Germination of papaya seed in response to desiccation, exposure to subzerotemperatures, and gibberellic acid

The effects on germination of two lots of Carica papaya seed of dehydration at 25 degrees C, followed by exposure to -20 degrees C or -196 degrees C, were evaluated with and without gibberellic acid (GA(3)) treatment. In the absence of GA(3) treatment, dehydration increased subsequent germination on ly in seed lot 1 when moisture content (m.c.) was reduced from 59% to 6.0% and 5.3%. In seed lot 2, dehydration followed by exposure to -196 degrees C increased germination compared with dehydration alone. Treatment with GA(3 ) enhanced germination rate in all treatments. Dehydration to 5.3% (lot 1) or 6.9% and 6.8% m.c. (lot 2), followed by exposure to subzero temperatures and treatment with GA(3), were the most favorable combined treatments to e nhance papaya seed germination. The results suggest that papaya seed presen ts an orthodox behavior, permitting germplasm conservation in conventional and cryogenic genebanks.