狭叶坡垒传粉生物学初探

Pollination biology of Hopea chinensis

关键词:  狭叶坡垒, 繁育系统, 传粉生物学, 花气味, 蕈蚊

Key words:   Hopea chinensis, breeding system, pollination biology, flower odor, fungus gnat

摘要:

狭叶坡垒(Hopea chinensis)为常绿乔木,是我国热带季雨林的代表树种之一。它树型优美,具一定的耐寒性,是我国珍稀濒危保护植物。为阐明其传粉生物学特征和迁地保护的繁殖潜力,该文在引种地桂林植物园对狭叶坡垒的开花物候、花尺寸和花气味进行了观察和测量,运用杂交指数(OCI)、花粉胚珠比(P/O)、花粉活力、柱头活性检测和人工自交等方法对其繁育系统进行了检测,观察了访花昆虫并检验了其传粉效率,通过人工异交检验了繁殖潜力和可能的传粉限制。结果表明:(1)桂林植物园内狭叶坡垒的花期为7月底到9月底,持续60 d左右,一个花序花期约12 d,单花期约3 d,花朵开放时间为17:00—18:45。(2)雌雄同熟,雌蕊空间位置高于雄蕊,高花粉活力和高柱头可授性出现时间基本一致。(3)OCI 等于4,P/O为10 788±984。(4)无自动自花授粉能力且自交不亲和,自然条件下和异交授粉能坐果且坐果率无显著差异。(5)蕈蚊是狭叶坡垒唯一的传粉者。(6)主要花香成分为β-榄香烯、(E)-7,11-二甲基-3-亚甲基-1,6,10-十二碳三烯和1-石竹烯。综上所述,狭叶坡垒繁育系统为异交,在迁地保护地需要蕈蚊作为传粉者,能坐果并得到成熟种子,不存在授粉限制。

Abstract:

Hopea chinensis is one of the representative tree species of tropical seasonal rainforests in China. It is an endangered and protected plant with beautiful tree shape and cold tolerance. To clarify its pollination biology, and breeding system and demonstrate its reproductive potential in Guilin, where this species was introduced for protection, we conducted the following experiments: the observation of flowering phenology, the measurement of floral size and scent, the estimation of the breeding system by out-crossing index(OCI), the pollen-ovule ratio(P/O), pollen viability and the stigma receptivity and self-pollination, the observation of pollinators and the test of their pollination effectiveness, the assessment of reproductive potential and pollination limitation by hand cross-pollination. The results were as follows:(1)The flowering season of H. chinensis in Guilin Botanical Garden is from the end of July to the end of September. It lasts about 60 d. An inflorescence flowers for about 12 d, and the anthesis of a single flower lasts about 3 d. The flowers begin opening from 17:00 to 18:45.(2)H. chinensis is not dichogamous but herkogamous with stigmas higher than anthers. The period of high pollen vigor and that of high stigma receptivity largely coincide.(3)The outcrossing index(OCI)was four and pollen/ovule ratio(P/O)was 10 788±984.(4)Neither flowers self-pollinated nor thoses bagged all the tome set any fruitse, fruit set did not differ significantly between natural pollination and hand cross-pollination.(5)Fungus gnats were the only flower visitor to the H. chinensis in Guilin Botanical Garden and flowers set no fruits with fungus gnat excluded.(6)The floral scent is dominated by β-elemene,(E)-7,11-dimethyl-3-methylene-1,6,10-dodecatriene and 1-caryophyllene. In conclusion, H. chinensis breeding system is self-incompatible, and it relies on fungus gnats for fruit production. It can set fruits and produce mature seeds in Guilin. The results can promote the protection and propagation of H. chinensis.