The Physiological Response Of The Atioxidant System In Leymus Chinensis To Different Alkali-saline Stress

Leymus chinensis is a rhizomatous grass, mainly from36°-62°N and120°-132°E within the broad scope of eco-adaptability, plasticity，resist salt andalkali. L. chinensis is the dominant species in Songnen Plain. The antioxidant enzymeactivities, ascorbic acid (AsA) and glutathione (GSH) contents in the leaves andrhizomes of Leymus chinensis were measured. The antioxidant enzyme includessuperoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbateperoxidase (APX), glutathione reductase(GR), dehydroascorbate reductase(DHAR)and monodehydroascorbate ascorbic acid reductase (MDAR).The experimental results of L. chinensis under different alkali-saline stress inSongnen Plain showed that, with the alkali-saline stress aggravated gradually the SOD,APX, GR, AsA and GSH of leaves and rhizomes increased, the CAT activitydecreased first and then increased, the POD activity increased gradually in May. Andthe DHAR activity of leaves increased under the alkali-saline stress. The DHAR ofrhizomes increased first and then decreased. The MDAR activity of leaves was sameto the DHAR of rhizomes and the MDAR of rhizomes decreased. The activities ofSOD, CAT, POD, APX, GR, DHAR and MDAR in the leaves increased in July. TheAsA content of leaves also increased. The SOD and POD activities of rhizomesincreased at first and then decreased. The activity of CAT, APX, GR, DHAR,MDARincreased gradually. The GSH content of rhizomes decreased at first and thenincreased. The SOD and POD activities changed of a fluctuating, the CAT activitydecreased at first and then increased in September. Except the SOD activity whichdecreased, other antioxidant enzyme activities increased gradually on the whole. TheAsA content of leaves increased on the whole. And the content of rhizomes increasedat first and then decreased. The SOD, CAT, POD, GR of rhizomes was higher thanleaves during the three periods. Both the antioxidant enzyme activities and theantioxidants contents were changed significantly (p <0.05).The experimentalresults of the simulated saline alkali stress showed that theSOD, POD, APX, GR, MDAR activities of leaves increased at first and thendecreased under the alkali-saline stress aggravated gradually. The CAT activity andMDA content increased gradually. In contrast, the DHAR and MDAR activities decreased. The activities of SOD, CAT, POD and the MDA content were higher thanthe control. The gradient from A3to A5, both the APX activity of rhizomes and theGR activity of leaves were higher than the control, the GR activity of rhizomes lowerthan the control and the DHAR, MDAR activities of leaves and rhizomes were lowerthan the control. These results indicated that the antioxidant enzyme activities ofrhizomes were inhibited under the alkali-saline stress. The AsA content of leavesunder the alkali-saline stress compared with the control group A1, the AsA contentfrom A3to A5group was higher and A2was lower. The AsA content of rhizomesincreased first and then decreased, and the content changed same to the leaves. ExceptA2gradient, the AsA content of leaves of other gradients and the control were higherthan the rhizomes. The GSH content of leaves and rhizomes were higher than thecontrol. The GSH content of leaves increased and the rhizomes increased first andthen decreased with the the alkali-saline stress aggravated gradually. The GSH contentof leaves in A5was significant higher than other groups. From A1to A5, the GSHcontent of rhizomes was higher than the leaves.