Responses Of The Seedlings Of Gleditsia Sinensis Lam., Diospyros Lotus L. And Cercis Chinensis Bunge To Salt-drought Intercross Stresses

The potted one-year-old seedlings of Gleditsia sinensis Lam.,Diospyros lotus L. and Cercis chinensis Bunge were tested to study their changes in growth, physiological and biochemical indexes in order to analyze their responses to salt-drough intercross stresses. The intercross adaptation was also studied to salt-drough intercross stresses and this will provide theoretic basis for selecting and breeding for superior varieties. The test results are as the followings:The growth characteristics of those three species seedlings had been more adversely affected as the intercross stresses intensified: the height growth was inhibited and the biomass was decreased, but the ratio of root to crown was increased significantly and the resistance was enhanced by partitioning of more substance to root. The time of injury symptom on Gleditsia sinensis Lam. was appeared later than that of Diospyros lotus L. and Cercis chinensis Bunge, whose injury was reached up to 4 grade and the survival ratio was decreased significantly in 21th day. As the stresses intensified and continued, the water-holding capacities of Gleditsia sinensis Lam. appeared first a declining and then increasing trend. However the trend of Diospyros lotus L. and Cercis chinensis Bunge was opposite. Moderate intercross stresses were benifit for enhancing the water-holding capacities.The activities of SOD,CAT,POD of Gleditsia sinensis Lam. were kept on first an increasing trend under moderate intercross stresses and then declining as the stresses intensified, which indicated that the eliminating function of free radical was already weakened; the activities of Diospyros lotus L. and Cercis chinensis Bunge appeared first an increasing and then a declining trend, which showed a short-term adaptation and kept at a high level under light intercross stresses. The correlation analysis indicated that POD,CAT were the main enzymes for Gleditsia sinensis Lam. to eliminate the extra free radical while CAT was the only main enzyme to eliminate the extra free radical at the late stage of treatment. And for Diospyros lotus L. and Cercis chinensis Bunge, CAT was the main enzyme and both of SOD and CAT worked together after 21 days of treatment to keep the balance for producing and eliminating the free radical.The cell membrane conductivities and MDA contents of these three species seedlings were lower than check under light intercross stresses of drought and salt, but they increased gradually as the stresses intensified and continued. The correlation analysis indicated that there were negative correlations between enzymes and the cell membrane conductivities, MDA contents; and there were basically positive correlation between osmoregulation subtances and the cell membrane conductivities, MDA contents partly. There were significant positive correlation between the cell membrane conductivities and MDA contents in the course of the stresses.For Gleditsia sinensis Lam., the contents of proline, soluble suger and soluble protein were kept on an increasing trend and showed an obvious salt- drought intercross resistance; for Diospyros lotus L. and Cercis chinensis Bunge, they appeared first an increasing and then a declining trend, but they were all kept at a high level at the end of the treatment. It indicated that they played an active role on resistance of the seedlings. In the course of treatment, the proline of Gleditsia sinensis Lam. and Cercis chinensis Bunge played the role by changing the quantity and metabolic pathway of other substances. Soluble suger and soluble protein increased significantly. The correlation analysis indicated that in the course of the stresses, there were significant positive correlation among the osmoregulation subtances, which indicated that the osmoregulation subtances worked together and played an effective regulating role for these three species seedlings. Under the moderate intercross stresses of drought and salt,the partitioning of Na+ of these three species seedlings in root,stem and leaf was as followings: root>stem>leaf, and the contents of Na+ were increased in stem and leaf as the stresses intensified. The seedlings of Cercis chinensis Bunge was evidently damaged. The ratio of K+ and Na+ in root,stem and leaf kept at a relatively high level and the sequence was rootT2C>T3B>T2D>T1B>T1C>T1D>T3C>T3D; for Diospyros lotus L., the grade sequence was T1C>T1B>T1D>T2B>T2C>T3B>T2D>T3C>T3D; for Cercis chinensis Bunge, the grade sequence was T1B> T1C> T1D>T2B> T3B>T2C>T2D>T3C>T3D. The resistance ability of these three species seedlings was Gleditsia sinensis Lam.>Diospyros lotus L.>Cercis chinensis Bunge.