Abnormal anther development and high sporopollenin synthesis in benzotriazole treated male sterile Helianthus annuus L.

Foliar application of 1.5% benzotriazole induced 100% pollen sterility in H. annuus. Pollen abortion in treated plants was mainly associated with abnormal behaviour of tapetum. A limited number of anther locule showed early degeneration of tapetum followed by disintegration of sporogenous tissues. On the other hand, some locules showed normal development of tapetum at initial stages. However, this tapetum exhibited degenerated and non-functional cell organelles. In both these situations tapetum failed to provide proper nourishment to developing microspores. The ultrastructure of both tapetum and microspores is different from that of control material with irregularities of exine deposition, endopolyploidy of tapetal nuclei and an alteration of organelle composition being correlated with sterility. Pollen grains thus developed were devoid of nucleus and cell organelles and were complete sterile.