蛛网萼开花物候、花部特征及繁育系统研究

为探讨蛛网萼(Platycrater arguta)传粉生物学特性,该研究以江西上饶广丰铜钹山国家级自然保护区、江西阳际峰国家级自然保护区蛛网萼为材料,采用野外观察和人工授粉等方法,对蛛网萼开花物候、花部形态及繁育系统进行了研究。结果表明:(1)蛛网萼为伞形花序,种群花期一般在6月中下旬至8月中旬,单花花期为2~3 d,花序花期持续10 d。两个保护区由于年均温度与光照的不同,花期进程有显著不同。(2)蛛网萼可孕花与不孕花从绿色变为白色时对访花昆虫有吸引作用,不孕花能够增加昆虫的访花频率。(3)蛛网萼花粉胚珠比(P/O)为2 520~3 100,杂交指数即是3或4。(4)繁育体系属于以异交为主,部分自交亲和,需要传粉者;熊蜂(Bombus sp.)、四条蜂(Apis florea)和油茶地蜂(Andrena cammelia)是蛛网萼的有效传粉昆虫。(5)套袋和人工授粉结果显示,蛛网萼为兼性自交和异交授粉,异株异花授粉能显著提高坐果率及结籽率,这主要与生境中有效传粉昆虫种类、数量少,花粉传递效率低,种群间基因流交流降低以及柱头自花及同株异花传粉等有关,从而表明在蛛网萼现有生境中植株的早期生殖成功受到影响。蛛网萼种群分布范围扩张以有性繁殖为主,无性繁殖作为重要补充及繁殖保障。

Flowering phenology, floral traits and breeding system of Platycrater arguta

To study the pollination biology of Platycrater arguta, we conducted field observations and artificial pollination experiments on flowering phenology, morphology and breeding system. P. arguta studied in this paper was grown in Shangrao Guangfeng Tongbo Mountain National Nature Reserve and Yangjifeng National Nature Reserve in Jiangxi. The results were as follows:(1)P. arguta inflorescence as umbel, and flowering in middle summer, the flowering span of the population and single flowering were approximately 10 d and 2-3 d, respectively. The flowering process had significant difference due to the average annual temperature and illumination in two protected areas.(2)Fertile flowers and sterile flowers changed their colours from green to white to attract pollinators, and increased frequency of insect visiting.(3)The ratio of pollen to ovule(P/O)was 2 520-3 100. The outcrossing index(OCI)was 3 or 4.(4)The breeding system mainly belonged to outcrossing, with partial self-compatibility, and the pollinator insects were essential. The most frequent floral visitors were bees(Bombus sp., Apis florea and Andrena cammelia).(5)Two experiments bagged and artificial pollination showed that P. arguta breeding system could be self-pollination and cross-pollination, the fruit-setting rate and seed-setting rate of cross-pollination were significantly higher than self-pollination. Lack of pollination insects, low pollination efficiency, deposition of self pollen and partial self-compatibility may account for the low fruit set and seed set. It was suggested that habitat affected the early stage reproduction process of P. arguta plants. It was concluded that the main way of population spreading of P. arguta was the sexual reproduction and the asexual reproduction as an important supplementmean and reproductive protection.