Drought resistance in plants is controlled by multiple genes. To identify the genes that mediate drought stress responses and to assess the associated metabolic pathways in the desert shrub Nitraria tangutorum, we conducted a transcriptome analysis of plants under control (maximum field capacity) and drought (20% of the maximum field capacity) conditions. We analyzed differentially expressed genes (DEGs) of N. tangutorum and their enrichment in the KEGG metabolic pathways database, and explored the molecular biological mechanisms underlying the answer to its drought tolerance. Between the control and drought groups, 119 classified metabolic pathways annotated 3047 DEGs in the KEGG database. For drought tolerance, nitrate reductase (NR) gene expression was downregulated, indicating that NR activity was decreased to improve drought tolerance. In ammonium assimilation, drought stress inhibited glutamine formation. Protochlorophyllide reductase (1.3.1.33) expression was upregulated to promote chlorophyll a synthesis, whereas divinyl reductase (1.3.1.75) expression was downregulated to inhibit chlorophyll-ester a synthesis. The expression of the chlorophyll synthase (2.5.1.62) gene was downregulated, which affected the synthesis of chlorophyll a and b. Overall, drought stress appeared to improve the ability to convert chlorophyll b into chlorophyll a. Our data serve as a theoretical foundation for further elucidating the growth regulatory mechanism of desert xerophytes, thereby facilitating the development and cultivation of new, drought-resistant genotypes for the purpose of improving desert ecosystems.

Seed germination and subsequent changes in Chamecytisus palmensis were studied under water limiting conditions, imposed by increasing concentrations of polyethylene glycol (PEG-6000) (0, 5, 10, 15, 20, 25, and 30%). Six water stress conditions (< −0.20, −0.20, −0.40, −0.60, −0.8, and −1.20 MPa) were created in the laboratory in a completely randomized design. The results showed that PEG-simulated drought stress had an inhibitory and lag effect on seed germination of C. palmensis. Seed germination was completely inhibited under the drought stress of 30% (−1.20 MPa). Similar to the seed germination, the growth of radicles and hypocotyls after seed germination was also restricted by PEG-simulated drought stress, especially when water potential was lower than −0.12 MPa (25%). In the same way, the ratio of radicles and hypocotyls significantly decreased with the increase of PEG concentrations, demonstrating strong adaptability to drought stress. Moreover, the decline of radicles and hypocotyls lead to a decrease in the number of root hairs. This would seriously affect the water absorption ability of the young roots. It was concluded that drought stress might be one of the causes for obstructed natural regeneration of C. palmensis plantations on sandy land.

Wind erosion is an important part of environmental change research and represents a key destabilizing factor in arid and semi-arid ecosystems. The desert-oasis ecotone is an ecological barrier that protects oases from sandstorms. Nitraria tangutorum nebkhas help mitigate the impacts of wind erosion in desert-oasis ecotones. This study analyzed the relationship between vegetation coverage and soil grain size in a desert-oasis ecotone along the southeastern margin of the Tengger Desert. The results showed that the soil grain size distributions for nebkhas consisted primarily of fine, medium and very fine sand. The measured proportion of fine sand increased as vegetation coverage increased. The trailing edge of leeward slope and leading edge of windward slope positions contained higher proportions of coarse-grained material relative to other slope positions. Samples collected 0-5 cm depth contained higher proportions of fine-grained material than those collected at 5-10 cm depth. The average particle size ranges for nebkhas with low, medium, and high vegetation coverage were 1.644-2.430 φ, 1.601-2.911 φ, and 1.752-2.871 φ, respectively. Soil sorting degree was categorized as medium. Skewness values were extremely negative, negative, and positive respectively, and kurtosis levels were medium, narrow and medium, respectively. Samples collected from windward slope positions gave higher mean grain size values than those measured from samples collected along leeward slope and the top positions.