Flowers of Meliaceae are traditionally described as bisexual, but functionally unisexual flowers have been reported for many genera. For Trichilia, several reproductive systems have been previously reported: subdioecy, gynodioecy, polygamy and hermaphroditism. The aim of this study was to analyze the occurrence of floral dimorphism and sexual-functional aspects of the flower of Trichilia claussenii. Structural and developmental analyses of flowers of Trichilia claussenii were performed using light and electron microscopy. In addition, male and female function of flowers was investigated through pollen viability and stigma receptivity tests, hand pollination and seed germination. Two floral morphotypes were identified in Trichilia claussenii: one morphologically male with a reduced gynoecium and the other morphologically female with anthers which do not release pollen. In the supposedly male flower, anthers are well developed and produce viable pollen grains. A conspicuous nectary disk differentiates at the base of the gynoecium, and the ovary has small ovules; however, our study proved that this ovary develops into a fruit, which contains viable seeds. In contrast, the supposedly female flower has larger gynoecium and ovules, and the nectary is smaller and inconspicuous. The stamens of female flowers have inviable pollen grains due to a tapetal necrotic product that keeps them united into an amorphous mass within the anthers. Male flowers are geitonogamous. Our results demonstrate that Trichilia claussenii exhibits subtle sexual floral dimorphism with female flowers and bisexual flowers distributed in different individuals. Our results indicate that male sterility occurs in only one morphotype; therefore, the species is gynodioecious.

楝科的花传统上被描述为双性花，但已经报道了许多属的功能性单性花。对于Trichilia，以前曾报道过几种生殖系统：亚雌雄同体、雌雄同体、一夫多妻和雌雄同体。本研究的目的是分析Trichilia claussenii花的花二形性和性功能方面的发生。使用光学和电子显微镜对Trichilia claussenii的花进行结构和发育分析。此外，通过花粉活力和柱头可受性试验、人工授粉和种子萌发研究了花的雄性和雌性功能。在Trichilia claussenii中鉴定出两种花的形态型：一个形态上雄性，雌蕊减少，另一个形态上雌性，花药不释放花粉。在所谓的雄花中，花药发育良好并产生有活力的花粉粒。雌蕊群基部有明显的蜜腺盘，子房有小胚珠；然而，我们的研究证明，这个子房发育成果实，其中包含有活力的种子。相比之下，雌花的雌蕊和胚珠较大，蜜腺较小且不显眼。由于绒毡层坏死产物使雌花的雄蕊具有不可存活的花粉粒，使它们在花药内结合成无定形团块。雄花是雌雄同体的。我们的结果表明，Trichilia claussenii雌花和两性花分布在不同个体中，表现出微妙的两性花异形性。我们的结果表明雄性不育只发生在一种形态型中；因此，该物种是雌雄同株的。