青枯菌侵染桉树幼根的组织病理学研究

接种青枯菌后不同时间切取桉树幼根根表、根横切面和纵切面进行制样，扫描电镜观察其组织病理学变化。结果显示：接种0．5h后即有少量病菌存在于根表细胞间隙和导管间隙，但寄主表皮细胞和维管束结构基本完好；接种2h，表皮细胞壁被破坏，细胞瓦解；接种24h，表皮细胞间出现较大裂隙．在横切面和纵切面上可观察到大量细菌聚集并结为白色絮状物．导管破裂并被堵塞；此时植株外观上也开始出现萎蔫症状。

Histopathological study on young roots of eucalyptus invaded by Ralstonia solanacearum

The epidermis,cross and vertical sections of young roots of a eucalyptus clone inoculated with Ralstonia solanacearum for various time were excised and prepared for scanning electron microscopy(SEM)observation.Only a few bacteria were present in the intercellular spaces of epidermal tissue and the spaces between vessels 0.5 h after the inoculation,the epidermal ceils and vascular tissue,however,were virtually unaffected.The cell walls of epidermis were broken and the cells were disintegrated 2 h after the inoculation.Big cracks appeared on the epidermis,massive bacteria aggregated in white flocs,the vessels were blocked and disrupted 24 h after the inoculation when while the wilt symptom began to show on the eucalyptus ramet.