Aspects infrastructuraux des altérations des anthères de Silene dioica parasitées par Ustilago violacea

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Abstract
The structural characteristics of the sporogenous and parietal tissues of healthy anthers of S. dioica (L.) Clairv. (Caryophyllaceae) are described as well as those of anthers infected by U. violacea (Pers.) Rouss. (Ustilaginales). In infected anthers, the invading dikaryotic mycelium grew intercellularly and very rarely penetrated the cells. The pathogen stopped stamen histogenesis at an early stage, causing necrosis specifically of the sporogenous tissue either directly or following hypertrophy. Five stages were distinguished during the histological modifications leading to anther destruction. First, the mycelium developed in the anther filament and spread throughout the superficial tissues of the anther without causing histological changes in the anther. Then, some sporogenous cells began to show necrosis and formed compact masses. An increasing number of sporogenous cells became necrotic following strong vacuolization and hypertrophy. Hyphae grew profusely in the necrotic mass of sporogenic cells. Finally, the fungus produced teliospores which filled the sporangial cavity.