缺镁与正常供镁的菜豆组织结构比较研究

 通过光学显微镜和电子显微镜的观察，研究了缺镁对菜豆植株组织结构的影响。结果表明：缺镁培养的菜豆植株叶片细胞中叶绿体数量增多，并有淀粉粒积累。外部表现出严重缺镁症状后，叶片细胞失去原有的正常形态，细胞收缩，细胞间隙增大，最后细胞破裂，内溶物丧失，栅栏组织和海绵组织结构均消失，叶片厚度减少。叶柄和茎的粗度在缺镁时较小，叶柄中维管束发育不良，数目少。叶脉中维管束占的比例小。叶脉韧皮部细胞膜上ATPase活性在缺镁时较低，电镜下观察到细胞膜上黑色的铅沉淀少；正常供镁的主脉韧皮部细胞间胞间连丝较多。

The Comparative Study on Anatomical Structure of Common Bean Plant With Mg Deficiency and Normal Mg Supply

The paraffin cut section of bean (Phaseolus vulgaris L.) plant materials was observed on the changes of the anatomical structure due to Mg deficiency using light microscope. The results indicated that Mg deficiency caused leaf mesophyllic cells shrunk,deformed, and the increased space among cells. Those severe symptoms of Mg deficiency in leaf were collapse of cells, destruction of palisade tissue and spongy tissue, and decrease of leaf thickness. The diameters of stems and leaf petiole of bean plants with Mg deficiency were smaller than that of those plants with normal Mg supply. The number of vascular bundle in petiole of primary leaves and first trifoliate leaves were 7 and 9,respectively, whereas those values were 13 and 12 respectively at the same site in plants with normal Mg supply, indicating that Mg deficiency might result in poor development of vascular bundle. Investigation carried out with electron microscope indicated that an accumulation of starch grains in chloroplasts was found due to Mg deficiency. ATPase location in plasma membrane of phloem cells in lateral veins and major veins was based on Pb precipitate observed with electron microscope. Mg deficiency seemed to inhibit ATPase activity in phloem cells. Plasmodesmata linking cells in phloem just found in major veins with normal Mg supply. Under Mg deficiency, poorly developed vascular bundle in stems, petioles, and veins and lower ATPase activity in phloem cells could be an explanation for the accumulation of starch grains in chloroplasts.