珍稀濒危植物小花木兰传粉生物学研究

基于定株观测，对小花木兰（Magnolia sieboldii）野生种群和人工栽培种的开花物候进行了研究。结果表明，小花木兰花期为5月中下旬至6月中下旬，花期20d左右，单花花期一般为5～7d，盛花期为6月1～5日；开花过程中花部表型变化明显，花粉在花开时不成熟，但雌蕊已经成熟，花开后雌蕊柄伸长，约20h后下柱头依然湿润，上柱头已萎缩变褐色，再过约40h下柱头也萎缩失去活力．此时花粉成熟，花药裂开；花的柱头接受到的花粉量由下往上依次减少。检测花粉活力、萌发率发现，小花木兰花粉在散发6d后基本失去活力和萌发能力。重力玻片法观测表明，小花木兰为虫媒传粉；花柱的授粉率不高，为65％；柱头上平均花粉量为3．5个；自然状态下结实率低，为13．5％，人工栽培为20．1％；外轮花被片全部去掉，结果率下降至11．3％；去掉雄蕊，结实率下降至10．7％；再辅以人工授粉，结果率上升至25．0％。小花木兰的访花昆虫种类较少，访花频率低，其中蜜蜂和一种蚜科（Aphididae）小昆虫对其传粉影响较大。同花期灯台附（Cornus controversa）等植物对其传粉产生昆虫竞争作用。环境因素如光照、温度、阴雨、海拔等均对其传粉产生一定影响。

Pollination biology of endangered Magnolia sieboldii

Bases on fixed plants observation, this paper studied the flowering phenology of wild and artificial Magnolia sieboldii populations. The results showed that the blooming time lasted about 20 days, from the middle and last the day of May to the middle and last of June. Full blooming time was from June 1 to 5, and the flower parts changed distinctly in blooming time. Pollens were not mature at beginning flowering, when the pistil had already matured, with pistil stem elongated. After about 20 hours, the stigmas which had already turned black at basal part were wet. After about another 40 hours, pollens turned to mature and anther became splitting. The stigmas at basal and middle parts of the receptacle received more pollens than those at the apical. Pollen lost vigor after 6 days, with 65 % of pollination rate. The mean number of per accepted pollen stigma was 3.5, and the rate of fruit set was 13.5 % under natural conditions, 20.1% in planting, 11.3 % as taking out the perianth, 10.7 % if there was no stamen, and 25.0 % in condition of pollination by manpower. The pollination efficiency passed by the insects of M. sieboldii was low because of fewer visiting insects and fewer visiting frequency. Bee and a species of Aphididae were the most effective pollinators. Comus controversa, whose flowering phase was the same as M. sieboldii, had a competition with the passing pollen insects. The insect-visiting rate was affected by several environment factors such as light, temperature, rain and altitude, and the visitation peak was different in different habitats and under different weather conditions. The brighter the sky was, the higher the visitation rate and visiting peak came earlier.