THE EFFECT OF EXTERNAL PH ON THE GIBBERELLIC-ACID RESPONSE OF BARLEY ALEURONE

During development and germination of cereal grains, the pH of the end osperm decreases to values of 4 to 5. To increase the insight into the physiological function of low endosperm pH, we studied the effect of external pH on the gibberellin (GA) response of the aleurone layer, wh ich surrounds the endosperm. Analysis of the GA3 dose-response curve o f the secretory enzyme alpha-amylase (EC 3.2.1.1) and of the glyoxysom al enzyme isocitrate lyase (EC 4.1.3.1) demonstrated that a reduction in medium pH from 6.0 to 3.7 enhanced the GA3-response of isolated bar ley (Hordeum vulgare L.) aleurone layers. Since the aleurone itself ap pears to be involved in the reduction of the endosperm pH, the tissue might consequently influence its own hormone response.