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

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.