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裸果木是亚洲中部荒漠区少有的第三纪孑遗物种,也是构成石质荒漠植被群落的重要建群种之一,由于人为干扰,其自然种群处于不断衰退中。本文通过野外观察和人工授粉实验等方法,对裸果木的花部特征及繁育系统进行研究,对于揭示该物种生活史特征并探讨影响其生殖成功的因素及制定相应的保护和管理策略具有重要意义。结果表明:裸果木为两性花,花小,无花瓣,雄蕊10枚,外轮5枚雄蕊败育,胚珠1枚,开花盛期有少量花蜜并散发浓烈难闻气味,花粉活力和柱头可授性之间存在46 h的重叠期,且不完全雌性先熟,柱头和花药在多数花的单花花期结束时并未接触,因此,裸果木花主要表现为适应异花传粉的雌雄异位特征;花粉/胚珠比(P/O)为1371.67±236.21,异交系数(OCI)为3;不同花粉来源(自然授粉、自花授粉、同株异花和异株异花授粉)的花粉在柱头上均能萌发,但花粉管生长速度存在差异,同株异花授粉和异株异花授粉的花粉管生长速度较快,自花授粉的花粉管生长速度最慢且部分花粉管(43%)在到达子房时停止生长,并未到达胚珠;人工套袋实验的结果表明,裸果木不存在无融合生殖,自然结种子数低,自然授粉花的种子数远远低于人工异株异花授粉花,说明存在由于异花传粉者不足造成的传粉限制。裸果木部分雌性先熟和雌雄异位是两性花为避免雌雄功能重叠,促进异交而采取的一种花部机制,其繁育系统为兼性异交类型且需要传粉者,部分自交不亲和和传粉限制是影响该物种有性生殖成功的主要因素。
Naked fruit trees are rare Tertiary relic species in the desert area of central Asia and are also one of the important community groups that make up the stony desert vegetation community. Due to human interference, their natural populations are in decline. In this paper, field experiments and artificial pollination methods were used to study flower characteristics and breeding system of naked fruit trees, which is of great significance for revealing the life history characteristics of the species and discussing the factors that affect their reproductive success and formulating appropriate conservation and management strategies . The results showed that the bare fruit trees were bisexual flowers with small flowers and no petals. There were 10 stamens and 5 stamens absent in the outer ring, 1 ovule and few nectar in the flowering stage with strong bad smell, pollen viability and stigma receptivity There was a overlap period of 46 h, and the female was not completely premature. The stigma and anthers did not touch at the end of the flowering stage of most flowers. Therefore, the bare fruit was mainly characterized by heteroelement pollination. The pollen / ovule ratio (P / O) was 1371.67 ± 236.21 and the coefficient of heterosexuality (OCI) was 3. Pollens with different pollen sources (natural pollination, self pollination, homologous and heterotic cross pollination) Pollen tube grew faster but pollen tube grew more slowly with partial pollen tube (43%) than pollen tube The ovule was stopped when it reached the ovary and did not reach the ovule. The result of artificial bagging experiment showed that there was no apomixis in bare fruit, and the seed number in natural knot was low. The number of seeds in natural pollination was much lower than that in artificial allogeneic cross-pollination Flowers, indicating the existence of cross-pollination due to inadequate pollination restrictions. Parthenocarpic parthenocarpic and hermaphrodite are the flower mechanism of the two sexes in order to avoid the overlap of male and female functions and promote the outcrossing. The breeding system is facultative heterosexual type and needs pollinators, partial self-incompatibility And pollination restrictions are the main factors affecting the success of sexual reproduction of this species.