Dynamic Changes in Plant Resource Use Efficiencies and Their Primary Influence Mechanisms in a Typical Desert Shrub Community

Water use strategies of Nitraria tangutorum in the lake-basin region of the Badain Jaran Desert

Information regarding plant water-use strategies is essential for understanding the hydrological processes and plant survival adaptation mechanisms in desert lake basin regions. To examine the water use strategies of plants in desert lake basin areas, water uptake patterns, water use efficiency, and water potential of Nitraria tangutorum were investigated at different distances from the lake duringhe growing seasons in the lake basin regions of the Badain Jaran Desert. The results indicate that N. tangutorum primarily absorbed groundwater in May (63.8%) and August (53.5%), relied on deep soil water in June (75.1%), and uniformly absorbed soil water from different layers in July. These observations could be explained by periodic fluctuations in the groundwater level and the consequent decrease in soil water availability, as well as plant root adjustments. As soil water availability decreases, N. tangutorum adapts to water variation by increasing its water use efficiency (WUE) and reducing its leaf water potential (Ψ). With intensified water stress, N. tangutorum gradually shifted from adventurous anisohydric regulation to conservative isohydric regulation. Thus, N. tangutorum responds to diverse degrees of environmental changes by altering its water-use strategy. A better understanding of the adaptive water use strategies developed by desert plants under varying water availability conditions provides insight into the diversity of species' reactions to long-term drought and quantifies the hydrological cycle of desert ecosystems against the background of worldwide climate warming.

Improved Tolerance of Artemisia ordosica to Drought Stress via Dark Septate Endophyte (DSE) Symbiosis

Dark septate endophytes (DSEs) usually colonize plant roots, especially in stress environments. However, their relationship with plants ranges from beneficial to harmful and has remained largely uncharacterized. In the present study, 14 DSE species grouped into 11 genera were isolated from the roots of a desert plant, Artemisia ordosica, which is widely distributed in northwest China. Three dominant DSE species—Paraphoma chrysanthemicola (Pc), Alternaria chartarum (Ac), and Acrocalymma vagum (Av)—were selected and tested for their resistance to drought in vitro. Furthermore, we characterized the responses of A. ordosica under drought conditions in relation to the presence of these DSEs following inoculation. The results showed that all three strains grew well under in vitro drought stress, and the biomass of Ac and Av was significantly higher than that of the unstressed control. The effects of DSE inoculation on the growth of A. ordosica under drought stress varied according to the different DSE species but were generally beneficial. Under drought stress, Av and Pc promoted plant growth, antioxidant enzyme activity, and root development of the hosts. The Ac strain conferred obvious positive effects on the antioxidant enzyme activity of the hosts. In general, Av and Pc demonstrated better application potential for improving the drought resistance of A. ordosica.