青篱柴通过促进亲和花粉生长而提高传粉精确性

异型花柱植物的适应意义在于提高亲和花粉的传递, 从而促进异交, 但是有不少研究发现柱头上落置了大量不亲和花粉。目前, 很少有人研究柱头是否有利于亲和花粉的萌发和花粉管伸长, 以及通过去雄处理排除花内和植株内不亲和花粉干扰从而验证二型花柱植物是否可以促进异交。本研究以亚麻科青篱柴属(Tirpitzia)的二型花柱植物青篱柴(T. sinensis)为研究对象, 分居群调查了青篱柴长、短柱型的植株数量, 测量不同柱型的花粉与柱头大小以及观察其表面纹饰, 测定不同开花时间长、短柱型的柱头活性与花粉活力, 统计自然状态下柱头上落置的不同表型花粉比例, 进一步统计花内、株内去雄和自然对照下柱头上落置的不同表型花粉比例, 计算型间、型内和混合授粉花粉管长度和花粉萌发率, 人工授粉检测其是否型内异交不亲和与自交不亲和。结果表明, 自然居群中长、短柱型青篱柴植株数量没有显著性差异; 短柱型青篱柴花粉体积显著大于长柱型, 且二者花粉表面纹饰不同, 但不同柱型的柱头表面积与表面纹饰无差异; 青篱柴开花第一天的花粉活力显著高于开花第二天, 而柱头活性在开花前两天无显著性差异; 自然状态下柱头上落置的不亲和花粉比例显著高于亲和花粉; 在长柱型青篱柴中, 花内和株内去雄显著提高了柱头上亲和花粉的落置比例; 柱头上授型内花粉, 其花粉萌发率和花粉管的长度都显著低于授型间花粉; 授粉结果表明青篱柴为型内异交不亲和与自交不亲和。二型花柱植物通过促进亲和花粉的萌发和花粉管的伸长而有利于型间授粉, 从而显著提高其传粉精确性。

Tirpitzia sinensis improves pollination accuracy by promoting the compatible pollen growth

Aims: The adaptive significance of heterostyly is to improve the transfer of compatible pollen, so as to promote outcrossing. Nevertheless, many studies have found that a large number of incompatible pollens are deposited on the stigmas. At present, few studies have focused on whether the stigmas promote the compatible pollen germination and pollen tube elongation and provide evidences for the pollination accuracy hypothesis by emasculating intraflower and intraplant pollen. Methods: Tirpitzia sinensis (Linaceae) was taken as materials, and the number of long-styled morph (L-morph) and short-styled morph (S-morph) of T. sinensis were investigated in the separate populations. The pollens and stigmas size of different morphs were measured and their surface ornamentations were observed. The viability of stigma and pollen of different flowering phases were measured. The percentage of different phenotypic pollens on the stigma were calculated. The percentage of compatible and incompatible pollens on the stigma were further calculated under intraflower, intraplant emasculation and natural control treatments. The pollen tube length and pollen germination rate of inter-morph, intra-morph and mixture pollination were measured. The heteromorphic self-incompatibility system was detected by artificial pollination treatments. Results: There was no significant difference in the number of L-morph and S-morph of T. sinensis in the natural populations. The pollen volume of S-morph was significantly larger than that of L-morph, and the pollen surface ornamentations of the two morphs were different, but there were no significant different in the stigma surface areas and surface ornamentations of the two morphs. The pollen viability of the first flowering day was significantly higher than that of the second day, while the stigma viability had no significant difference in the first and second day of flowering. The percentage of incompatible pollen on stigma was significantly higher than that of compatible pollen in natural state. The intraflower and intraplant emasculation treatments significantly increased the percentage of compatible pollen deposition compared with the natural control in the L-morph of T. sinensis. Compared with inter-morph pollination treatment, the intra-morph pollination treatment could significantly reduce pollen germination rate and pollen tube length. Pollination treatments showed that T. sinensis was self- and intramorphic pollination incompatible. Conclusions: These results indicate that the distyly improves pollination accuracy by promoting the compatible pollen germination and pollen tube elongation.