Physiological water strategy of Artemisia ordosica around soil threshold of drought

The mechanism for plants around the soil threshold of drought (close to the soil wilting water content) is a problem that needs to be further explored. In this paper, Artemisia ordosica, which grows in the Tengri Desert, was selected to analyze the changes in the plant water potentials in the soil-plant-atmosphere continuum (SPAC), the water contents in the roots, shoots and leaves of A. ordosica, and the indices in enzymatic and non-enzymatic systems. Based on the statistics, we discussed the water physiology mechanism around the soil drought threshold. The results show that, around the soil drought threshold, besides absorbing and transporting water, the roots could serve as temporary water reservoirs that enable A. ordosica to continue to transport the SPAC water and survive severe drought. As drought becomes more severe, the activity of superoxide dismutase (SOD) and catalase (CAT) increases and they have significant correlations with the tissue water content. The activity of peroxidase (POD) decreases and it has no significant correlation with the tissue water content. During daytime, when temperature is high, the soluble sugar does not participate in the osmotic adjustment but eliminate the active oxygen free radicals. Thus, around the soil threshold of drought, A. ordosica maintains a physiological water metabolism by harmo-nizing water itself and eliminate the active oxygen and the free radicals by the joint efforts of enzymatic and non-enzymatic systems.