甜菊不同层次叶片叶绿体超微结构观察及其糖苷含量变化

甜菊Stevia rebaudiana Bertoni不同层次叶片叶绿体超微结构的观察及其糖苷含量的测定表明:在上层幼嫩叶片中,叶绿体小,类囊体膜较简单,基粒片层和基质片层数量少,糖苷含量居中。在中层成叶的叶片中,叶绿体大,类囊体膜复杂,基粒片层多,基质片层密集,在基质中出现“淀粉区”结构,糖苷含量最高。在下层衰老的叶片中,叶绿体趋于解体,类囊体膜退化,糖苷含量最低。上述结构与功能密切相关,说明甜菊在现蕾期,中层叶最多,且糖苷含量也最高,是收获的最适时期。

THE ULTRASTRUCTURE OF CHLOROPLASTS IN Stevia rebaudiana Bertoni LEAVES AT DIFFERENT LAYERS AND CHANGES OF STEVIOSIDE CONTENT

The ultrastructure of chloroplasts in Stevia rebaudina Bertoni leave was observed using electron microscope and the changes of stevioside content was determined.The results showed that the chloroplasts of the young leaves at upper layer were small and thylakoid membrane was simple.There were few grana lamella and stroma lamella.The stevioside content was moderate. The chloroplasts of mature leaves at middl?layer wer large. The thylakoid membrane was complex and grana lamella was in large number. The stroma lamella was dense and "starch zone" appeared in the stroma. The stevioside content was the highest.The chloroplast in the senescent leaves at lower layer tended to disintegrate.The thylakiod membrane was degenerate and the stevioside content was the lowest. The data showed that the flower bud stage of Stevia rebaudiana is the most suitable time for harvest.