Soaking injury and its reversal with polyethylene glycol in relation to respiratory metabolism in high and low vigor soybean seeds

Abstract

Germination and growth of unaged (high vigor) and accelerated aged (41°C and 100% RH for 4 days; low vigor) soybean [Glycine max (L.) Merr. cv. Essex] seeds were severely reduced by soaking the seeds under water at 25°C during the first 1 to 8 h of imbibition. Soaking in 30% polyethylene glycol (PEG) did not injure high vigor seeds and improved the performance of low vigor seeds. Soaking in water increased subsequent RQ values and acetaldehyde and ethanol levels. In high vigor seeds, the increase in RQ lasted only 1 h after transfer to aerobic conditions, whereas in low vigor seeds the increase persisted into the second h. Increases in ethanol and acetaldehyde after soaking were more pronounced in low than in high vigor seeds. The data indicate that relatively short periods under water can cause water uptake injury to imbibing soybean seeds and that this injury can be avoided by osmotically reducing the initial rate of water uptake. Seeds whose vigor has declined during accelerated aging show an additional injury which increases with soaking duration and involves alterations in respiratory metabolism including accumulation of acetaldehyde and ethanol to high, and possibly toxic, levels during imbibition.