豌豆根瘤胞间细菌的扩展及其“前途”

SPREAD AND "FUTURE" OF INTERCELLULAR BACTERIA IN PEA ROOT NODULES

中国张家川豌豆根瘤是一种很特殊的根瘤,它的侵入线体积较大,数量很多,在所有发育阶段的寄主细胞中几乎都存在。此外,它还有许多基质丰富,含细菌很少,通常没有壁的类侵入线结构,有时它们的膜、壁和基质还分别与附近侵入线的膜、壁和基质连在一起。在这种根瘤中,胞间细菌不仅能以侵入线方式向新形成的分生细胞扩展,而且也能通过胞间层和胞间隙向根瘤端部白色区域移动。虽然多数侵入线能向寄主细胞释放细菌,但有的直到寄主细胞衰败也无细菌释放,即使细菌在侵入线壁解体后有机会进入这些衰败细胞,它们也很快被细胞中的酶所消化。

Chinese pea (Pisum sativum cv Zhang Jiachuan) root nodule is a kind of quite special root nodule in which infection threads are larger in size and also a good many in number, they almost appear in all developmental stages of the host cells. At the same time, in the root nodules there still are a large quantity of infection-thread-like structures in which matrix is specially abundant, however, bacteria are less in number. The wall thickness of the infection-thread-like structures is very thin. The structures are often near infection threads, sometimes their membranes, walls and matrix connect with the membranes, walls and matrix of nearby infection threads. The spread of intercellular bacteria in the root nodules mainly depend on the continuous growth of infection threads towards new forming meristematic cells, they can also move to the end white regions of the root nodules through the middle lamella and the intercellular spaces. Though the majority of infection threads in the root nodules can release their bacteria into the host cells, the minority of infection threads do not release their bacteria into the host cells till the host cell senescing or disintegrating. Even if some bacteria are released into the host cells from the holes formed by disintegration in the infection thread walls, they are rapidly digested by some enzymes in the host cells.