Induction of hormone sensitivity by dehydration is one positive role for drying in cereal seed

Abstract

THE hydrolysis of food reserves in seeds (usually fats, starch and protein) is closely linked to embryo growth since it does not begin until germination has started. The control of food mobilisation by the embryo is best understood in cereals such as barley and wheat. In these cases the hormone gibberellin, moving from the embryo, activates the aleurone layer to produce an array of hydrolytic enzymes, including α-amylase, protease and β-1,3-glucanase and to secrete them into the endosperm where stored materials are located1. The stored food is of course laid down in the grain during its development on the mother plant. But at the time when this accumulation is taking place the grains contain relatively high levels of gibberellin2; nevertheless, the food reserves seem free from hydrolytic attack. One possible reason for this is that in undried grains on the mother plant the hormonal control system for enzyme synthesis and secretion does not function. No research has been done directly on this problem; what relevant research there is shows some discrepancies3,4. Our results, described here, demonstrate that the hormonal control system operates fully only after the mature grains have been dried. Dehydration is necessary for the development of complete sensitivity to gibberellin.