茭白分蘗苗端的结构及发育研究

Structural and Developmental Studies on the Titter Apex of Zizania Caduciflora Hand-Mazz

茭白生育过程可分为四个时期:萌发期、分蘖期、苗端增粗期、休眠期。生长锥在各阶段始终保持原套—原体结构,原套两层细胞。叶原基发生的最初标志是原套细胞在叶原基发生位点上的平周分裂。最初的腋芽原基发生在苗端倒数第3间隔期所形成的幼叶叶腋内,发生的早期出现壳状区结构,促仗腋芽原基外突。不定根发生的最早阶段约在苗端倒数第5节间的上部,起源于幼茎外围堆管束的外侧一层薄壁细胞。茭瓜是茎的变态,它的侧生腋芽退化,没有膨大。茭瓜的膨大可归因于:基本组织的细胞分裂、细胞体积增大和胞间隙扩大等。茭白苗端的淀粉分布及消长规律与苗端的分区结构和器官发生都有密切相关性。

The present paper deals with a preliminary study on the structure and development of the tiller apex of Zizania caduciflora Hand-Mazz.The results of observation are summarised as follows:Development of Z.caduciflora is divided into four periods in this paper, namely: germination period,tillering period,hypertrophy period and period of dormency.During the development of all these periods, tunica-corpus structure of the shoot meristem can always be distinguished.Tunica of Z.caduciflora is double layered.The first sign of leaf primordium development is the periclinal divisions of the tunica cells at the site of initiation.The earliest lateral bud primordium arises in axil of the second leaf from the apex,and a shell zone is appeared in associating with an active outward pushing of the bud primordium at the early stage of its initiation.The uppermost adventitious roots initiate from a layer of parenchyma cells next to the outer vascular bundle which is about in the upper part of the fifith internode from the shoot apex.The hypertrophied shoot is a kind of deformed stem of the host plant with its lateral buds ceased in their development. Hypertrophy of the shoot is performed by the following causes;those are: division of parenchyma cells of the ground tissue,expansion of the dividing ceils and enlargement of intercellular spaces.It is found that the regularity of distribution, growth and diminishing of starch grains are closely related to the structure and organogenesis of the shoot apex.