Studies On Physio-biochemical Changes, DNA Damages And Invigoration In Artificial Aged Rice Seeds

The study was performed to explore the physio-biochemical changes and DNA damages during artificial accelerated aging of rice cultivar,117954and Zheyou12. Aged seeds of different vigor were obtained by accelerated aging at43℃and100%relative humidity for3,6or9days, then the physiological and biochemical changes, cellular ultrastructure and ISSR fingerprints were studied. Finally the wet-dry treatment and sand priming treatments were used to restore the aged seed vigour. The research on the mechanism of seed deterioration will help to provide instruction for the seed storage. The results are as follows:1. With prolonging of aging time, germination energy, germination percentage and germination index had a decling tendency. There were significant differences in above three parameters after aged for6d compared with un-aged seeds. Aged seeds could extend the increased metabolism time (IMT) and relative germination time (RGT), while shorten the oxygen metabolism rate (OMR). There was a negative relation between electric conductivity, the content of MDA, nucleotide and seed vigour, which showed seed aging had an obvious effect on the cell membranous system. POD (peroxidase), SOD (superoxide dismutase), CAT (catalase) activities reduced as the aging time increased. Ultrastructure damage was observed after aging, mitochondria was deformed and disintegrated, and the lipid bodies ultimately merged into lipid cellulite in aged seed.2. POD of117954and POD, SOD, CAT, APX (ascorbic acid reductase) of Zheyou12from the seedling had no difference with the un-aged control, which indicated that protective enzymes could recover to a certain extent during the seedling period. As the aging period extended, the regularity degree of rice descended, meanwhile many shorter seedlings appeared at aged9d compared with the control.3. DNA was extracted from aged seeds by CTAB method, then ISSR marker was used to analyze DNA change. The result showed that bands ranged600-700bp disappeared compared with the control by primer UBC886, and bands disappeared at350-400bp compared with the control by primer UBC811in both two cultivars. DNA bands reduced when the aging time prolonged, and even disappeared.4. Wet-dry treatment and sand priming obviously increased the germination energy, germination percentage and germination index, shortened the mean germination time of aged seeds. Both treatments were simple and could invigoration rice aged seed vigour.