异型花柱是一种受遗传因素控制的花型多态性现象, 包括二型花柱和三型花柱两种类型。本文以茜草科艳丽耳草(Hedyotis pulcherrima)为实验材料, 通过对其野外居群的花型、花部形态及花粉特征等观察, 发现艳丽耳草野外居群同时存在长花柱型花和短花柱型花, 长/短花柱型花的数量比例为1:1。两型花具有精确的交互式雌雄异位特征, 并且该特征与花冠长度相关性显著。长/短花柱型花的柱头裂片长度、花粉大小及淀粉含量等具有二型性。花粉体外培养时花粉萌发率及花粉管生长速率无显著性差异。人工授粉后, 艳丽耳草长/短花柱型花型间异交花粉管生长形态正常, 授粉24 h后花粉管均已进入子房。而长/短花柱型花在自交及型内异交下均表现为不亲和, 花粉管生长停止于柱头, 花粉管顶端累积胼胝质并膨大。艳丽耳草没有无融合生殖现象, 型间人工辅助异交授粉结实率为100%, 显著高于自然结实率。本研究结果表明, 艳丽耳草是典型的二型花柱植物, 并具有异型自交不亲和 系统。

Heterostyly is a genetically controlled floral polymorphism, which includes both distyly and tristyly. We investigated morph ratio, floral and pollen morphology, and self-incompatibility of Hedyotis pulcherrima. Overall, the natural population of H. pulcherrima was isoplethic, containing long-styled and short-styled morphs with an equilibrium 1:1 ratio. Long-styled and short-styled morph exhibited a precise reciprocal herkogamy, which was significantly correlated with corolla length. Stigma-lobe length, pollen size, and starch content in pollen grains were dimorphic in the two morphs of H. pulcherrima, whereas pollen germination and pollen tube growth in vitro were not significantly different between the two morphs. Artificial pollination revealed that pollen tube shape was normal in both morphs where pollen tubes reached the ovary 24 h after pollination. However, pollen tube growth was arrested in the stigma with the accumulation of callose in the swollen tips in two morphs with self and intramorph pollination, indicating strict heteromorphic self-incompatibility in H. pulcherrima. No fruit was produced in emasculated netted flowers, suggesting the absence of apomixis. Artificial intermorph pollination resulted in 100% of fruit set, significantly higher than those with open pollination. Our results indicate that H. pulcherrima is a typically distylous species with heteromorphic self-incompatibility.