Evolutionary study of one-leaf plants (Gesneriaceae)

单性在单藓属和苦苣苔科Streptocarpus中均有表现。它们的植物体由一个大子叶组成。它们在整个生活史中从不形成茎或叶片，它们在子叶片的基部产生花序。本研究旨在从分子系统发育分析和比较形态发生的角度来阐明单纲植物的进化。研究材料不仅包括各子叶植物，还包括同子叶植物。它们分别在婆罗洲、马来半岛（包括泰国）、马达加斯加、南非和巴西进行了三次植物考察。各向异性子叶植物的胚保持在鱼雷期，种子萌发期间和种子萌发后分别由下胚轴尖端和两个子叶之间形成根尖和茎尖。茎尖生长太慢，不能形成营养茎，在单叶植物中，一个叫做沟槽分生组织的初级分生组织直接成为生殖茎尖。沟槽分生组织被认为是与茎尖同源的，而不是一个新生的分生组织。增加子叶是由位于子叶基部的基生分生组织的长期活动而产生的。基生分生组织的演化过程及其机制尚不清楚。然而，对Streptocarpus和Chirita茎生种的形态分析表明，它们的大子叶和叶片的发育模式具有相似性；两叶的生长主要依靠基部的分生组织细胞。它们的叶片没有其他双子叶叶片典型的明显的板分生组织。在各向异性子叶植物中，板块分生组织受到的抑制可能比叶片更强烈，导致了基生分生组织的建立。综上所述，单叶植物可能是通过胚胎发育迟缓和随后的营养芽生长抑制而进化的。少

Monophylly is exhibited in Monophyyllaea and in Streptocarpus (Gesneriaceae). Their plant body consists of a single large cotyledon. They never form stems or foliage leaves throughout their life history, and they produce inflorescences at the base of the cotyledon lamina. This research aims to clarify the evolution of the monophylly based on the molecular phylogenetic analysis and comparative morphogenesis. Research materials include not only anisocotylous Gesnerioideae but also isocotylous Cyrtandroideae. They were collected in Borneo, Malay Peninsula including Thai, Madagascar, South Africa, and Brazil on three botanical expeditions. The embryo of anisocotylous Gesnerioideae remains at the torpedo stage, and during or after seed germination the root apex and then shoot apex are formed from the hypocotyl tip and between the two cotyledons respectively. The shoot apex grows too slow to form the vegetative shoot, and in monophyllous plants a rudimentary meristem called groove meristem b … More ecomes directly the reproductive shoot apex. The groove meristem is considered to be homologous to the shoot apex, not a de novo meristem. The accrescent cotyledon is produced by the prolonged activity of the basal meristem located on the cotyledon base. The evolutionary course of the basal meristem and the underlying mechanism still remains to be solved. However, morphological analysis of caulescent species of Streptocarpus and Chirita shows that there is a similarity in the developmental mode between their large cotyledon and the foliage leaves ; the both leaves grow mainly due to the meristematic cells in the basal portion. Their foliage leaves do not have an apparent plate meristem typical of other dicotyledon-leaves. It seems likely that the suppression of the plate meristem occurred more strongly in their cotyledon than the foliage leaves, resulting in the establishment of the basal meristem in anisocotylous Gesnerioideae. In conclusion, one-leaf plants may have evolved through retardation of the embryogenesis and consequent suppression of the vegetative shoot growth. Less