Physiological Mechanisms of Exogenous ABA in Alleviating Drought Stress in <i>Nitraria tangutorum</i>

Drought stress caused by continuous global warming poses a severe challenge to the growth and development of <i>Nitraria tangutorum</i>. Abscisic acid has an important regulatory function in the process of plants responding to drought stress. This study took the <i>N. tangutorum</i> seedlings of Zhangye provenance 2-17-16 genealogy as the research object to explore the physiological mechanism of how different concentrations of exogenous ABA alleviate drought damage in <i>N. tangutorum</i>. The results showed that exogenous ABA could promote the growth and increase the leaf relative water content of <i>N. tangutorum</i> seedlings under drought stress. It alleviates the photosynthetic inhibition phenomenon of <i>N. tangutorum</i> seedlings under drought stress by regulating the photoprotective mechanism and energy distribution efficiency of photosystem II. It also alleviates the drought damage of <i>N. tangutorum</i> by increasing the content of osmotic-adjustment substance contents such as soluble sugar, soluble protein, proline, and starch, as well as enhancing the activity of antioxidant enzymes such as POD, SOD, and CAT. The comprehensive analysis showed that 20 μM and 30 μM ABA have the best alleviating effects on the drought damage of <i>N. tangutorum</i> seedlings. This study provides a theoretical basis for the restoration, propagation, and protection of <i>N. tangutorum</i>, and it is of great significance for maintaining the balance and stability of desert ecosystems.