| Seeds are the main reproductive organs of plants.The seed quality usually affects the storage safety and the subsequent seedling cultivation.Toona sinensis(A.Juss.)Roem is an important timber tree species in low mountain,hills and plains of North,East and Central China.It has various economic,such as edible,medicinal,and ornamental values.However,T.sinensis seeds have the characteristic of intolerance to storage.Previous studies on seed vigor of T.sinensis mainly focused on the effect of provenance,storage temperature and water content,plant growth regulators,etc;yet the research on physiological and biochemical changes and aging mechanism of T.sinensis seeds during aging is relatively less.In this study,T.sinensis seeds were used as experimental materials.The artificial accelerated aging treatment was carried out under high temperature(40℃)and high humidity(95%)for 1,2,3,4,5,6,7 and 8 days.In order to analyze the dynamics of seed vigor,seedling morphology,and physiological and biochemical indexes during the artificial aging of T.sinensis seeds,the germination indexes,seedling morphology indexes,relative electrical conductivity,malondialdehyde(MDA)content and antioxidant enzymes activity of T.sinensis seeds under all treatments were measured.This study was expected to explore the aging mechanism of T.sinensis seeds and the physiological and biochemical indicators that can be used to measure the vigor level of T.sinensis seeds.Hopefully,this paper will lay the theoretical foundation for the study of seed vigor restoration and germplasm resources conservation of T.sinensis.The study results were as follows:(1)T.sinensis seeds were less tolerant to high temperature and high humidity.The germination rate,germination index and vigor index of T.sinensis seeds decreased significantly during the aging process and showed a gradually decreasing trend.After 4 days of aging treatment,the seed vigor decreased by about 50%.And after 8 days,the seed vigor was basically zero,therefore,in practice,the storage condition should be kept under low temperature and less moisture.(2)Compared with the germination rate,the germination index and vigor index could better reflect the actual vigor level of T.sinensis seeds.In the early stage of aging,the germination rate decreased slowly,while the germination index and vigor index decreased rapidly.Under the same treatment,the decrease of germination index and vigor index of T.sinensis seeds was higher than that of the germination rate.(3)After aging treatment,the seedling growth of T.sinensis seeds was inhibited;however,the effects of different aging duration on seedling growth were not identical.In the early stage,the root growth of seedlings was mainly affected;whearse in the later stage,the height growth of seedlings was affected more significantly.The seedling height showed a trend of stable at first and then decreasing gradually,while the root length showed a “drop-rise-drop” trend.(4)Membrane lipid peroxidation damaged the biomembrane system,which was one of the important reasons for T.sinensis seed aging.Relative conductivity and MDA content could be used as important indicators to evaluate the vigor of T.sinensis seeds.After aging treatment,the relative conductivity and MDA content of T.sinensis seeds increased significantly,and they showed a gradual rise trend in general.There was a positively correlation(P<0.01)between the two indexes;moreover,they were all negatively correlated(P<0.01)with the seed germination rate,germination index,and vigor index.(5)The imbalance of the seed antioxidant enzyme system was also an important reason for the aging of T.sinensis seeds.After aging treatment,the superoxide dismutase(SOD)activity of T.sinensis seeds showed a “rise-stable-drop” trend;the peroxidase(POD)activity showed “up and down” pattern.SOD activity was negatively correlated with germination rate(P<0.05),germination index(P<0.01)and vigor index(P<0.01);POD activity was highly significantly positively correlated(P<0.01)with all germination indexes,indicating that SOD and POD activity were the suitable indexes to evaluate the vigor of T.sinensis seeds. |
PDF Full Text Request