Effect Of Low Temperature On Some Physiological Characters Of Hypocotyle And Cotyledon In Mung Bean And Broad Bean

Physiological characters of both hypocotyle and cotyledon in mung bean (Phaseolus radiatus Linn.) and broad bean (Viciafaba L.) were researched under different low temperature. Systemic study on Phaseolus radiatus Linn, and Viciafaba L, were carried on membrane leakage, membrane-lipid peroxidation, defensive enzyme and ultrastructure of hypocotyle cells. The main purpose is to disclose the physiology acclimation mechanisms to cold.(1) The contents of membrane leakage in both hypocotyle and cotyledon in mung bean and broad bean increased with temperature decreasing. The increased amplitude in mung bean was larger than that in broad bean, and it was larger in hypocotyle than that in cotyledon. Compared with control groups, membrane leakage in hypocotyle of mung bean which was treated under 10 had significant deviation. However, after the varieties were stressed under persistent temperature at 16 or 10, there was no significant effect on membrane leakage in mung bean and broad bean.(2) Under different temperature,the contents of MDA in hypocotyle was always higher than that in cotyledon, and MDA contents in mung bean had always shown more variation than that in broad bean. It showed an upward tendency with temperature decreasing, but decreased in low amplitude both in mung bean and in broad bean at 16 stress. The effect of 10 and 16 low temperature on contents of MDA in hypocotyle and cotyledon of mung bean was prominent,and it had significant difference with control groups at C.01 level, but there was no difference about MDA contents in hypocotyle and cotyledon of broad bean after stressed.(3) Low temperature had different effect on activities of three defensive enzymes of SOD, POD and CAT. Activity of CAT decreased in both of cold-resistant broad bean and cold-sensitive mung bean under 16 stress. It increased under 10stress, and increased more largely in mung bean than that in broad bean. There were different POD activities in different resistant plants,although in different tissue of same plant POD activities also gavedifferent response to low temperature. Except for activity of POD in hypocotyle of mung bean increasing, it usually decreased in cotyledon both of mung bean and of broad bean and hypocotyle of broad bean while temperature decreasing; However,activity of SOD often enhanced with temperature decreasing.and moreover,it was more sensitive to low temperature in broad bean than that in mung bean.SOD activity in cold-resistant broad bean increased more significantly. In our research,we also found that activity of SOD had made a regular change after stored at 4 in rridge,moreover, its change had some correlation with that stressed at 4.(4) The common effects of 10 low temperature on ultrastructure of hypocotyle cells in both mung bean and broad bean were that the number of mitochondria increased and gathered together, plasma membrane were invaginated, vacuolar membrane were infolded and made up of one new structure which looked like little vacuole.But they also made different response to low temperature at 10,for example, the number of starch grains in plastid increased in hypocotyle cells of mung bean,while decreased significantly in hypocotyle cells of broad bean;And their difference also showed that hypocotyle cells of broad bean had plasmolization and form of some plastid in it were changed,while a number of cells in hypocotyle of mung bean appeared degradated.