ULTRASTRUCTURE OF THE TAPETAL CELL-WALL IN THE STAMENLESS-2 MUTANT OFTOMATO (LYCOPERSICON-ESCULENTUM) - CORRELATION BETWEEN STRUCTURE AND MALE-STERILITY

In the stamenless-2 (sl-2) mutant of tomato (Lycopersicon esculentum M ill.), the breakdown in microsporogenesis corresponded with various ab normalities in the ultrastructure of the tapetal cell wall. In some mu tant anthers, the inner tangential wall was excessively loosened allow ing the passage of tapetal cell wail material and cytoplasmic contents into the anther locule. This presumably altered the osmoticum of the locule and resulted in plasmolysis of the microspores. Membranous frag ments commonly observed in the normal tapetal cell wall, and presumed to have a role in transfer of materials from the tapetum to microspore s, were absent from the sl-2 mutant. This was associated with reduced transfer of materials, such as lipids, to the developing pollen grains . In addition, a lining of sporopollenin-like deposits that coated the inner tangential wall of the normal tapetum, was discontinuous in the mutant. In mutant anthers where the tapetal cell wall did not loosen, the transfer of all materials was restricted and this resulted in the collapse of sporogenous material.