融安黄竹小穗和小花的形态发育

Morphological development of the spikelet and the floret in Dendrocalamus ronganensis (Gramineae: Bambusoideae)

运用扫描电镜对融安黄竹Dendrocalamusronganensis的小穗和小花的发生发育及形态结构进行了研究。其小穗的发育过程是:小穗原基→第一颖片原基→第二颖片原基→第一朵小花的外稃原基→第一朵小花原基→第二朵小花的外稃原基→第二朵小花原基。小穗为由2个颖片和1–2朵小花组成的假小穗。其小花发育的过程是:内稃原基→雄蕊原基→雌蕊原基。内稃在发生上由彼此独立的两个突起形成,随着发育逐渐愈合。观察结果支持内稃是双起源的说法。雄蕊原基近两轮发生。雌蕊原基由小花原基的中央部分直接发育而成。在小花的发育过程中,未观察到鳞被原基的发生。该种的小花是无花被的,结构较为简化,为外稃和内稃包裹的雄蕊和雌蕊组成的结构。与近缘类群做比较,探讨了小穗和小花在竹亚科中的演化。

Morphological development of the spikelet and the floret in Dendrocalamus ronganensis has been studied for the first time under scanning electron microscope （SEM）. The developmental sequence of spikelet is： spikelet primordium→primordium of the first glume→primordium of the second glume→primordium of the first lemma→primordium of the first floret→primordium of the second lemma→primordium of the second floret. The spikelet is a pseudospikelet consisting of two glumes and 1-2 florets. The developmental sequence of floret is： primordium of palea→primordia of stamens→primordium of pistil. The palea originates from two distinct protuberances in its early development, and the two parts gradually unite in late stage of development. The palea has been confirmed to be of a double origin. The primordia of stamens initiate nearly in two whorls. The central part of the floret primordium changes directly into gynoecium. The development of lodicules cannot be observed in the whole process. The floret, consisting of stamens and pistil subtended by lemma and palea, is quite reduced because of the absence of the perianth. The evolution of the spikelet and the floret in the Bambusoideae is discussed based on the comparison of the morphological development of the spikelet and the floret in Dendrocalamus with that in its closely related genera.