Antioxidation Defence System Of Six Shrubs Under Drought Stress

By using potted-seedlings some kinds of enzyme (SOD, CAT, POD, APX) and metabolites (AsA, GSH, Car) involved with antioxidation defence system of Hedysarum Scoparium Fisch.et Mey, Hedysarum mongolicum Turcz., Caragana korshinskii kom., Atraphaxis bracteata A.los., Buddleja alternifolia Maxim. and Atriplex canescens [Pursh] Nutt seedlings were measured at the different time and under different soil moisture treatments for knowing the response of antioxidation protection system of six shrubs to drought stress. Based on it the adaptive changing rules of six shrubs were discussed. Applying subordinate function values method the antioxidant capabilities of six shrubs were evaluated comprehensively under experimental condition. The main results are as follows:1) The SOD, CAT and POD activities of Hedysarum Scoparium Fisch.et Mey seedlings were increased simultaneously at early period of drought stress. This increased its antioxidant capability. But the changes of APX activity, AsA and GSH contents were not accordant during the whole drought treatmemt. The cycle of Halliwell-AsAda to scavenging H2O2 in chloroplast was not started. But the antioxidant fuctions of themselves were increased relatively at different periods of drought stress. The comprehensive evaluated results of antioxidant capability showed antioxidant capability of Hedysarum Scoparium Fisch.et Mey seedlings was increased on the 30th and 60th day under medium drought treatment and on the 30th day under severe drought treatment.2) On the 30th day under medium drought stress the POD, CAT and APX activities and AsA , GSH contents of Hedysarum mongolicum Turcz. seedlings were increased. The oxygenation injur did not happen on seedlings. During 60th to 90th day the oxygenation injur had happended on seedlings and kept stable. This period the seedlings kept high CAT and APX activities and high contents of ASA and GSH. Under severe drought stress the oxygenation injur had happended on seedlings from 30th day. But till 60th day the oxygenation injur did not keep on increased because the POD, CAT and APX activities of Hedysarum mongolicum Turcz. seedlings heightened and the contents of ASA and GSH were increased. Till 90th day the antioxidation defence mechanism was damaged due to continued drought. The POD,CAT,APX,ASA and GSH of Hedysarum mongolicum Turcz. Seedlings showed important function under drought adversity.3) Under drought stress the SOD activity, AsA, GSH and Car contents of Caragana korshinskii kom. seedlings showed depressed or decreasing firstly. But following the time continued its activity and contents would be increased to or over suitable soil moisture level. This showed the adaptive changing course of Caragana korshinskii kom. seedlings. The comprehensive evaluated results of antioxidant capability showed antioxidant capability of Caragana korshinskii kom. seedlings was under suitable soil moisture level on the 30th and 60th day but over suitable soil moisture level on the 9th under drought treatment4) Under medium drought stress the increases of POD, CAT and APX activities, GSH and Car contents of Atraphaxis bracteata A.los. seedlings were all important approaches of increasing ability of scavenging active oxygen and showed a long duration. Under severe drought stress some approaches of scavenging active oxygen were restrained or destroyed prematurely compared with medium drought stress. For example the CAT and APX activities were decreased respectively on the 30th and 60th day. But new approach of scavenging active oxygen would be increased such as AsA content increase. So whether medium drought stress or severe drought stress the antioxidant capability of Atraphaxis bracteata A.los. seedlings was always keeped at a high level during the whole drought stress.5) Under drought stress the response of antioxidation protection system of Buddleja alternifolia Maxim. seedlings showed a great different because of different stress intensities. Compared with suitable soil moisture control the SOD and CAT activities were increased only on the 90th day and the APX activity, AsA and GSH content always had not sidnificant different on the 30th, 60th and 90th day under medium drought stress. So its antioxidant capability was not increased greatly. Compared with suitable soil moisture control the SOD activity was always increased after the 60th day and the CAT and APX activities, AsA and GSH contents were increased on the 30th, 60th and 90th day under severe drought stress. Its antioxidant capability was increased obviously.6) Under drought stress the SOD, POD, CAT, APX and AsA of Atriplex canescens [Pursh] Nutt seedlings were adjusted to increase activity or content in succession. Its antioxidant capability was increased especialy under medium drought stress. This keeped the balance of active oxygen yielding and scavenging to avoid the cell injured by active oxygen. Under severe drought stress although the antioxidant capability of Atriplex canescens [Pursh] Nutt was increased oxidative damage happened still and was worsened later because of rapid acummulation of active oxygen.