Physiological, Biochemical, and Ultrastructural Changes in Naturally Aged Sweet Corn Seeds

Abstract

Due to low starch content and poor seed vigor, sweet corn seeds exhibit poor storage stability. Therefore, understanding the physiological and biochemical changes in seeds after natural aging is crucial for assessing seed status and extending the storage period. This study aims to investigate the physiological, biochemical, and ultrastructural changes in aged seeds of different genotypes. An eight-month natural aging experiment was conducted on 10 sweet corn inbred lines. The results showed an obvious decrease in germination potential, germination ratio, germination index, and vigor index after natural aging, and two inbred lines with stronger tolerance to natural aging were identified from the 10 inbred lines studied. In aged seeds, levels of gibberellin, abscisic acid, total protein, total starch, as well as activities of antioxidant enzymes, lipoxygenase, and amylase, and malondialdehyde (MDA) content, exhibited significant differences among inbred lines. Correlation analysis revealed a positive correlation among four seed vigor indices and a highly negative correlation between seed vigor indices and MDA content. Germination ratio, germination index, and vigor index displayed a highly negative correlation with lipoxygenase activity. Furthermore, starch granule decomposition was observed in the endosperm of low-vigor inbred lines, contrary to amylase activity. Thus, this study indicates variations in seed vigor, biochemical indicators, and the ultrastructure of aged sweet corn seeds among different genotypes. Both lower lipoxygenase activity and reduced MDA accumulation contribute to seed resistance to aging.