Acidification, growth promoter and red light effects on germination of skotodormant seeds of Hygrophila auriculata

Abstract

A period of dark storage (DS) induced skotodormancy in seeds of Hygrophila auriculata. Seeds without previous DS germinated 22%. A single 10-min red light (R; 1.5 μmol m −2s −1) treatment induced about 70% germination. Five daily 10-min R treatments increased germination further to about 80%. Gibberellin A 3 (GA 3) at 10 −6 M or higher promoted germination while R + GA 3 at 10 −4M or higher induced 85% germination or higher. After a period of 5–30 days of DS, germination responses induced by terminal R or GA 3 were reduced, indicating an increase in the degree of skotodormancy. GA 3 alone at 10 −3 M induced about 60–80% germination in these DS seeds. In 10-day DS seeds any combinations of ethylene, benzyladenine, or thiourea given with R resulted in >80% germination. Acid immersion (in HCl solution at pH 1.1 for 30 min) alone had no effect on germination of these DS seeds. However, these skotodormant seeds germinated >-80% if acid immersion was followed by terminal treatments of either five 10-min R, or 10 min R + GA 3 at 10 −4M or higher. The results in this study deviated from the 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 apply in the same way to skotodormant Hygrophila seeds.