RESPONSES OF CHLOROPLASTIC ANTIOXIDANT DEFENSE AND PHOTOSYNTHESIS CHARACTERISTICS OF HEDYSARUM SCOPARIUM AND ATRAPHAXIS BRACTEATA UNDER DROUGHT STRESS

A water-controlled pot-culture experiment was conducted to clarify the mechanism of the photosystem adaptability of Hedysarum scoparium and Atraphaxis bracteata to drought stress, with the responses of the chloroplastic antioxidant defense system and characteristic parameters of the light/CO2 response curves of these shrubs detected. The results indicated that (1) for H scoparium, its chloroplastic SOD and DHAR activities significantly increased by 233% and 52% in light drought (LD) soil, its SOD and DHAR activities and AsA and GSH contents increased by 209%, 37%, 96% and 100% in moderate drought (MD) soil, and its SOD, GR and DHAR activities and AsA, GSH and Car contents significantly increased by 57%, 51%, 37%, 42%, 63% and 179%, but the accumulation of H2O2 and MDA (54.9% and 146.5%) was also observed in the serious drought (SD) soil. For A. bracteata, its chloroplastic GR and DHAR activities and AsA content significantly decreased by 20%, 57% and 19% in LD soil with the accumulation of MDA (214%) simultaneously observed. In the MD and SD soils, the SOD activity and AsA, GSH and Car contents significantly increased by 63%, 40%, 32% and 135%, while the accumulation of H2O2 and MDA was also observed (194% and 145-245%). (2) The P-nmax, A QY and TPU of H. scoparium significantly decreased by 22%, 19% and 13% in MD soil, while the P-nmax, AQY, V-cmax, J(max), TPU and R-1 significantly decreased by 52%, 19%, 31%, 21%, 26% and 16% in SD soil. However, Gm significantly increased by 130% in SD soil. ForA. bracteata, its Pnmax, AQY and LSP significantly decreased by 50%, 19% and 35-41% in all types of drought soil. In conclusion, in the revegetation of desert regions, H. scoparium can be planted in LD and MD conditions, while A. bracteata can only be planted in LD conditions.