根瘤形成过程中刺槐根外层传递细胞的诱发和超微结构观察

Inducement of transfer cells and ultrastructural observation of root parts during the formation of Robinia pseudoacacia's root nodule

通过对接种根瘤菌后的刺槐根段进行透射电镜观察 ,结果表明 :加菌刺槐苗中发生形态变化的根段在不同时期 (根毛密集形变、根段膨大、初期小瘤一直到成瘤 )根外层细胞的外切向壁上可形成具壁内突的传递细胞。而未加根瘤菌的刺槐苗根段的外层细胞以及加菌但没有形态变化的刺槐苗根段均未观察到传递细胞。大量实验观察表明刺槐根外层传递细胞的产生是根瘤菌诱导所致。传递细胞不仅发生于刺槐根表皮细胞中 ,也可产生于外皮层细胞中 ,甚至于根毛细胞中。所取加菌刺槐苗形变根段的根外层细胞有些全部由传递细胞组成 ,有些为传递细胞与非传递细胞相间排列。传递细胞的发育最先是质膜向内突起形成囊状结构 ,然后细胞壁物质开始沉积 。

The ultrastructure of the roots of Robinia pseudoacacia was studied by TEM. The result showed that in the different deformed root epidermal or exodermal cells of Robinia pseudoacacia there were transfer cells with wall ingrowths well developed on the extangential wall. There was no wall ingrowths in root epidermal cells of Robinia pseudoacacia which was not inoculated with rhizobia and the one inoculated with rhizobia but no swollen root parts. Comparison of the roots of inoculation and non inoculation suggested that transfer cells were induced by rhizobia. Transfer cells laid not only in epidermal cells but also in the outer 1～2 layers of exodermis even in root hair cells. The arrangement of transfer cells during different periods was different, continuous or interval. Membrane ingrowth was first observed at the initial stage of the formation of transfer cells, then the wall material gradually deposited, at last transfer cells were formed and lasted until the formation of the root nodule.