中IAA/ABA比值与砂梨落叶率和返花率相关系数分别为0.805、0.774,相关性均达到显著水平。研究认为,梨返花与早期落叶密切相关,受花芽内源激素IAA、GA3、ABA动态平衡控制;早期落叶降低了花芽中ABA的含量,从而使花芽内生长促进型激素占主导地位,阻止自然休眠的花芽进入休眠或促使进入浅休眠部分花芽解除休眠,所以出现秋季返花现象。     

南方红豆杉种子综合处理过程中内源激素的动态变化

为揭示南方红豆杉种子内源激素与休眠的关系,采用酶联免疫吸附法(ELISA)测定了经过层积处理的种皮和胚乳的脱落酸(ABA)、赤霉素(GA3 )、吲哚乙酸(IAA)、玉米素核苷(ZR)4种内源激素含量的变化情况.结果表明:种子胚乳中内源ABA的含量随着层积时间的延长而逐渐下降,GA含量增加,IAA和ZR的含量先增加后降低...     

GA3和变温层积对天女木兰种子萌发及内源激素的影响

用不同质量浓度GA3浸泡天女木兰种子并结合变温层积处理,应用高效液相色谱法对不同时期种子中4种激素GA3、IAA、ABA、ZR含量进行测定,并测量种胚长和萌发率,以探讨天女木兰种胚发育,内源激素含量变化与种子休眠萌发之间的调控关系,为进一步研究种子休眠机理提供理论基础。结果表明:(1)天女木兰成熟种子胚发育不完全,胚乳内高浓度ABA和低浓度GA3是其休眠的主要原因。(2)GA3处理能促使天女木兰种子提前30d完成形态后熟,并以1 500mg·L-1 GA3处理效果最佳。(3)在变温层积过程,天女木兰种胚发育可分三个阶段:阶段Ⅰ(0~70d)完成种胚进一步分化;阶段Ⅱ(70~120d)种胚快速生长时期;阶段Ⅲ(120~150d)休眠完全解除,种子具备发芽能力。种子能否打破休眠主要取决于阶段Ⅰ和Ⅱ的状况。(4)GA3/ABA、IAA/ABA和ZR/ABA在种子后熟期间的变化同胚生长发育存在一致性,认为内源激素的相对水平对种子休眠具有重要的调控作用。     

剥鳞和激素处理对大樱桃花芽休眠解除及内源激素变化的影响

采用高效液相色谱法(HPLC)分析了剥鳞与激素处理对大樱桃花芽休眠解除及内源生长素(IAA)、赤霉素(GAD、玉米素(ZT)和脱落酸(ABA)变化的影响。结果表明,花芽中的ABA主要分布于鳞片内,鳞片中的GA3和ZT含量远低于去鳞芽,也低于完整芽。剥鳞能明显增加休眠花芽中内源GA2和ZT的含量,降低ABA的含量,对IAA含量的影响不大。剥鳞降低了ABA／GA3、ABA／ZT的比值,使花芽向促进生长、抑制休眠的方向转化。同时,休眠前、后期剥鳞均能明显提高萌芽率,中期剥鳞效果不明显。剥鳞后施用外源激素随休眠时期不同而有不同的破眠效果,早期剥鳞GA3的效果最好,6-BA次之,IAA最差;中期破眠效果不如早期,GA。和6-BA没有明显差别;后期以6-BA效果最好,其次是GA3和IAA;3次处理中ABA均明显抑制花芽萌发。     

ABA,GA对芸苔属种子休眠与萌发的调控研究(简报)

深休眠与浅休眠的两类芸苔属遗传资源中,内源激素含量明显不同。种子萌发时,内源GA迅速增加、ABA急剧减少。种子经外源(±)ABA溶液预浸后,体内ABA含量增加,并随处理时间延长和浓度提高呈上升趋势。引起90％浅休眠种子萌发阻抑的外源ABA浓度为1000ppm。200ppmGA_3能够有效地逆转ABA诱导的强迫休眠。     

小花草玉梅种子萌发过程中常见内源激素含量的变化及萌发机制

植物内源激素在调节种子休眠和萌发过程中具有极其重要的作用。本研究运用反式高效液相色谱(RP-HPLC)与紫外检测器联用的方法对小花草玉梅干种子、吸胀种子和露白种子中的赤霉素GAs、脱落酸ABA、玉米素ZT和生长素IAA含量进行了检测,旨在研究植物内源激素水平在种子萌发过程中的变化是否直接关系着小花草玉梅种子在光照或黑暗条件下的萌发能力。结果显示,种子吸胀过程中,光照促进了ZT同时抑制了ABA的积累,并且ZT对ABA萌发抑制作用的解除也受光的促进,露白种子中的ABA/ZT,ABA/GAs和(ABA+IAA)/(GAs+ZT)水平在黑暗条件下高于光照条件,上述均是导致光照条件下种子萌发率较高的重要原因;相对于干种子,IAA含量在种子吸胀初期急速下降,(ABA+IAA)/(GAs+ZT)在种子萌发过程中有所降低,而ABA/GAs却表现出明显的上升趋势;各激素水平所受光照的影响均在种子开始露白时显著减弱,另外,吸胀第9天是小花草玉梅种子萌发过程中激素变化的一个关键的时间节点。总之,种子萌发并非直接关系着GA含量的升高和ABA含量的降低。因光照直接促进了小花草玉梅种子的萌发,本研究认为高寒草甸充足的光照和较强的太阳辐射通过调节种子内源激素水平在一定程度上对种子萌发过程中的休眠解除具有重要作用。     

梾木种子低温层积过程中内源激素含量的动态变化特征

应用酶联免疫吸附测定法(ELISA)研究了梾木种子低温层积过程中内源激素含量的动态变化,分析了内源激素与种子休眠与发芽的关系。结果表明:(1)梾木种子中IAA含量在层积处理初期剧烈降低,持续一段时间后又显著升高,但后期下降,且IAA/ABA也出现同样的变化;种子中ABA含量在层积处理前期较高,但随着处理时间的延长趋于下降;种子内GA1/3含量以及GA1/3/ABA均随层积处理时间的延长逐渐增大;种子内ZRs和iPAs含量的变化相对较为平稳,尽管有一定的波动,但整体呈渐趋增高趋势。(2)梾木种子发芽率及发芽势在未经层积处理以及处理时间少于90d的条件下均为0,但随着层积处理时间的延长二者明显上升,层积处理的时间长短对梾木种子萌发有显著影响。(3)相关分析表明,梾木种子内GA1/3含量与种子的发芽率、发芽势均呈显著正相关关系,相关系数分别为0.688、0.662;种子内GA1/3/ABA增大有利于种子休眠解除和萌发。     

珍稀濒危植物金丝李种子的休眠机理

珍稀濒危植物金丝李(Garcinia paucinervis)种子的萌发十分缓慢,探讨其休眠机理,可为该物种的种质资源保育与可持续利用提供理论依据。本文对金丝李种子种皮结构及其透水性,剔除部分种皮和胚乳后种子的萌发情况,胚乳和胚等粗提物的活性,储藏、层积和不同温度下种子萌发情况,萌发过程中内源激素含量等进行了研究。结果表明:金丝李种皮无栅栏细胞层,下表面的角质层较薄;种皮对种子的吸胀阻碍小;随着种孔端剔除种皮和胚乳程度的加深,金丝李种子的萌发进程逐渐延长,甚至降低其萌发率,种脐端削除处理对种子萌发影响不大;内果皮、种皮、胚乳和胚中可能存在抑制金丝李种子萌发和生长的内源抑制物;新鲜种子胚率达86.12%,低温层积后胚率无显著变化;低温层积处理延缓其萌发进程,对萌发率无显著影响,4℃低温层积是储藏金丝李种子的较好方法;种子萌发对温度敏感,在32℃培养下可打破种子休眠,萌发速度显著加快。种子萌发过程中ABA含量降低,GA与ABA、IAA与ABA的比值随种子萌发显著升高,萌发促进与抑制物比例逐渐趋于提高。因此,金丝李种子存在内源抑制物,同时缺乏萌发促进物质,导致生理休眠。该种子休眠特性使其幼苗生长能应对生境的季节变化,种群在风险环境中得以延续,避免大量幼苗竞争。植被破坏导致种子萌发阶段受阻是造成金丝李濒危的原因之一。     

椭圆叶花锚种子内源激素对储藏的响应及其与种子萌发的关系

内源激素作为调控种子萌发与休眠的主要内因一直备受关注,但其随环境条件改变的变化规律及其对种子萌发的调节机制一直缺乏普遍接受的理论或假说。本研究以广泛分布于青藏高原东北缘高寒草甸的椭圆叶花锚种子为研究材料,分析不同储藏条件和时间对椭圆叶花锚种子内源激素含量的影响,及其与种子萌发的关系。结果表明:不同储藏条件下,椭圆叶花锚种子中内源激素含量随储藏时间变化差异显著;常温条件下,储藏时间对内源激素的绝对含量及各生长促进物与抑制物的比值(IAA/ABA除外)均有较显著的影响,而在冷藏条件下,储藏时间仅对GAs、IAA、ABA和促进物总量有较显著的影响;储藏条件和时间对椭圆叶花锚种子的萌发率均有极显著影响;常温储藏条件下种子萌发率大约是冷藏条件下的4倍,且种子存在休眠循环;椭圆叶花锚种子萌发并不是促进类激素或抑制类激素绝对含量的升降调节的;种子萌发与GAs含量显著正相关、与IAA含量显著负相关,CTK的含量达到一定高度的时候,萌发率才能达到最高。因此,本研究中各内源激素的作用关系,与Khan提出的三因子学说相一致,即CTK与ABA相拮抗,减轻或消除ABA的萌发抑制作用,从而使GAs的作用表现出来。     

山楂种子休眠与后熟期间内源激素的变化（简报）

山楂种子必须经过低温层积后方可发芽。剥去种子外壳可以缩短山楂低温层积时间。山植种子发芽随着种子中ABA含量降低,GA3、ZR和IAA含量增加,以及GA3／ABA、IAA／ABA、ZR/ABA比值增大而增加,休眠解除。     

Role of endogenous hormones,glumes, endosperm and temperature on germination of Leymus chinensis (Poaceae) seeds during development

Aims Leymus chinensis is an original dominant plant in the Songnen grassland, and it has great value for restoration of severely degraded land. However, seeds are dormant, and low germination percentage is a problem for restoring L.chinensis grassland. The mechanism of seed dormancy is not been well understood. The primary aims of the present study were to investigate the dormancy mechanism of L.chinensis seeds (caryopses) with reference to the role of embryo-covering layers, endogenous hormones and temperature.Methods Changes in concentration of the endogenous hormones GA 3, indoleacetic acid (IAA), zeatin riboside (ZR) and abscisic acid (ABA) in L.chinensis seeds from anthesis to maturity were measured by the enzyme-linked immunosorbent assay method. Germination at different stages of maturity were tested at 16/28°C, 5/28°C and 5/35°C for intact seeds with glumes (control), intact seeds with glumes removed (naked-whole seeds) and intact seeds with glumes and one-half of the endosperm removed (naked-half seeds).Important findings Of the four endogenous hormones monitored, only the concentration of ZR differed significantly between the beginning and the end of seed development (increased); the GA 3 /ABA ratio also did not differ. Rank of germination percentage of control at the three temperature regimens was 5/28°C> 16/28°C> 5/35°C. Germination percentage of the naked-half seeds reached 100% under the three temperature regimens. We concluded that dormancy of L.chinensis seeds is not mainly controlled by endogenous hormones. Germination temperature, mechanical resistance of glumes and inhibition of endosperm are the main factors controlling dormancy and germination of L.chinensis seeds.     

A role for brassinosteroids in germination in Arabidopsis

This paper presents evidence that plant brassinosteroid (BR) hormones play a role in promoting germination. It has long been recognized that seed dormancy and germination are regulated by the plant hormones abscisic acid (ABA) and gibberellin (GA). These two hormones act antagonistically with each other. ABA induces seed dormancy in maturing embryos and inhibits germination of seeds. GA breaks seed dormancy and promotes germination. Severe mutations in GA biosynthetic genes in Arabidopsis, such as ga1-3, result in a requirement for GA application to germinate. Whereas previous work has shown that BRs play a critical role in controlling cell elongation, cell division, and skotomorphogenesis, no germination phenotypes have been reported in BR mutants. We show that BR rescues the germination phenotype of severe GA biosynthetic mutants and of the GA-insensitive mutant sleepy1. This result shows that BR stimulates germination and raises the possibility that BR is needed for normal germination. If true, we would expect to detect a germination phenotype in BR mutants. We found that BR mutants exhibit a germination phenotype in the presence of ABA. Germination of both the BR biosynthetic mutant det2-1 and the BR-insensitive mutant bri1-1 is more strongly inhibited by ABA than is germination of wild type. Thus, the BR signal is needed to overcome inhibition of germination by ABA. Taken together, these results point to a role for BRs in stimulating germination.     

外源赤霉素对紫斑牡丹种子萌发的影响

以紫斑牡丹种子为试验材料,研究不同浓度的赤霉素(GA_3)处理对种子生根以及生根过程中营养物质、酶活性和内源激素水平变化的影响,为探讨紫斑牡丹种子萌发机制提供依据。结果表明:(1)GA_3处理能够促进种子生根,并以300 mg/L GA_3处理对种子生根效果最好,与对照相比可提前14.67 d生根,生根率可达71.00%。(2)与对照相比,GA_3处理可以在0～15 d时促进种子淀粉水解和可溶性糖的积累,并加速可溶性蛋白的消耗,在0～30 d促进过氧化物酶(POD)活性的提高,从而促进种子萌发生根。(3)在种子沙藏生根过程中,种子脱落酸(ABA)含量呈下降趋势,赤霉素(GA)、玉米素核苷(ZR)和吲哚乙酸(IAA)含量均表现出先上升后下降的趋势,与对照相比,GA_3处理可使种子GA、ZR和IAA的含量在沙藏前期明显上升,以解除种子休眠。研究发现,外源GA_3处理可以调控紫斑牡丹种子内源激素含量和POD活性的变化,促进营养物质转化,从而提前解除种子休眠使其萌发。     

温水浸种对杜仲种子萌发过程中保护酶活性及内源激素含量变化的影响

探讨杜仲（Eucommia ulmoides Oliver）种子萌发过程中保护酶活性及内源激素含量的变化，为其种子破眠及萌发不同时期采取有效处理措施，从而提高出苗率提供参考。利用室温（CK）、40℃、50℃、60℃和70℃不同水温，探讨温水浸种对杜仲种子萌发的影响。种子萌发进程中，利用常规生理生化方法测定种子内超氧化物歧化酶（SOD）、过氧化物酶（POD）活性和丙二醛（MDA）含量，以及酶联免疫法测定赤霉素（GA₃）、吲哚乙酸（IAA）、脱落酸（ABA）和玉米素核苷（ZR）含量。结果表明：①温水浸种处理能提高了杜仲种子的发芽率及发芽势，其中以50℃温水处理最为显著。②与室温浸种处理相比，50℃温水浸种处理提高了种子内SOD及POD活性，减轻了质膜氧化损伤程度，致使MDA含量的持续下降，从而促使种子朝向有利于萌发的方向发展。此外，50℃温水浸种处理在提高种子内促进生长内源GA₃、IAA及ZR含量的同时，并降低了抑制生长的内源ABA含量，致使GA₃/ABA、IAA/ABA和ZR/ABA值均明显高于室内浸种处理，最终促进了杜仲种子的萌发。     

Molecular mechanisms and hormonal regulation underpinning morphological dormancy: a case study using Apium graveolens (Apiaceae)

Underdeveloped (small) embryos embedded in abundant endosperm tissue, and thus having morphological dormancy (MD) or morphophysiological dormancy (MPD), are considered to be the ancestral state in seed dormancy evolution. This trait is retained in the Apiaceae family, which provides excellent model systems for investigating the underpinning mechanisms. We investigated Apium graveolens (celery) MD by combined innovative imaging and embryo growth assays with the quantification of hormone metabolism, as well as the analysis of hormone and cell-wall related gene expression. The integrated experimental results demonstrated that embryo growth occurred inside imbibed celery fruits in association with endosperm degradation, and that a critical embryo size was required for radicle emergence. The regulation of these processes depends on gene expression leading to gibberellin and indole-3-acetic acid (IAA) production by the embryo and on crosstalk between the fruit compartments. ABA degradation associated with distinct spatiotemporal patterns in ABA sensitivity control embryo growth, endosperm breakdown and radicle emergence. This complex interaction between gibberellins, IAA and ABA metabolism, and changes in the tissue-specific sensitivities to these hormones is distinct from non-MD seeds. We conclude that the embryo growth to reach the critical size and the associated endosperm breakdown inside MD fruits constitute a unique germination programme.     

Role of warm stratification in promoting germination of seeds of Empetrum hermaphroditum (Empetraceae), a circumboreal species with a stony endocarp

The broad objective of this research was to define the role of warm (≥15°C) stratification in breaking dormancy in seeds with stony endocarps that require warm-plus-cold (～0°-10°C) stratification for germination. This question was addressed using seeds (true seed + endocarp, hereafter called seeds) of Empetrum hermaphroditum. Only 2-5% of freshly matured seeds collected in September and October at five sites in Sweden germinated in light at daily alternating temperature regimes of 15°/6°, 20°/10°, and 25°/15°C. Dormancy was not due to impermeability of the stony endocarp surrounding each seed, and embryos did not grow prior to radicle emergence. Thus, seeds did not have physical, morphological, or morphophysiological dormancy. Long periods of either cold stratification (20 or 32 wk) or warm stratification (16 wk) resulted in a maximum of 22-38 and 10% germination, respectively, in light at 25°/15°C. After 12 wk warm stratification plus 20 wk cold stratification, 83-93% of the seeds germinated in light at the three temperature regimes. For a cold stratification period of 20 wk, germination increased with increase in length of the preceding warm stratification treatment. Gibberellic acid (GA(3)) promoted germination of 77-87% of the seeds. Based on dormancy-breaking requirements and response to GA(3), 62-78% of the seeds had intermediate physiological dormancy; the others had nondeep physiological dormancy. Contrary to suggestions of several other investigators that warm stratification is required to make the endocarp permeable to water via its breakdown by microorganisms, our results with E. hermaphroditum show that this is not the case. In this species, warm stratification is part of the dormancy-breaking requirement of embryos in seeds with intermediate physiological dormancy.     

The etr1-2 mutation in Arabidopsis thaliana affects the abscisic acid, auxin, cytokinin and gibberellin metabolic pathways during maintenance of seed dormancy, moist-chilling and germination

In Arabidopsis thaliana, the etr1-2 mutation confers dominant ethylene insensitivity and results in a greater proportion of mature seeds that exhibit dormancy compared with mature seeds of the wild-type. We investigated the impact of the etr1-2 mutation on other plant hormones by analyzing the profiles of four classes of plant hormones and their metabolites by HPLC-ESI/MS/MS in mature seeds of wild-type and etr1-2 plants. Hormone metabolites were analyzed in seeds imbibed immediately under germination conditions, in seeds subjected to a 7-day moist-chilling (stratification) period, and during germination/early post-germinative growth. Higher than wild-type levels of abscisic acid (ABA) appeared to contribute, at least in part, to the greater incidence of dormancy in mature seeds of etr1-2. The lower levels of abscisic acid glucose ester (ABA-GE) in etr1-2 seeds compared with wild-type seeds under germination conditions (with and without moist-chilling treatments) suggest that reduced metabolism of ABA to ABA-GE likely contributed to the accumulation of ABA during germination in the mutant. The mutant seeds exhibited generally higher auxin levels and a large build-up of indole-3-aspartate when placed in germination conditions following moist-chilling. The mutant manifested increased levels of cytokinin glucosides through zeatin-O-glucosylation (Z-O-Glu). The resulting increase in Z-O-Glu was the largest and most consistent change associated with the ETR1 gene mutation. There were more gibberellins (GA) and at higher concentrations in the mutant than in wild-type. Our results suggest that ethylene signaling modulates the metabolism of all the other plant hormone pathways in seeds. Additionally, the hormone profiles of etr1-2 seed during germination suggest a requirement for higher than wild-type levels of GA to promote germination in the absence of a functional ethylene signaling pathway.