ACIDIFICATION, GROWTH PROMOTER AND RED-LIGHT EFFECTS ON GERMINATION OF SKOTODORMANT SEEDS OF HYGROPHILA-AURICULATA

A period of dark storage (DS) induced skotodormancy in seeds of Hygrop hila auriculata. Seeds without previous DS germinated 22%. A single 10 -min red light (R; 1.5 mumol m-2 s-1) treatment induced about 70% germ ination. Five daily 10-min R treatments increased germination further to about 80%. Gibberellin A, (GA3) at 10(-6) M or higher promoted germ ination while R + GA, at 10(-4) M or higher induced 85% germination or higher. After a period of 5-30 days ofDS, germination responses induc ed by terminal R or GA3 were reduced, indicating an increase in the de gree of skotodormancy. GA, alone at 10(-3) M induced about 60-80% germ ination in these DS seeds. In 10-day DS seeds any combinations of ethy lene, benzyladenine, or thiourea given with R resulted in > 80% germin ation. Acid immersion (in HCI solution at pH 1.1 for 30 min) alone had no effect on germination of these DS seeds. However, these skotodorma nt seeds germinated greater-than-or-equal-to 80% if acid immersion was followed by terminal treatments of either five 10-min R, or 10 min R + GA3 at 10(-4) M or higher. The results in this study deviated from t he lettuce model [HSIAO and VIDAVER (1989) J. exp. Bot. 40, 23-31] in that skotodormant Hygrophila seeds could be induced to germinate by a high GA concentration without acid pre-treatment. The conversion of X --> X' and Y --> Y' postulated in the lettuce model does not seem to a pply in the same way to skotodormant Hygrophila seeds.