绣球茜的二型花柱及其传粉生物学初步研究

Distyly and Pollination Biology of Dunnia sinensis(Rubiaceae)

首次对绣球茜(Dunnia sinensis Tutch)的花药和柱头高度、花粉和柱头形态,以及人工辅助授粉的结实情况等进行了研究。结果表明:绣球茜在同一居群中同时具有长花柱(Pin型)和短花柱(Thrum)两种花型,长花柱植株的柱头和雄蕊高分别为9.61±0.36 mm和6.79±0.38 mm,短花柱则为6.11±0.56 mm和8.96±0.59 mm,表现出互补式雌雄异位的花部特征。通过人工辅助授粉,两种花型植株的自交和同型植株间异交都不结实,仅在型间异交方能正常结实,说明绣球茜中存在极强的自交不亲和和型内不亲和现象。在花粉与柱头形态方面:长柱型花的单花花粉量(38555.6±6258.4)显著地小于短柱型花(52145.45±8924.5)(t=4.009,P<0.01),长柱花和短柱型花的胚珠数分别为38.73±1.85和39.1±2.25(t=-4.13,P>0.01);长柱型花花粉粒的大小(极径21.27±0.70μm)显著地小于短柱花(21.92±0.79μm)类型(t=3.890,P<0.01),而柱头乳突大小长柱类型要大于短柱类型,表现出明显的二型性。研究结果表明绣球茜是一种典型的二型花柱植物。此外,对其传粉昆虫及昆虫访花行为的观察表明,蝶类(青凤蝶属Graphium)和蜂类(熊蜂Bombus sp.和木蜂Xylocopa magnifica Smith)为绣球茜的主要访花昆虫和传粉昆虫,它们能够在两种不同花型植株之间有效地传粉。

The floral morphology, sexual system, and pollination biology of Dunnia sinensis Tutch. Were studied. The stigma and anther heights, morphology of pollen grains and stigma, as well as the fruit set after artificial pollination were evaluated. The results showed that individuals of D. sinensis within a population exhibited two floral morphs, viz., long-styled （pin） and short-styled （thrum） morphs. Stigma and anther heights in long-styled flowers are 9.61±0.36 mm and 6.79±0.38 ram, while in the short-styled flowers are 6.11±0.56 mm and 8.96± 0.59 mm respectively, exhibiting reciprocal herkogamy. No fruit was produced in treatments with self-pollination and intra-morph pollination, suggesting the occurrence of strong self and intra-morph incompatibility in the species. Ancillary dimorphisms were found in pollen and stigma of the two morphs： the pollen number in pin flowers is significantly smaller than in thrum flowers（38555.6± 6258.4 vs. 52145.45 ± 8924.5; t = 4.009, P 〈 0.01 ）, the pollen size of pins is also significantly smaller （21.27 ±0.70 p,m vs. 21.92± 0.79 ixm, t = 3.890, P 〈 0.01 ）, although the ovule numbers of the two morphs are similar （38.73± 1.85 vs. 39.1 vs 2.25, t =-4.13, P〉0.01, pin vs. thrum）; while the stigma papillae is larger in long-styled flowers than in short-styled flowers. It was concluded that D. sbnensis is a typically distylous species. Floral visitors and their behaviors were also observed, showing that bees （Bombus sp. and Xylocopa magnifica） and butterflies （Graphium sp.） were the main visitors and could efficiently pollinate between morphs in D. sinensis.