Flower development of Meliosma (Sabiaceae): evidence for multiple origins of pentamery in the eudicots.
Flower development of Meliosma (Sabiaceae): evidence for multiple origins of pentamery in the eudicots.
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DOI：
10.3732/ajb.94.11.1828
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发表时间：
2007-11
影响因子：
3
通讯作者：
L. Wanntorp;L. P. Ronse De Craene
中科院分区：
文献类型：
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作者：
L. Wanntorp;L. P. Ronse De Craene
花发育研究是分子遗传学的补充，是了解被子植物花进化的重要工具。泡花树Meliosma veitchiorum、M. cuneifolia和M.利用扫描电子显微镜研究了小叶清风藤属（Sabiaceae）植物的花发育模式和形态，了解了花被分生现象的起源，并讨论了清风藤科在蔷薇科和真双子叶植物基级中的两个分类位置。泡花树属的花为五瓣，五个萼片中有两个，花瓣强烈退化，三个退化雄蕊与两个可育雄蕊交替，与小花瓣相对，雌蕊群为两心皮。泡花树的花发育呈螺旋状，无小苞片和萼片之分。由于这种发育，萼片，花瓣和雄蕊几乎是对生的，而不是像周期性的五瓣花那样交替。在四萼片花中，花瓣起始的方向相反。花的对称性似乎是横向左右对称的，尽管这被几乎相等大小的较大花瓣所掩盖。有证据表明泡花树属的花是一个独特的五部起源，而不是如前所述的三部起源，并支持真双子叶植物中五部起源的多个起源。
Flower developmental studies are a complement to molecular phylogenetics and a tool to understand the evolution of the angiosperm flower. Buds and mature flowers of Meliosma veitchiorum, M. cuneifolia, and M. dilleniifolia (Sabiaceae) were investigated using scanning electron microscopy to clarify flower developmental patterns and morphology, to understand the origin of the perianth merism, and to discuss the two taxonomic positions proposed for Sabiaceae, among rosids or in the basal grade of eudicots. Flowers in Meliosma appear pentamerous with two of the five sepals and petals strongly reduced, three staminodes alternating with two fertile stamens opposite the small petals, and a two-carpellate gynoecium. The flower development in Meliosma is spiral without distinction between bracteoles and sepals. Because of this development, sepals, petals, and stamens are almost opposite and not alternating as expected in cyclical pentamerous flowers. In four-sepal flowers the direction of petal initiation is reversed. The symmetry of the flower appears to be transversally zygomorphic, although this is hidden by the almost equal size of the larger petals. Evidence points to a unique pentamerous origin of flowers in Meliosma, and not to a trimerous origin, as earlier suggested, and adds support to multiple origins of pentamery in the eudicots.