同域分布柽柳属两种植物的传粉生物学研究

Pollination characteristics of two sympatrically distributed Tamarix species in south Xinjiang,China

以同域分布于新疆南部的早春开花植物短穗柽柳(Tamarix laxa Willd)和紫杆柽柳(T.androssowii Litw)为材料,对它们的开花式样、花部特征、花报酬特点、传粉特性及交配方式进行比较研究。结果表明,2种植物居群和个体水平的花期及单花寿命间存在显著差异;紫杆柽柳的居群花期比短穗柽柳短,而短穗柽柳个体花期和单花寿命比紫杆柽柳长。2种柽柳的花瓣、雌雄蕊长度、花粉胚珠数及花粉/胚珠比值(P/O)间也存在显著差异。二者的花瓣、雌雄蕊均能分泌香味,访花频率与花蜜量均存在正相关。主要传粉者在短穗柽柳上的访花频率和沉积花粉效率高于紫杆柽柳,且存在显著差异。2种植物通过自花和异花授粉均可结实,属于混合交配系统;二者的自交不亲和指数及花粉限制程度间存在显著差异;紫杆柽柳的自交亲和性高于短穗柽柳,而短穗柽柳的花粉限制指数高于紫杆柽柳。因此,2种柽柳的开花式样、花部特征及花报酬的差异,是它们在传粉者受限的早春环境中为吸引更多的访花昆虫、提高雌性繁殖率所形成的繁殖对策。

Tamarix laxa Willd and T. androssowii Litw are two early spring flowering plants,which are widely and sympatrically distributed in south Xinjiang,China. A comparative study of flowering characters,floral rewards,pollination characters,and mating mode in T. laxa and T.androssowii was undertaken in the same natural population. We aimed to explore the effect of floral syndrome on pollination characteristics. Population-and individual-level flowering time and floral longevity were significantly different between species（ P〈0.01）; the populationlevel flowering time of T. laxa was longer than that of T. androssowii,but individual-level flowering time and floral longevity of T. androssowii was longer than that of T. laxa. The lengths of each floral parameter（ petals,stamens,and pistils） and numbers of pollen and ovules were significantly different between species. Petals,stamens,and pistils were fragrant andnectar volume was significantly positively correlated with pollinator visiting frequency. Visiting frequency and pollen deposited on the stigma by the major pollinator were significantly different between species,and were higher in T. androssowii than in T. laxa. Flowers produced fruits after self-pollination and cross-pollination; thus,they exhibited a mixed mating system.There were significant differences between the self-incompatibility and pollen limitation index in both species. The self-incompatibility index was higher in T. androssowii than in T. laxa,but pollen limitation was higher in T. laxa than in T. androssowii. Thus,both species exhibited pollen limitation due to low pollinator activity.