鸟媒传粉植物红花芒毛苣苔花药合生强度及其传粉适应意义

Mechanical strength of anther connation and its pollination adaptation of the bird-pollinated Aeschynanthus moningeriae (Gesneriaceae)

摘要

为探究鸟媒传粉植物红花芒毛苣苔（Aeschynanthus moningeriae）合生花药的传粉适应意义，研究了海南五指山分布的红花芒毛苣苔种群开花生物学、合生花药的发育过程与力学特性及其对传粉过程的影响。结果表明：1）红花芒毛苣苔二强雄蕊的一长一短 2 对花药的顶端在花蕾期就已呈黏合状态，并在整个花期发育过程中保持合生状态；长、短雄蕊的合生花药最终分别形成约 180°（平行）和 115°（倒“V”型）的角度。2）短雄蕊的花药合生程度更大，合生力学强度在向上（F_向上=0.159±0.031）N、向下（F_向下=0.211±0.034）N 方向上都显著高于长雄蕊合生花药（F_向上=0.127±0.020 N，F_向下=0.117±0.018 N）。3）叉尾太阳鸟（Aethopyga latouchii）是其唯一有效传粉者，对红花芒毛苣苔红色花冠及裂片上的黑色条纹（蜜导）敏感；长雄蕊和短雄蕊的合生花药主要分别接触鸟的额头和鸟喙基部，在鸟类头部形成更大范围的花粉沉积区，从而提高了后续访花过程中柱头接受花粉的概率。由于访花时鸟喙基部的冲击力较大，短雄蕊更强的合生程度和强度可以保持花药合生状态，维持花药相对稳定的位置和促进花粉输出。

Abstract

Anther connation is an important floral trait that influences pollination accuracy and efficiency by altering anther arrangement and anther-stigma separation (herkogamy). The flowering biology, the mechanical properties of connate anthers, and the pollination process of Aeschynanthus moningeriae (Gesneriaceae) at Mt. Wuzhi in Hainan Island, China were examined to investigate the developmental pattern of anther connation and pollination adaptation in the bird-pollinatedA. moningeriae. The results showed that A. moningeriae is hermaphroditic, with didynamous stamens containing anthers in pairs from the bud stage and that anthers were coherent throughout the whole flowering period. The long anther pair ultimately formed an angle of approximately 180° (parallel) while the short anther pair grow at 115° (inverted V-shape). The short anther pair was connated with more fused part than the long anther pair. The mechanical strength of the short anther pair was F = (0.159 ± 0.031) N and F = (0.211 ± 0.034) N in the upward and downward directions respectively, which is significantly higher than that of the long anther pair [upward:F = (0.127 ± 0.020) N; downward: F = (0.117 ± 0.018) N]. The fork-tailed sunbird (Aethopyga latouchii) was the only effective pollinator. The red corolla, along with the black stripes on the lobes, function as a nectar guide. The long anther pair was mainly touched by the bird forehead, while the short anther pair was contacted mainly by the narrow base of the bird beak. Such separated pollen deposition increased the contact probobality of the stigma with pollen. Because the bird beak exerted stronger force on anthers, the higher mechanical strength with higher fusion proportion of the short anther pair can thus maintain at a fusion mode and spatial position of the connate anthers under stronger force, increasing pollen removal ratio.

关键词

苦苣苔科 / 二强雄蕊 / 雄蕊发育 / 雌雄异位 / 雌雄异熟 / 传粉机制

Key words

Gesneriaceae / didynamous stamens / stamen developmentl / herkogamy / dichogamy / pollination mechanism

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基金资助

国家自然科学基金项目(42371054)

海南省科技厅重大研发项目(ZDYF2023RDYL01)