濒危植物安徽羽叶报春两种花型的繁育特性及其适应进化

二型花柱的维持机制和自然选择压力多年来一直是生态学和进化学研究领域的热点之一。通过实验室栽培和野外观察统计相结合的方法,对安徽羽叶报春两种花型(长柱花和短柱花)的形态特征、花粉活力、柱头可授性、花粉/胚珠比、自然授粉及结籽能力、自交亲和性等繁育特性进行了比较研究。结果表明:长、短柱花的花冠直径和裂片宽无明显差异,而花冠筒、雌蕊和雄蕊高、花粉数目及大小、P/O比均有显著差异。在自然条件下,长柱花所接受的总花粉数要明显高于短柱花的总花粉数,但所接受的异型花花粉数和平均每果结籽数两者无显著差异。长柱花和短柱花的花粉和柱头活力相似,均能在较长时间内维持较高活力,仅在开花末期显著下降。两种花型的花在自花授粉、同型异花授粉、异型花授粉条件下均能结籽,但异型花授粉的结籽数均明显高于自花授粉和同型异花授粉结籽数。在长柱花各种授粉方式中,花粉萌发率无明显差异,但异型花花粉管的生长速度明显比同型异花花粉和自花花粉的快,而在短柱花柱头上表现为异型花授粉的萌发率最高,但只要萌发后在花柱中的生长速度无显明差异。此外,综合上述结果,对二种花型花部综合征的维持机制及自然选择压力进行了探讨。

Reproductive characteristics and adaptive evolution of pin and thrum flowers in endangered species, Primula merrilliana

The mechanism for maintenance and evolution of the distylous syndrome has attracted wide attention among ecological and evolutionary researchers. The reproductive characteristics, such as the viability of pollens and of stigmas, the ratio of pollen grains and ovules per flower, the fecundity of pistils and their ability of receiving pollens under natural conditions, and self-compatibility levels, of pin and thrum flowers in Primula merrilliana Schltr. were comparatively investigated by experiments in greenhouse and surveys in wild populations. The studies of 13 wild populations indicated that the diameter of corolla and the width of corolla lobe were similar between pin and thrum morphs (P>0.05). The corolla tube length of thrum (short-styled) flower (7.33 mm) was significantly longer than that of pin (long-styled) flower (6.35 mm). In thrum morph, anther (7.30 mm high) was at the mouth of the corolla tube, and the stigma (3.98mm high) was situated near the middle of the tubular corolla. In pin morph, however, the stigma (6.50 mm high) was near the mouth of the corolla tube, and the anther (4.09mm high) was at the middle of the tube. The mean number of the pin pollen grains per flower was significantly higher than that of thrum, but the diameter of the former was distinctly smaller than that of the latter. No significant difference was observed in the number of ovule between the two morphs, so the ratio of pollen grains to ovule was obviously higher in pin morph than in thrum morph. Under natural conditions, total pollen deposition at long-styled stigma was significantly higher than at short-styled stigma, but the legitimate pollen grains number (from the opposite morph flower) and filled seeds per fruit were not different significantly between the two morphs. In the cultivated condition, the longevity of pin and thrum flower was similar (about 20-21days). The pollen viability and stigma receptivity of pin flower were also similar to those of thrum. Pollen and stigma of two types flower kept fairly high viability during both prophase and metaphase of flowering (about 16 days) and only reduced distinctly at the end of flowering. And this phenomenon was more obvious in the pollen viability of long-styled flower. The results of artificial pollination indicated that self-compatibility in both morphs were similar, and that inter-morph, intra-morph and self pollinated all could bring filled seeds, but the mean filled seeds per fruit of inter-morph pollinated was higher than that of self- and intra-morph pollinated. The tubes of legitimate pollens (from the opposite morph flower) grew faster than those of illegitimate pollens (from the same morph or self flower) in pin style, but similarly in thrum style. The germination percentage of legitimate pollens was higher than that of illegitimate pollens at thrum stigma, but no such pattern was found in plants with pin stigma. Based on the results above, the breeding system and the mechanism of maintenance of the distylous syndrome in P. merrilliana were discussed.