大白菜软腐细菌从幼根侵染的组织病理学研究

 将大白菜种子置于培养皿内的滤纸上发芽。滤纸用不同浓度的洗涤与不洗涤的软腐欧氏杆菌(Erwinia carotovora pv.carotovoar Dye)悬浮液,离心上清液,培养基浸出液和灭菌生理盐水浸润。在25℃下培养26小时后,用细菌悬浮液处理的幼芽发病率为8-95%不等。病苗生长量为对照(用生理盐水处理)的17-80%。扫描电镜观察的结果指出,接种后病原细菌首先在根毛区发现,以后才在伸长区和成熟区发现大量病菌。成熟区表皮细胞与细胞交界处的细胞壁有被分解的迹象。在幼苗的导管及其附近的薄壁细胞内均发现了病原细菌,检出率分别为16%和3%。在病苗组织内和幼根表面的病菌可产生微纤丝。病苗幼茎经压气处理24小时后,对其断面进行扫描电镜观察,结果表明,病菌可将导管的外壁与纹孔膜分解而使导管解体仅剩螺蚊加厚部分或呈网孔状。

INVESTIGATION ON HISTOPATHOLOGY OF YOUNG ROOT OF CHINESE CABBAGE INFECTED WITH Erwinia carolovora PV.carolovora DYE

Chinese cabbage seeds germinated on wetted filter paper in the petri dishes.The solution to wet the filter paper included washed and unwashed bacterial suspension,the supernatant,the extract of the medium and physiological saline (0.8%) as a control.After incubation at 25℃ for 26 hrs,the diseased plants reached 8-95% of the total seed-lings treated with various suspensions containing the soft rot bacteria.The height of the diseased seedlings ranged from 17% to 80% of the control.The observations on the surfaces of the diseased young roots by the scanning electron microscpe indicated that a great number of the bacteria attached preferentially to the root-hair region earlier and to the growing and mature regions of the root later.It was evident that the cell walls of the mature regions were degraded by the bacteria and the holes were eventually formed by the perferation of the pathogen on the adjacency of the epidermal cells.The bacteria were found in the vessels and parachyma cells of the diseased seedlings at 16% and 3% of the examed sections respectively.The bacteria in the tissues of the infected seedlings could produce the microfibrils.The pathogenic bacteria in the vessels could destroy the vessel walls to make the vessel elments loose (spiral vessels) and multiporous (pitted vessels).