Abstract:

Salt stress has a significant inhibitory effect on plant growth and development， while an appropriate concentration of abscisic acid （ABA） can effectively alleviate the damage caused by salt stress. In this study， Atraphaxis bracteata seedlings were used as the experimental material， and a pot experiment was conducted to investigate the effects of applying different concentrations （2.5， 5， 7.5， 10， 15 mg·L^-1， with 0 as CK） of exogenous ABA on the growth and physiological responses of various organs of A. bracteata seedlings under 150 mmol·L^-1 NaCl stress. The goal was to identify the suitable concentration of ABA that can promote A. bracteata growth even under salt stress. The results showed that low-concentration abscisic acid alleviated salt stress damage by reducing malondialdehyde content. Under the 5 mg·L^-1 treatment， the malondialdehyde content in all organs of A. bracteata was the lowest， with a 38.46% decrease in roots， 34.78% in stems， and 26.25% in leaves compared to CK. In contrast， high-concentration abscisic acid treatment significantly increased soluble sugar and starch content. At 15 mg·L^-1， the soluble sugar content in roots increased by 61.19% compared to CK， while the levels in stems and leaves reached their highest. The starch content in roots increased by 36.01%， in stems by 48.61%， and in leaves by 51.48%. This indicates that low-concentration abscisic acid （2.5， 5 mg·L^-1） effectively mitigates salt stress damage in A. bracteata， whereas high-concentration abscisic acid （15 mg·L^-1） reduces its mitigating capacity and even inhibits seedling growth. Principal component analysis showed that malondialdehyde content， dry and fresh weight， proline content， starch content， and superoxide dismutase activity can serve as the main indicators for evaluating the alleviating effect of exogenous ABA on salt stress in A. bracteata. Using membership functions to perform a comprehensive evaluation of 10 indicators in three organs of the seedlings showed that a 5 mg·L^-1 exogenous ABA solution had the highest average membership degree in each organ， at 0.97， 0.93， and 0.73 respectively， indicating that this concentration of exogenous ABA had the strongest regulatory ability on salt tolerance in A. bracteata. These research results provide a theoretical basis for salt-tolerant cultivation of A. bracteata and have important implications for improving desert environments and promoting sustainable agricultural development.

Key words: Atraphaxis bracteata, abscisic acid, salt stress, physiological index, principal component analysis