尼泊尔马桑放线菌共生固氮根瘤的感染和发育

弗兰克氏放线菌通过感染尼泊尔马桑的根毛侵入根的皮层细胞。由于内生菌侵入的刺激,部分皮层细胞分裂和增大,产生前根瘤原基。根瘤原基分裂、分化,形成初生根瘤瘤片。瘤片顶端分生组织不断双叉分枝,发育,并伴随着内生菌感染的寄主细胞,产生多次双叉分枝的珊瑚状根瘤。观察瘤片的横切面,含菌组织是一个马蹄形的致密整体,不完全地包围着稍偏的中柱。观察瘤片的纵切面,可将其划分为6个区域,即顶端分生组织,未感染皮层细胞组织、新感染含菌组织、成熟含菌组织、衰老含菌组织和中柱及其外围数层富含淀粉粒的皮层细胞。

INFECTION AND DEVELOPMENT OF SYMBIOTIC NITROGENFIXING ACTINORHIZA OF CORIARIA NEPALENSIS WALL.

Frankia hyphae penetrate root ha rs and invade root cortical cells of Coriaria nepalensis Wall., leading to nodulation. Owing to the stimulation caused by infection, a part of the cortical cells in the infected root divide and hypertrophy, resulting in the formation of a prenodulein which the nodule primordium develops. The primordium divides and differentiates, forming a primary nodule lobe. The apical meristem of a lobe hranchs dichotomously and the branchings develop with the infection of new host cells by the endophytes, giving rise to a coralloid root nodule consisting of many dichotomic branchings. In cross section, the endophyte-infected tissue zone in a lobe is a horse-shoeshaped compactmass, incompletely surrounding the acentral stele. In longitudinal section, the apical part of a mature lobe is the meristem, followed successively by the non-infected tissue, the newly infected tissue, the mature infected tissue and the senescent infected tissue. The lobal stele is surrounded by several layers of cortical cells containing starch granules.