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湿地植物大花百合种群的性系统特征

花匠小妙招
2024-11-17 05:42

摘要：

开花植物性系统特征是植物在长期适应进化过程中逐渐形成的繁殖策略, 它在一定程度上影响了物种的种群结构及其在生境中的分布格局, 因此性系统特征一直是植物进化与生态学领域的研究热点。本研究于2012年和2020年在吉林省金川泥炭沼泽湿地, 通过样地调查取样的方法, 研究了湿地植物大花百合(Lilium concolor var. megalanthum)的性系统特征以及不同性别表型植株的比例、密度及空间分布格局, 并探究了大花百合植株个体大小和其性别表达的联系, 比较了不同性别表型的花粉实际可育性和来源不同的花粉授粉处理结实后的种子活力。结果显示, 个体水平上, 大花百合具有雄花植株、两性花植株和雄花两性花同株(即雄全同株) 3种性表型; 种群水平上, 具有雄花的个体充当父本, 通过花粉向下一代传递基因, 而具有两性花的个体主要充当母本, 通过胚珠实现基因的传递。2020年大花百合雄花植株占种群内开花植株的39.14%, 相比2012年雄花植株比例增加了22.80%; 大花百合种群分布密度为0.06株/m2, 较2012年下降了0.09株/m2。从2012年到2020年, 总体表现为种群密度降低, 雄花植株相对比例增加的趋势。两性花植株和雄花植株在小尺度范围主要呈聚集分布, 随着尺度增大, 趋于随机分布。雄花植株显著小于两性花植株, 但鳞茎资源分配显著高于两性花植株。大花百合植株的性表达遵循大小依赖的性分配假说: 个体较小的植株表达为雄花植株, 而个体较大的植株则为两性花植株或雄全同株。在不同授粉处理下的结籽率和种子萌发结果表明, 大花百合自花授粉结籽率和坐果率显著低于异花授粉, 雄花植株和两性花植株花粉可育性以及对两性花植株授粉后所获得种子活力无显著差异。大花百合雄花植株的出现可能是对有限环境资源条件适应的结果, 反映了湿地条件下该植物在生长和繁殖资源之间的权衡策略, 在长期的湿地演变过程中, 这种性系统特征的出现具有一定的适应性意义。

关键词: 大花百合, 个体大小依赖, 性表达, 花粉可育性, 种子活力

Abstract

Aims The sexual system characteristics of flowering plant is a reproductive strategy gradually formed during the process of long-term adaptation and evolution, which affect the population structure of plant and its distribution pattern to a certain extent. Therefore, sexual system characteristics have always been a hot topic in the field of plant evolution and ecology.
Methods In this study, a survey was conducted to determine the sexual system characteristics and the proportion, density and spatial distribution pattern of Lilium concolorvar. megalanthum with different sexual phenotypes, and to explore the relationship between individual plant size and sexual expression in Jinchuan peatland of Jilin Province in 2012 and 2020. We compared the actual pollen fertility with different sexual phenotypes and the seed viability after pollination treatment with different pollination sources.
Results The results showed that at the plant level L. concolor var. megalanthum has three sexual phenotypes: male flower, hermaphrodite flower, and andromonoecy. At the population level, the plants with male flower act as male parents and transmit genes to the next generation through pollens, while the plants with hermaphrodite flower mainly act as female parents and transmit genes through ovules. The plant with male flower accounted for 39.14% of flowering plants in the population in 2020, which increased by 22.80% compared with the proportion in 2012. The population density of L. concolor var. megalanthum was 0.06 plants/m2in 2020, which was 0.09 plants/m2lower than that in 2012. Compared with 2012, the population density decreased and the relative proportion of plants with male flowers increased in 2020. Hermaphroditic and male flower plants mainly showed aggregated distribution in small scale, and tended to random distribution with the increase of scale. The plants with male flower are significantly smaller than plants with hermaphrodite flower, but the resource allocation of bulb is significantly higher than that of the plant with hermaphrodite flower. The sexual expression of L. concolor var. megalanthumfollowed the hypothesis of size- dependent sexual allocation. The smaller plant produces only one male flower, while the larger plant produces hermaphroditic flower or are andromonoecious. The results of seed set and germination of different pollination treatments showed that the seed set and fruit set of self-pollination are significantly lower than those of cross-pollination. There was no significant difference in pollen fertility between male and hermaphroditic flower plant. There was also no significant difference in seed viability pollinated by pollen from male and hermaphroditic flower plant.
Conclusion The appearance of male flower may be the result of L. concolor var. megalanthum adaptation to limited environmental resources, and it reflects the trade-off strategy between growth and reproduction of this plant under the stressful condition in peatland. The emergence of this sexual system has a certain adaptive significance for L. concolor var. megalanthum with the long-term peatland succession.

Key words: Lilium concolor var. megalanthum, size-dependent, sexual expression, pollen fertility, seed viability