四种石斛兰种胚发育进程研究

Seed embryo growth courses of four species of Dendrobium orchid

关键词:  石斛兰  胚培养  球形胚  原球体  吸收毛

Key words:  Dendrobium orchid  embryo culture  the globular embryo  protocorm  the absorbing hairs

摘要:

以玫瑰石斛、尖刀唇石斛、短棒石斛、兜唇石斛种子为材料，进行种胚非共生萌发研究，并对其种子形态和胚的发育进程进行了显微观察。结果表明：处于球形胚阶段的石斛兰种子，种胚吸胀后突破种皮，发育至吸收毛和芽生长点出现后，种胚形成原球体；种子萌芽后胚尚未成熟，只进入心形胚阶段。呈纺锤形种子的种皮两端形状不同，一端存在结点，呈弯曲状的尖形，另一端种皮呈收拢的圆口形。4 种石斛兰种子，玫瑰石斛种子最长，为两端狭长的纺锤形；兜唇石斛种子最短，呈两端稍细的纺锤形。玫瑰石斛、短棒石斛、尖刀唇石斛种子胚培养需要5～10 d萌发；兜唇石斛种子和胚皆偏小，萌发需要30 d。石斛兰种胚和种皮吸水膨胀后，种胚向种皮的一端移动、脱出或种胚撕裂种皮中央后突破而出，形成裸胚。玫瑰石斛种子撕裂种皮后主要从种皮中央突破；短棒石斛、尖刀唇石斛、兜唇石斛部分种胚从种皮一端脱出，部分种胚则从中央撑破种皮脱出。充分膨胀、变绿后萌芽的裸胚，存在极性，顶部芽生长点萌动，下部出现成群散射状吸收毛。

Abstract:

Morphological and anatomical microexamination of the embryo development of the seeds of Dendrobium crepidatum，Den. heterocarpum，Den.caillipes and Den.aphyllum were studied. The results showed that the embryo consisted of relatively undifferentiated cells at globular stage. Protocorms were formed after embryo swelling breaking through the seed coat，forming absorbing hairs and initiating shoot apex from the surface. After the seeds germinated，the embryos remained immature and stayed at heart shaped embryo stage. The two ends of the spindly seed were different，one was oblique and subacute，the other was oval. The seed volume and germination time were different in species，and the spindly seed of Den.crepidatum was the longest with sharper points，and the seed mainly broke through the seed coat from the midst of the seed coat. Den.aphyllum seed was the shortest in length with two dullish spindly ends，and the seed germination needed the least 30 d which was much longer than the 5-10 d of other 3 species. In general，after full water absorption，the seed showed swelled，and the embryo seemed to come out from one end or broke through the midst of the seed coat surface，being a naked embryo. The bud growing point sprouted from the upper of the bare embryo，and many absorbing hairs grew out at the base after swelling，turning green and germinating，and protocorm formed at last.