Abstract: Aims Nyphaea candida C. Presl, an endangered species endemic to Xinjiang and classified as a National Class II protected plant, faces high risks of extinction and requires urgent conservation efforts. The aim of this study is to reveal its reproductive characteristics and explore factors associated with endangered status from a reproductive biology perspective. Methods This study systematically investigated the flowering phenology, floral morphology, breeding sys-tem, pollination process, and seed germination characteristics of N. candida in natural populations. Important findings The flowering period lasts from May to September, with a single flower lifespan of ap-proximately four days, while the stigma remains receptive for only 1～2 days. Pollinators are mainly syrphid flies, though visitation frequency is low and easily affected by adverse weather conditions such as rain. Ex-perimental data suggest that N. candida follows a mixed mating system, predominantly outcrossing but also self-compatible, and depends on pollinators for successful reproduction. Seed viability is measured at 45.33±4.29%, yet germination rate under natural conditions is low (only 2.67±1.63%), restricted by seed coat barriers. The reproductive process of N. candida faces significant limitations due to its floral characteristics, pollination behavior, and seed germination challenges, notably with limited pollinator availability, low visita-tion frequency, and reduced seed viability. Environmental factors (e.g., rainy weather) further inhibit pollina-tion success, imposing substantial pollination constraints on this species. In unstable pollination environments, N. candida tends to adopt a spontaneous self-pollination strategy, which may lead to inbreeding depression and further increase its risk of endangerment.

Key words: Endangered species, Nymphaea candida, flowering phenology, breeding system, pollination, seed germination, endangerment factors