植物园迁地保护环境下纹瓣兰的繁殖生物学研究

Reproductive Biology of Cymbidium aloifolium (Orchidaceae) Under ex situ Conservation in a Botanical Garden

摘要:

深入了解濒危物种的繁殖特性，能为物种制定有效保护策略提供科学依据。该文于2022和2023年对中国科学院西双版纳热带植物园迁地保存的纹瓣兰 (Cymbidium aloifolium )的繁殖生物学特征进行了观察和研究，主要包括开花物候、繁育系统、花部形态特征、昆虫传粉特征以及花的挥发性成分等。结果表明：纹瓣兰的盛花期在4月中旬，单花花期为7 d；群体花期约为36 d。花粉活力在开花第1天时最高，约为47.15%，之后呈下降趋势。柱头在整个单花期一直具可授性，开花第2天可授性最强。人工授粉实验表明纹瓣兰自交亲和，不存在无融合生殖和自动自花授粉，繁育系统属于兼性异交繁育并依赖传粉者，自然结实率较低为6.9%。唇瓣的先端和基部的表皮细胞分别为锥形和指状突起，基部的指状突起细胞外附着有油脂颗粒，根据前人报道纹瓣兰的这些油脂颗粒可能是传粉者的报酬。药帽黄色，其表皮细胞为锥形细胞，能够反射光线，可能起到吸引昆虫的作用，中华蜜蜂 (Apis cerana) 是纹瓣兰唯一的有效传粉昆虫。纹瓣兰的挥发性气味中(E)-乙酸-2-癸烯-1-醇酯含量最高。研究结果表明纹瓣兰的花部结构与传粉昆虫具有显著的适应性。该文对纹瓣兰繁殖生物学的研究将为植物园迁地保护珍稀濒危兰花物种提供理论和实践指导。

关键词:迁地保护、纹瓣兰、花部特征、繁育系统、传粉特征、中华蜜蜂

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.

Key words:ex situ conservation; Cymbidium aloifolium; breeding system; Apis cerana cerana