柿树炭疽菌侵染柿树叶柄的超微结构观察

(Ultrastructure of infection of persimmon petiole by Collectotrichum gloeosporioides)

利用透射电镜技术研究了柿树炭疽菌侵染柿树叶柄的超微结构。结果表明:病原菌侵入寄主细胞后,产生细胞内的初生菌丝,其表面沉积凹凸不平的电子不透明物质。一层界面基质(interfac ialm atrix)把表初生菌丝细胞壁和凹陷的寄主原生质膜分开。随着初生菌丝定殖下一个细胞,原先细胞中的细胞膜消失,形成许多泡囊,随后叶绿体消失,内质网和高尔基体也逐渐降解,最后细胞内物质全部被降解成电子不透明的颗粒,降解的物质沿着初生菌丝和细胞壁表面沉积。初生菌丝穿透细胞壁的过程中,菌丝顶端接触细胞壁后膨大,并在中部产生一个隔膜,然后顶端细胞产生一个较细的穿透菌丝,穿透寄主细胞壁。穿透菌丝在寄主细胞壁中的狭窄处产生一个隔膜,一旦穿透寄主细胞壁后,迅速膨大。次生菌丝在细胞间和细胞内扩展,通过菌丝体对细胞壁施加的机械压力引起寄主细胞壁破裂,或同初生菌丝一起使细胞壁解体。侵染90 h后,形成垫形分生孢子盘。在分生孢子盘周围的表皮细胞中,次生菌丝不断形成子座组织,使原来的子座扩大,子座不断分化形成产梗细胞,产梗细胞产生分生孢子梗,分生孢子梗生长和发育对角质层和表皮细胞壁组织折叠处施加机械压力,使角质层和表皮细胞壁组织进一步折叠,分生孢子盘也相应扩大。

The ultmstructure of persimmon petiole infection by C. gloeosporioides was examined by transmission electron microscope. It was found that the intracellular primary hypha of the pathogen was developed and deposited by a layer of accidented electron-opaque material after invading host tissue. An interfacial matrix separated the cell walls of primary hyphae from the invaginated plasma membrane. After primary hyphae started to colonize adjacent ceils, the ceils infected previously began to degenerate. First, the plasma membrane disappeared and formed a lot of uneven vesicles; then, chloroplast vanished, endoplasmic reticulum and golgi apparatus began to disrupt; finally, host cells were disorganized completely into electron-opaque particles, depositing along the cell wall of primary hyphae and inner cell wall of host. In the process of penetration, the top cell of primary hyphae became swollen when contacting host cell wall and produced a septum in its middle, then formed a narrow penetration hyphae, penetrating the host cell wall. The penetration hyphae produced a septum at the extreme constriction and again became rapidly intumescent once it went through cell wall. Secondary hypha extended both intercellularly and intracellularly, causing the host cell wall to break down by mechanical pressure it exerted to host cell wall, or together with primary hyphae making the host cell wall to disorganize, and forming pulvinate acervuli by 90 h. In epidermis near a acervulus, the dense secondary hypha formed hyphal stroma continuously, and these caused previous hyphal stroma to enlarge. As a result, the conidiophorogenous cells developed from the hyphal stroma one by one, then conidiophores gave rise to them successively. The developing conidiophores exerted the mechanical pressure to the fold point of epidermal cell and cuticle tissue to make it to fold further, resulting in acervulus to expand.