【作者】 陆婷；

【导师】 谭敦炎；

【作者基本信息】 新疆农业大学 ， 草业科学， 2010， 博士

【摘要】 异翅独尾草(Eremurus anisopterus Regel)和粗柄独尾草(E. inderiensis Regel)是百合科独尾草属的多年生短命植物。在我国,两物种同域分布在准噶尔盆地的古尔班通古特沙漠中,它们在花部特征上有明显的区别,本文以两种植物同域分布的自然分布区为研究地点,着眼于以下一些问题:(1)两个同域分布的近缘种生殖隔离的机制是什么?(2)两种植物不同的花粉呈现式样分别具有何种适应意义?(3)异翅独尾草雌全同株性系统的适应意义;(4)粗柄独尾草结实结籽特点及限制因素。通过研究,得到以下主要结论:1.异翅独尾草和粗柄独尾草花期在不同年份间有不同程度的花期重叠;两种独尾草具有不同的传粉综合征,虽然访花昆虫种类相似,但主要传粉者不同;种间交互授粉试验未能获得果实,荧光显微观察发现两种独尾草的花粉均不能在对方柱头上萌发。结果表明花期隔离和花部隔离对于阻止种间的花粉交流有重要的作用,但这两种外部隔离机制是不彻底的,结合内在的隔离机制是避免生殖干扰和保持物种独立性的必要途径。2.异翅独尾草和粗柄独尾草进化出多种控制花粉呈现的机制,相似之处在于二者都采取了花药“拉链式”纵裂的分摊机制,不同之处主要体现在:(1)异翅独尾草单花开放时间相对集中,高峰期出现在12:00,而粗柄独尾草的相对分散,在12:00和18:00出现两个高峰期;(2)异翅独尾草六枚雄蕊几乎同时散粉,而粗柄独尾草六枚花药依次开裂,全部花药开裂历时30h;(3)异翅独尾草不分泌花蜜,而粗柄独尾草为传粉者提供花蜜作为报酬,花蜜量在开花过程中逐渐累积,花蜜量影响着觅蜜昆虫的访花时间。3.异翅独尾草传粉者访问频率低,但传粉效率高,粗柄独尾草昆虫访花频率高,但传粉效率低;异翅独尾草的湿型柱头与花粉同时呈现,为混合的交配系统,有自动自花传粉的繁殖保障机制,而粗柄独尾草柱头为少见的“特殊湿型柱头”类型,柱头可授性发生在所有花药散粉之后,为虫媒专性异交植物,这些特性表明异翅独尾草采取了“花粉同时呈现(synchronous pollen presentation)”的策略,而粗柄独尾草则采取了“花粉逐步呈现(gradual pollen presentation)”的策略,花粉同时呈现的策略是对沙漠早春不可靠的传粉昆虫数量和高效的传粉效率的适应,花粉逐步呈现的式样则是对拜访者低传粉效率和访花频率高的适应,研究结果支持花粉呈现理论。4.异翅独尾草种群内同时存在雌全同株个体和两性花个体,雌花位于总状花序的基部,最早开放,雌花形态显著大于两性花;雌全同株性系统的发生是个体大小依赖的,雌花数量与叶片数量、叶片生物量、花序长度及花序上的总花数呈显著正相关;自然条件下雌花和两性花结实率没有显著差异,但两性花结籽率显著高于雌花;人工异花授粉可以显著提高雌花和两性花的结实率和结籽率,且二者间没有显著差异。异翅独尾草大个体雌全同株性系统的可能适应意义是在保证一定数量后代的前提下,增加雌性投入,通过得到更多杂交后代从而提高个体适合度。5.粗柄独尾草初花期的结实率最高,其次是盛花期,末花期结实率最低;盛花期花展示最大,结实率与花展示大小呈正相关;天气状况影响花展示大小和昆虫访问频率,从而也对结实率产生影响;花序长度和花序总产花量与结实率没有显著相关性;花序基部花和中部花的花粉量、P/O值、结实率和结籽率没有显著差异,但显著高于顶部花的。以上结果表明粗柄独尾草顶部花结实更容易受到资源限制,顶部花结实率低是选择性败育的结果,是对沙漠恶劣生存环境的适应策略之一。更多还原

【Abstract】 Eremurus inderiensis (M. Bieb) Regel and E. anisopterus (Kar. et Kir) Regel are herbaceous perennial spring ephemeral of Liliaceae, and in China they only distribute in Gurbantunggut Desert of Xinjiang. There are discernible differences between two sympatric Eremurus species in floral characters. In this study, we had chosen the location where two Eremurus species distributed sympatric to focus on the questions as follow: (1) the reproductive isolation mechanism between them; (2) the evolutionary implication of two kinds of pollen presentation patterns; (3) adaptive advantages of size-dependent gynomonoecious on E. anisopterus; (4) patterns and limitation factor on fruit set and seed set of E. inderiensis. Over few years’field observations and manual experiments, we have drawn some results as follows:1. There was different degree of overlap on flowering period between two E. anisopterus and E. inderiensis in different years. Two species with different floral design have different pollination syndrome. Variation in floral design indicated that two Eremurus species suit for different type of pollinators although they were visited by almost the same series of insects. There was not any seed yield under the control of artificial hybridization. Thorough the observation under the fluorescence microscope, the pollens from E. anisopterus and E. inderiensis did not germinate on each other’s stigmas. The results indicated that temporal isolation and floral isolation are important to prevent the gene exchange between taxa, but the two external isolation mechanisms were uncompleted, and combined with internal isolation mechanism was the essential way to maintain sympatric related species boundary in Eremurus .2. Several mechanisms were evolved to control the pollen presentation in E. anisopterus and E. inderiensis. The similarity lies in the fact that two species dispensing pollen by unzipping the anthers. What the distinction between two species were: (1) the peak of flower opening time of E. anisopterus appeared at 12:00, whereas two peaks arose at 12:00 and 18:00 in E. inderiensis; (2) the six anthers within a flower of E. anisopterus shed the pollens at almost the same time, but six anthers within a flower of E. inderiensis presented pollens one by one during about 30h; (3) the flowers of E. anisopterus do not secret the nectar, but the flowers of E. inderiensis provide the nectar to the pollinators as rewards. The volume of nectar accumulated constantly during the flowering course, and related with the length of a flower visit.3. To the E. inderiensis, E. anisopterus was visited by rare pollinators , but pollinated in high efficiency. E. anisopterus has wet stigma and the pollen presentation and stigma presentation occurred at the same time. This species is self-compatible and the pollen could be autonomously transferred to the stigma within flowers. High fruit set by hand cross pollination showed E. anisopterus had the mixed mating system. E. inderiensis has a special type of‘wet’stigma, where a secretion accumulates under the cuticle. When the cuticle rupture, the secretion was released and the stigma acquired the receptivity. This species has the outcrossing mating-system and the fertilization depend on the insect pollination. Synchronous pollen presentation of E. anisopterus should be a strategy to insure reproductive success under the early spring in desert where the pollinators are unreliable and efficient at delivering the pollen they remove. The gradual pollen presentation of E. inderiensis should be related with the abundant pollinator and inefficient at delivering the pollen they remove. The results supported PPT (Pollen presentation theory).4. There were two kinds of individual plants in population of E. anisopterus, individual plants had both female and hermaphrodite flowers and individual plants only hermaphrodite flowers. Gynomonoecy sexual system in E. anisopterus was size-dependent, and the number of female flowers in an individual plant was positive correlate with number of leaves, dry weights of leaves, length inflorescence, and total flowers in an inflorescence. The female flowers located at the base, bloomed earliest in an inflorescence and were significant bigger than hermaphrodite flowers. There was non significant difference on the fruit-set percentage between female flowers and hermaphrodite flowers, but seed-set percentage of female was significant higher than that of perfect flowers. Hand cross-pollination could improve the fruit-set ratio and S/O significantly. Adaptive advantages of size-dependent gynomonoecious in E. anisopterus might be a strategy to enhance fitness of individuals by allocated more resources to female function and sired more outcrossing offspring under ensuring certain number of offspring.5. The fruit-set pattern of E. inderiensis was studied and the results showed: (1) fruit-set percentage was highest for ?owers opened in the beginning of the blooming season, followed by the flowers in the middle of flowering season, and the lowest fruit-set was the flowers in the late blooming season. (2) the floral display size was largest in middle blooming season and small in both early and late blooming season. Fruit-set percentage was positively correlated with floral display size. (3) the weather condition influenced the floral display size and frequency of insect visitation, and therefore exerted an influence on fruit-set. (4) fruit-set percentage had no significantly correlated with length of inflorescence and total number of flowers in an inflorescence. (5) the number of pollens, P/O, fruit-set percentage and seed-set percentage between flowers at bottom and in the middle of the inflorescence did not exist the significant differences, but significant higher than those of the flowers at top of the inflorescence. These results indicated that the fruit set of the flowers on the top of the inflorescence were limited by resources more easily. The low fruit-set of the flowers on the top of the inflorescence might be the result of selective abortion and one of strategies to desert environment.更多还原