SEED COAT INHIBITS THE PRODUCTION OF ALPHA-GALACTOSIDASE AND ENDO-BETA-MANNANASE IN THE ENDOSPERM OF DEVELOPING CAROB SEEDS

Completion of carob (Ceratonia siliqua L.) seed development required 3 9 weeks after anthesis (W.A.A.). The rate of fresh and dry weight incr ease was very low until 29 W.A.A. At 36 W.A.A., when seed dry weight p eaked, the seeds commenced the maturation drying stage which lasted un til 39 W.A.A. The production of endosperm alpha-galactosidase (EC 3.2. 1.22) started 26 W.A.A. and 3 weeks later the texture of the endosperm started becoming increasingly firm. These two events may be linked be cause of removal of galactose side chains from the mannan backbone. Al pha-galactosidase activity increased further and peaked 37 W.A.A. when no further dry weight deposition was taking place. In contrast to alp ha-galactosidase, endo-beta-mannanase (EC 3.2.1.78) activity was absen t during carob seed development. Carob seeds did not germinate while i n the pod but embryos isolated before the start of the maturation dryi ng were induced to germinate if seeds were subjected to prior desiccat ion. Embryos or seeds germinated, without a requirement for drying if the seeds were removed from the pod during maturation drying. Prematur e desiccation of seeds before maturation drying did not induce the pro duction of endo-beta-mannanase or increase the activity of alpha-galac tosidase. However, there were increases in activities of both enzymes if seeds were kept in a fully hydrated state and endosperms were incub ated without the seed coat, while seed desiccation during the maturati on drying stage, only, caused a further increase in the activities of both hydrolases, but still in the absence of the seed coat. Thus, the seed coat is one control factor in alpha-galactosidase and endo-beta-m annanase production in the endosperm of developing carob seeds.