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花序内性别表达和性别分配的差异在被子植物中非常普遍。常见的变化模式是:在顺次开放的花序内,从早开的花到晚开的花,生殖结构大小和数量依次减少,晚开的花偏向雄性。通常认为资源竞争和位置效应是形成这种差异的主要原因。在喜树(Camptotheca acuminata)的聚伞花序内,早开的头状花序在花序直径、小花直径、短雄蕊长度、坐果率、果序重量等方面与晚开的头状花序差异显著。通过去除喜树聚伞花序一级或一级和二级头状花序来控制花序内的资源分配,从而分析影响喜树花序内花性状、性别分配及生殖能力的主要因子。结果显示,去除部分头状花序后,剩余头状花序的花序直径、小花直径明显增加,短雄蕊长度明显缩短,位置间差异消失;而坐果率、果序重量的位置间差异依然显著。表明资源限制对花序直径、小花直径和短雄蕊长度等影响显著,而坐果率和果序重量受位置效应影响明显。喜树雄全同株的性别分配可能是对特定生殖状况和资源状况适应的结果。
Differences in gender expression and gender distribution in inflorescences are very common in angiosperms. The common pattern of change is that in the orderly open inflorescences, the size and number of reproductive structures decrease in turn from the early open flowers to late open flowers, and late open flowers tend to be male. Resource competition and location effects are generally considered the main reason for this difference. In the camptotheca acuminata cymes, the early open flower heads showed significant difference from late opening flower heads in terms of inflorescence diameter, flower diameter, short stamen length, fruit setting rate and fruit weight. The allocation of resources within the inflorescence was controlled by removing the first-, first- and second-grade flower heads of the camptotheca acuminatum to analyze the major factors affecting flower traits, gender distribution and reproductive capacity in the cambium. The results showed that after removing some of the flower heads, the diameter of inflorescences and flower diameter of the remaining flower heads were significantly increased, the length of the short stamens was shortened, and the differences between the positions disappeared. However, the differences in fruit setting rate and fruit weight were still significant. The results showed that the resource limitation had significant effects on the diameter of inflorescence, the diameter of floret and the length of short stamens, while the fruit setting rate and fruit weight were significantly affected by the position effect. Gender distribution in the same strain of Camptotheca acuminata may be the result of adaptation to particular reproductive and resource conditions.