荷花“重瓣化”的花器官形态发育比较观察

荷花（Nelumbo nucifera）的花型可分5种，最原始为单瓣型，然后由单瓣演化出半重瓣、重瓣、重台和千瓣型。为了揭示荷花重瓣化的分子机理，有必要从花器官的形态发育特征探究荷花花型成因及“重瓣化”的形态发育特征。实验分别选取5种荷花花型的代表品种：‘单洒锦’（单瓣型）、‘大洒锦’（重瓣型）、‘中山红台’（重台型）、‘至尊千瓣’（全重瓣型）、‘千瓣莲’（千瓣型）为材料，进行花芽分化过程形态的石蜡切片比较观察。结果发现：花芽分化过程中5个品种的萼片原基分化期和花瓣原基分化期相似，而雄蕊和雌蕊原基发育存在明显差异：单瓣、重瓣和重台品种均有正常的雄蕊和雌蕊原基分化；全重瓣品种发育初期有雄蕊及雌蕊原基分化，但后期全部瓣化；‘千瓣莲’品种不形成雄蕊和雌蕊原基，而是直接形成2至多个“花瓣增殖中心”，并由此不断分化出细小花瓣。研究认为重瓣型荷花品种的“重瓣化”花瓣主要来源于雄蕊的向心式瓣化，其次是雌蕊瓣化，属于雌雄蕊起源。而对于‘千瓣莲’型品种，花瓣的具体来源方式、花托是否直接参与瓣化及其在重瓣化过程中的作用有待于结合分子生物学手段开展进一步研究。

Comparison of Floral Organ Morphological Development between Single and Double Flowers in Nelumbo nucifera

Five forms of flower are included in lotus （ Nelumbo nucifera）. The single flower is the primitive type of lotus flowers, followed by semi-double, double, duplicated and thousand-petalled flower. To understand the molecular mechanism underlying the flower doubling in Nelumbo, it is necessary to investigate morphologically the origin of different flower forms. We studied the differentiation of lotus floral buds by paraffin section of five cultivars in N. nucifera, representing the five forms of flower, i.e.‘ Dan Sajin＇ （single） ,‘ Da Sajin＇ （double） , ‘Zhongshan Hongtai＇ （duplicated）,‘Zhizun Qianban＇ （fully-double） and ‘Qianban Lian＇ （thousand-petafled）, respectively. The anatomical examination showed that the differentiation of the sepal and petal primodia shared a similar pattern, but the stamen and carpel primordia were distinct in differentiation. The normal differentiation processes of stamen and carpel primordia were observed in the flower buds of single, double and duplicated-petalled cultivars. However, in ‘ Zhizun Qianban＇ , a fully-double euhivar, all the primordial stamens and carpels were transformed into the petals. The thousand-petalled cuhivar didn＇ t produce either stamen primordia or carpel primordia but developed the tiny petals instead. These results suggested that the petals of double-flowered lotus were mainly derived from the petalodyof stamens, followed by pistils. For the thousand-petalled cuhivar, further molecular studies are needed to understand the origin of the petals and the role of receptacle in flower doubling of lotus.