Differential leakage of substances from two soybean genotypes during imbibition is influenced by seed coat pore characteristics

Soybean (Glycine max [L.] Merrill) seed coat and embryo damage is the major cause of excessive electrolyte leakage during imbibition. No studies have examined the influence of seed coat pore morphology on differential leakage between soybean genotypes. The objective of this study was to characterize substances leaking from two soybean genotypes [Ohio Food Grade 1 (OFG1) an d an experimental line, 9544544] which differ in seed coat pore characteris tics. Mature (10 to 11% water content, fresh mass) field produced seeds wer e observed for seed coat damage and pore characteristics under light and sc anning electron microscopes following 7 to 10 d storage in a cold room (4 d egrees C, 47% RH). Leachates from seeds in Petri dishes lined with moistene d germination blotting paper were examined at 2 h intervals until 30 h imbi bition for substances including metabolites, UV absorbing substances and ma late dehydrogenase activity. An increase in leakage of all substances with time was observed until radicle protrusion. The pattern of leakage was the same in both genotypes, but OFG1 consistently showed higher leakage than 95 44544. Although a general decline in leakage of all substances occurred aft er radicle protrusion, suggesting an increased metabolite mobilization duri ng seedling growth, the pattern of leakage was not linear. In conclusion, t his study demonstrates that during soybean seed imbibition 1) most compound s examined leaked more followed by a reduction in leakage after radicle pro trusion, 2) a differential leakage in soluble carbohydrates was observed wh ere free cyclitols > reducing sugars > oligosaccharides > galactosyl cyclit ols and 3) these leakage characteristics may be attributed to genotype and seed coat pore characteristics. It is also suggested that osmolality could be a useful measure of seed leaching.