降香黄檀着叶期和无叶期次生韧皮部筛分子的超微结构

ULTRASTRUCTURE OF SIEVE ELEMENTS IN SECONDARY PHLOEM OF DALBEGIA ODORIFERA DURING LEAFBEARING AND LEAF-ABSENT PERIOD

利用透射电镜技术研究了生长在海南岛的热带落叶树降香黄檀(Dalbegia odorifera T.Chen)1—2年生枝条着叶期和无叶期次生韧皮部筛分子的超微结构,并就这两个时期的筛分子进行了比较。着叶期每个成熟筛分子内有一个带尾的纺锤形P-蛋白质体,主体由稠密而散乱的P-蛋白质细纤维组成,尾部呈结晶状;筛分子具有横向端壁和单筛板,在邻近筛板处,细胞壁向筛分子腔内形成明显的突起。无叶期仍然保持着与着叶期大致相同厚度的有功能韧皮部,筛分子具有正常的原生质体,P-蛋白质和筛板孔的结构也与着叶期的相同,但筛分子内有较多的淀粉粒和囊泡。

Ultrastructures of sieve elements of secondary phloem of 1—2 year old branchlet of tropi- cal deciduous tree Dalbegia odorifera T.Chen growing on Hainan Island were studied under transmission electron microscope and a comparation was made between the sieve elements in leaf-bearing and leaf-absent period.During the leaf-bearing period,there was a tailed spindle- shaped P-protein body in each mature sieve element.The main part of the P-protein body con sisted of a disordered fine fiber mass with two (?)ystalline tails.The sieve elements had hori- zontal end walls with simple sieve plate.The inner layers of the wall near the sieve plate ap- peared intumescent, protruding into the sieve element lumen.During the leaf-absent period,a functional phloem remained about the same thickness as that during the leaf-bearing period. The sieve elements in the leaf-absent period contained normal protoplasts and the P-protein and the sieve plate pores had the same structures as those during the leaf-bearing period.More starch grains and vesicles were found in sieve elements in the leaf-absent period.