Abstract:Effective conservation strategies require an understanding of the reproductive characteristics of plants. In this study, the reproductive biology of Cymbidium aloifolium was investigated in Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences in 2022 and 2023. The flowering phenology, breeding system, flower morphological characteristics, pollination characteristics and flower volatile components were examined. Our results showed that C. aloifolium flowers began to bloom during mid-April. An individual flower and the population of C. aloifolium lasted seven days and 36 days, respectively. The pollen viability was 47.15% at the beginning of anthesis but clearly decreased thereafter. The stigma remained receptive during anthesis, reaching its peak on the second day. The hand pollination experiment suggested that C. aloifolium was self-compatible but had no apomixes and spontaneous autogamy, and its breeding system was facultative xenogamy and insect pollinator-dependent. Fruit set under open pollination was low (6.9%). There were conical and finger-like protrusions on the epidermal cells at the apex and base of the labellum. Lipid granules were observed on the finger-like protrusions located at the base of the labellum and it is possible that those may be served as rewards for pollinators as reported for this orchid before. The anther cap was yellow in color with conical epidermal cells and it is thought that conical cells could reflect light and thereby attract pollinators. The only effective pollinator was Apis cerana. A significant amount of (E)-2-Decenyl acetate was detected in the floral volatile odor of C. aloifolium. Our results indicated that the floral characteristics of C. aloifolium might be highly adapted to pollinators, although direct evidence for this is lacking. This study of the reproductive biology of C. aloifolium will provide theoretical and practical guidance for ex situ conservation of rare and endangered orchid species in botanical gardens.
