Programa de Pós-Graduação em Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.
Instituto de Biologia, Universidade Federal de Uberlândia, Uberlândia, Minas Gerais, Brazil.
Plant Biol (Stuttg). 2024 Jun;26(4):612-620. doi: 10.1111/plb.13649. Epub 2024 Apr 18.
Most Aristolochiaceae species studied so far are from temperate regions, bearing self-compatible protogynous trap flowers. Although self-incompatibility has been suggested for tropical species, the causes of self-sterility in this family remain unknown. To fill this gap, we studied the pollination of the tropical Aristolochia esperanzae, including the physical and physiological anti-selfing mechanisms. Floral visitors trapped inside flowers were collected to determine the pollinators. Protogyny was characterized by observing the temporal expression of sexual phases and stigmatic receptivity tests. The breeding system was investigated using hand-pollination treatments. Pollen tube growth was observed using epifluorescence to identify the self-incompatibility mechanism. Flies were the most frequent visitors found inside A. esperanzae trap flowers, with individuals from the family Ulidiidae being potential pollinators since they carried pollen. The characteristic flower odour and presence of larvae indicate that A. esperanzae deceives flies through oviposition-site mimicry. Although this species showed incomplete protogyny, stigmatic receptivity decreased during the male phase, avoiding self-pollination. Fruits developed only after cross- and open pollination, indicating that the population is non-autonomous, non-apomictic, and self-sterile. This occurred through a delay in the growth of geitonogamous pollen tubes to the ovary and lower ovule penetration, indicating a late-acting self-incompatibility mechanism. Our findings expand the number of families in which late-acting self-incompatibility has been reported, demonstrating that it is more widespread than previously thought, especially when considering less-studied tropical species among the basal angiosperms.
迄今为止，大多数研究的马兜铃科物种都来自温带地区，具有自交亲和的延迟型陷阱花。尽管已经提出了热带物种的自交不亲和性，但该科的自育性原因仍不清楚。为了填补这一空白，我们研究了热带马兜铃科植物 A. esperanzae 的传粉，包括物理和生理的抗自交机制。收集被困在花朵内的访花者以确定传粉者。通过观察性相的时间表达和柱头可接受性测试来描述原雌同熟。通过人工授粉处理来研究繁殖系统。使用荧光显微镜观察花粉管生长以确定自交不亲和机制。蝇类是在 A. esperanzae 陷阱花内发现的最常见访客，来自 Ulidiidae 科的个体是潜在的传粉者，因为它们携带花粉。特征性的花香味和幼虫的存在表明 A. esperanzae 通过产卵位点模拟来欺骗蝇类。尽管该物种表现出不完全的原雌同熟，但柱头可接受性在雄性阶段下降，避免了自交。只有在异交和开放授粉后才会发育果实，表明该种群是非自主的、非无融合生殖的和自育不育的。这是通过延迟异交花粉管向子房的生长和降低珠孔穿透来实现的，表明存在迟发型自交不亲和机制。我们的发现扩大了迟发型自交不亲和性报告的科数，表明它比以前认为的更为普遍，尤其是在考虑到在基础被子植物中研究较少的热带物种时。
