山羊臭虎耳草的延迟自动自花授粉机制
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国家重大基础研究发展规划(973 计划)项目(2013CB429904);国家自然科学基金重大项目(31230014)


Delayed Autonomous Self-pollination in Saxifraga hirculus L.(Saxifragaceae)
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    摘要:

    通过对山羊臭虎耳草6个花形态及其发育阶段、授粉过程的连续观察和对花粉活性、柱头可授性的连续检测,报道了一种新的延迟自动自花授粉机制,即山羊臭虎耳草花丝运动引导的延迟自动自花授粉。利用电子显微镜研究了花粉囊的破裂方式和柱头结构,同时利用苏丹Ⅲ研究了花粉的组织化学性质。结果显示:(1)第四生长阶段,当花丝引导大部分花粉囊运动至柱头上方时,花粉和柱头的可授性才均达到峰值[可授性分别为(94±6)%和(96±13)%],这种运动消除了第三生长阶段花粉活性较高[(90±8)%]而柱头可授性较低[(6±17)%]的异花授粉特征,即消除了花粉与柱头的时空隔离;自动自花授粉发生于异花授粉特征消除之后,因此山羊臭虎耳草具有典型的延迟自动自交行为。(2)第四发育阶段柱头空腔的大量柱状突起和花粉鞘的油脂性特征,增加了花粉和柱头的接触表面,并且使花粉更好地互相堆积粘附在柱头上,提高授粉效率。(3)对山羊臭虎耳草的繁育系统研究表明,强制自花授粉和人工自花授粉产种量无明显差异,2007年和2008年的自交系数高达0.92和0.91,说明山羊臭虎耳草具有很好的自交能力并且不存在花粉数量限制;人工异花授粉的产种率显著高于人工自花授粉,说明自花花粉的质量显著低于异花花粉,虎耳草延迟自动自花授粉存在生殖衰退,生殖保障系数2007年为0.92,2008年为0.91,表明在极端环境下自动自花授粉为该植物提供了繁殖保障,但极端环境下,没有观察到有效的授粉昆虫。研究表明,作为高山冰缘植物的山羊臭虎耳草,保留了开花植物异花授粉的特征,在极端环境下利用延迟自动自花授粉机制完成授粉,保障生殖。

    Abstract:

    Through continuous observation of six stages of floral morphology and development,and continuous assay of pollen viability and stigma receptivity,we identified a novel mechanism of delayed autonomous self-pollination driven by filaments in Saxifraga hirculus in high arctic and alpine regions.The crack mode of anther and the stigma structure was studied by SEM,and using Sudan Ⅲ tested pollen histochemistry.The results showed that:(1)As the majority of anthers gathered above the stigma by filaments,pollen viability and stigma receptivity reach their peaks [(94±6)% and (96±13)%,respectively],then the spatio-temporal separation of pollen and stigma which termed as herkogamy came from stage 3 [the pollen viability higher to (90±8)%,however,the stigmas receptivity only (6±17)%],were eliminated in stage 4.This autonomous self-pollination occurs after outcrossing,making S.hirculus a classical case of delayed autonomous selfing.(2)Deeply concave stigmas with abundant columned papillae and oily pollenkitt got pollen together and contacted with stigmas well,increasing pollination efficiency.(3)We examined the breeding system of this species,found that there was no difference between obligate self-pollination and hand self-pollination in seed production.Indexes of autonomous selfing in 2007 and 2008 were 0.92 and 0.91,respectively.It means that S.hirculus developed a capacity of self-pollination and no pollen lamination.Significant difference between hand self-pollination and hand outcross-pollination in seed production indicating that the quality of self-pollen is lower than that of outcross-pollen and self-pollination can result in inbreeding depression.Reproductive assurance measures were 0.92 in 2007 and 0.91 in 2008 indicating selfing provided reproductive assurance.No effective pollinators were found.These results showed that as a glacial relict,S.hirculus has developed a capacity for delayed autonomous selfing while retaining partial characteristics of outcrossing from its ancestors,and provided reproductive assurance in rough weather conditions.

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李东明,封建新,曾定军,等.山羊臭虎耳草的延迟自动自花授粉机制[J].西北植物学报,2013,33(9):1775-1785

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  • 在线发布日期: 2013-10-09
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