濒危植物丰都车前的繁育系统与传粉生物学研究

Breeding system and pollination biology of endangered Plantago fengdouensis

丰都车前为三峡库区特有珍稀濒危植物,目前仅在重庆市江津支坪镇涂家村附近大中坝上有一小种群分布。以野生种群和移栽种群为对象,通过野外观察和人工授粉实验对丰都车前传粉生物学及繁育系统进行研究。结果表明:(1)丰都车前单花花期约4 d,花序花期约8 d,种群花期约3个月;单花开花进程可分为6个时期:花蕾期、雌蕊伸长期、雄蕊初露期、花瓣展开期、花瓣反折期、枯萎凋谢期。(2)花瓣展开前,柱头先伸出花冠,达最高可受性,之后花瓣展开雄蕊才露出,而此时大部分柱头已枯萎失活丧失可受性,只有少部分具可受性。表现出雌雄异熟的特征,一定程度避免了自交的发生。(3)花粉活力始于雄蕊初露期,花瓣展开、花药开裂时花粉活力最高,至枯萎凋谢前均具有活力。花粉活力最高期避开了柱头可受性最佳期,仅有少部分重叠。(4)繁育系统检测显示,花粉/胚珠比为15373.29,杂交指数为3。结合套袋实验表明,丰都车前可能同时具有风媒和虫媒传粉机制,传粉昆虫为中华蜜蜂、食蚜蝇,但数量偏少,不存在无融合生殖,异交为主,部分自交亲和,有时需要传粉者。(5)开花时期避开了其分布地洪水淹没期,能够顺利完成开花授粉及座果。综上所述,丰都车前的花部特征、开花物候和繁育系统为适应分布地夏季洪水水淹胁迫提供了一定的生殖保障,促进了该种群的续存。

Plantago fengdouensis is an herbaceous member of the Plantaginaceae. It has a two-year lifecycle, and is a unique and endangered plant in the Three Gorges reservoir area where it is currently only found on the dam near Tujia Village, Zhi Ping Town, Jiangjin, Chongqing, China. Therefore, it only has a small population distribution. The pollination biology and breeding system of Plantago fengdouensis were studied using field observations and an artificial pollination experiment that included both wild and transplanted populations. The results showed that the flowering span of a single flower, the inflorescence, and the population were about 4 d, 8 d, and 3 months, respectively. The single flower flowering process is divided into six stages. These are the bud stage, pistil elongation stage, early stamen showing stage, petal expansion stage, petal reversal stage, and the flower withering stage. Before the petals unfold, the stigmas first emerge from the corolla and, reach their highest receptivity. The stamens are exposed after the petals have unfolded, but at this point, most of the stigmas have withered, are inactive, and have mainly lost their receptivity. Only a small number are receptive at this point. This dichogamy means that the plant, to a certain extent, avoids self-pollination. Pollen vitality begins at the early stamen showing stage, and they achieve their maximum vitality after the petals have unfolded. Then the anthers undergo dehiscence, but pollen vitality is maintained until the flower withering stage. The maximum pollen vitality period avoids the best time for stigma receptivity. However, there is a certain degree of overlap between the two stages. A study of the breeding system indicated that the pollen-ovule ratio was about 15373.29, and the hybridization index （OCI） was three. These observations, along with the bagging experiment, showed that the plant is adapted to both wind and insect pollination. The pollination insects are Apis cerana and Episyrphus sp., but bee numbers are lower than normal. In the breeding system of this species, out-crossing predominates and, although partially self-compatible, it requires pollinators. No fusion reproduction was observed. The flowering period avoids the flooding period in the area, which means the plant can successfully complete pollination and fruit setting. In summary, the floral characteristics, flowering phenology, and breeding system of Plantago fengdouensis provide some reproductive assurance of its ability to adapt to flooding stress in summer, which ensures the persistence of the population.