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题名: 铃铛子(Anisodus luridus)和赛莨菪(A. carniolicoides)的传粉机制与生态适应
作者: 王赟
学位类别: 硕士
答辩日期: 2009-05-10
授予单位: 中国科学院昆明植物研究所
授予地点: 昆明植物研究所
导师: 许建初
关键词: 交配系统 ; 自交亲和性 ; 传粉效率 ; 花方向 ; 花粉活力 ; 降雨 ; 宿存花萼 ; 青藏高原
学位专业: 植物学
中文摘要: 自交不亲和性是有花植物避免自交的一种有效的生理机制,但在不利的异花传粉环境中,植物的自交不亲和系统可能崩溃而引起自交以保障有性繁殖。从异交到自交的转变是被子植物交配系统进化的主要趋势,而比较同一属内不同物种的传粉机制有助于揭示交配系统的进化和转变。山莨菪属(Anisodus)是茄科的一个小属,是中国-喜马拉雅特有类群。本研究以山莨菪属的铃铛子(A. luridus Link)和赛莨菪(A. carniolicoides (C. Y. Wu and C. Chen) D'Arcy and Z. Y. Zhang)为研究对象,通过野外交配系统试验和传粉昆虫观察,探讨了山莨菪属内自交亲和系统的进化与传粉昆虫的转变;并通过研究两种植物在开花时期花梗下弯而铃铛子在果期花梗直立的现象与高山环境中生态因子的关系,探讨两种植物对高山环境的适应机制。结果表明: 1. 铃铛子和赛莨菪自交和异交的座果率与种子数没有显著差异,表明两种植物是自交完全亲和的类群;不去雄套袋较低的座果率和种子数证明两个种都具有一定自动自交的能力;自然状态下补授异花花粉显著提高了两种植物的座果率和种子数,说明两种植物均存在传粉限制。北方黄胡蜂(Vespula rufarufa L.)和石长黄胡蜂(Dolichovespula saxonica Fabr.)分别是铃铛子和赛莨菪的主要传粉昆虫,北方黄胡蜂访问铃铛子的频率显著高于石长黄胡蜂访问赛莨菪的频率。以一天(10:00-17:00, 7 h)内柱头上落置的花粉数量评价昆虫的总传粉效率,发现自然状态下两种昆虫的总传粉效率均比较高,但去雄后赛莨菪柱头上的花粉数量显著降低,而铃铛子柱头上的花粉数量则变化不大。因此推测两种昆虫访问两种植物时传递花粉的方式不同:北方黄胡蜂主要促进了铃铛子不同花之间的传粉,而石长黄胡蜂访花则引起赛莨菪同一朵花内的传粉。通过与该属另一种植物山莨菪(A. tanguticus (Maxim.) Pascher)的传粉机制(自交不亲和/自交部分亲和的物种,熊蜂、苍蝇和蚂蚁为该植物传粉昆虫)比较,并结合该属的系统发育关系,发现在山莨菪属的物种分化过程中,自交不亲和转变为自交完全亲和,证明了自交亲和系统存在于起源较晚的类群中;传粉昆虫也发生了转变。而高山环境中频繁且不可预测的降雨可能降低了传粉昆虫的活动能力及稳定性,导致铃铛子和赛莨菪均存在传粉限制。 2. 铃铛子和赛莨菪的花梗都在花期下垂,而授粉后在种子和果实的形成发育期,铃铛子的花梗由下弯变为直立且花萼增大增厚,但赛莨菪的花梗并不直立。比较传粉昆虫对自然下垂花和人工直立花的访花频率与传粉效率后发现,两个种下垂的花既没有增加对昆虫的吸引力,也没有增加昆虫的传粉效率。与自然下垂花相比,降雨显著降低了两种植物直立花雄蕊上的花粉数量。铃铛子的花粉萌发实验表明,下垂花的花粉在10%的蔗糖溶液中的萌发率显著高于在在蒸馏水中的萌发率,而直立花的花粉经过5 h的太阳照射后在10%的蔗糖溶液中的萌发率显著低于下垂花的花粉,表明雨水浸泡和太阳暴晒均能降低铃铛子的花粉活力。铃铛子的花梗在果期直立后,由于高山环境中频繁且不可预测的降雨,宿存的花萼内通常能储存一定量的积水。比较自然状态下果萼内有水的果实和人为去水的果实发现,去除果萼内的存水后,成熟种子数量、结实率和种子重量均显著降低,但种子的萌发率并未显著降低,表明宿存果萼中的雨水能使受精胚珠在一个相对稳定的微环境中发育,提高了雌性适合度。以上研究结果表明,铃铛子和赛莨菪在开花期的花梗弯曲避免了高原环境中频繁的降雨和强烈的太阳辐射对花粉的破坏;而铃铛子果期的花梗直立、果萼宿存以及由此引起的果萼内积水能减弱高原环境中较大的昼夜温差对受精胚珠发育过程的破坏作用,是对特殊高山环境的有效适应机制。
英文摘要: Self-incompatibility, the physiological inability of a fertile hermaphrodite plant to produce viable seeds upon self-pollination, is the principal and most effective mechanism preventing self-fertilization in flowering plants. However, in extremely harsh environments where pollinators are scarce and unstable, self-incompatibility might break down, followed by self-pollination to assure sexual reproduction. Since the evolution of selfing races or species from primarily outcrossing ancestors is one of the most frequent evolutionary transitions in the plant kingdom, empirical studies comparing mating systems and pollination mechanisms in closely related species within one genus will help us to better understand the evolution of plant mating system. In this dissertation, I performed field experiments on Anisodus luridus Link and A. carniolicoides (C. Y. Wu and C. Chen) D'Arcy and Z. Y. Zhang, which belongs to the Hyoscyameae in Solanaceae, attempting to explore the evolution of self-compatibility and pollinator shift in the genus Anisodus. Additionally, I also explored the adaptive significance of pendulous flowers during anthesis in these two Anisodus species, and upward fruits with persistent calyx in A. luridus. The major findings of my investigations are summarized as follows: 1. Both fruit set and seed number from manual selfing and outcrossing did not differ significantly in the two species, showing that both A. luridus and A. carniolicoides were fully self-compatible. The low fruit set and seed production after pollinator isolation without emasculation indicated a potential ability of autonomous selfing in both species. Seed production with supplemental outcross pollen was greatly enhanced compared with natural flowers, suggesting pollen limitation in these two species. Vespula rufarufa L. and Dolichovespula saxonica Fabr. were the most frequent pollinators of A. luridus and A. carniolicoides, respectively. Based on the total number of pollen grains deposited on virgin stigmas within one day from 10:00 to 17:00 (7 h in total) to evaluate total pollination efficiency, I found that pollination efficiency of intact flowers was significantly higher than that of emasculated flowers in A. carniolicoides, but not in A. luridus. Therefore, visitations of D. saxonica to A. carniolicoides were speculated to result in selfing within flower, i.e. facilitated selfing, whereas V. rufarufa could facilitate outcrossing among flowers in A. luridus. Additionally, A. tanguticus (Maxim.) Pascher, the putatively primitive species in Anisodus, was reported to be self-incompatible/partial self-compatible and pollinated by bumblebees, ants and flies. Compared with the pollination mechanism of A. tanguticus, it was obvious that self-compatibility occurred in the derived species and the evolutionary transition from self-incompatibility to self-compatibility together with pollinator shift did happen during the speciation in this genus. Moreover, the unpredictable and frequent rain in alpine environment might depress pollinator activity, which could be the principal reason for pollen limitation in A. luridus and A. carniolicoides. 2. Flower stalks of A. luridus and A. carniolicoides bend during flowering, but erect when fruiting only in A. luridus, together with enlarged and persistent calyx. My results showed that (1) in the two Anisodus species, there was no significant difference in pollinator visitation frequency and pollination efficiency between pendulous and erected flowers in the field, so pendulous flowers were unlikely to attract more pollinators or enhance pollen deposition. (2) In artificially erected flowers, pollen grains in anthers greatly decreased after rain-wash in A. luridus and A. carniolicoides. Additionally, for A. luridus, pollen germination rate reduced significantly due to water immersion and direct exposure to sunlight, indicating that nodding flowers could maintain viability of pollen grains in front of rain immersion and intense solar radiation. (3) After supplemental pollination in A. luridus, the number of mature seeds, seed set and weight of 100 seeds from fruits without any water in persistent calyx were much lower compared with intact control fruits, but no significant difference existed in seed germination rate. I conclude that the reflexed flower stalk made the campanulate corolla in two Anisodus species act as an umbrella to avoid rain damage to pollen quantity and quality, protecting pollen grains from direct exposure to intense solar radiation and improving male fitness. The upright fruit pedicel in A. luridus could support the elongated persistent calyx to hold water inside when rainfall was frequent, providing a stable microenvironment for the fertilized ovules and then promote their development, thus enhance female fitness. Nodding flowers in the two species and upright fruits in A. luridus seem to be an effective strategy to adapt the typical alpine environment of the QTP, characterized by frequent and unpredictable rains, intense solar radiation in the daytime and chilling at night.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.kib.ac.cn/handle/151853/430
Appears in Collections:昆明植物所硕博研究生毕业学位论文_学位论文

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Recommended Citation:
铃铛子(Anisodus luridus)和赛莨菪(A. carniolicoides)的传粉机制与生态适应.王赟[d].中国科学院昆明植物研究所,2009.20-25
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