Abstract: To identify superior salt-tolerant families of Quercus virginiana, we evaluated the physiological and biochemical characteristics of various families under salt stress by examining the response mechanisms of nonstructural carbohydrate (NSC) content and the stoichiometry of carbon, nitrogen, and phosphorus. The experiment involved three treatments, with 0.4% and 0.8% of soil dry mass as low and moderate salt stress treatments and deionized water as a control. Growth characteristics, antioxidant enzyme activity, osmotic adjustment substance content, chlorophyll fluorescence parameters, as well as the carbon (C), nitrogen (N), and phosphorus (P) content and their stoichiometric ratios of different families were measured. The results showed that salt stress significantly reduced the growth across the four families. The levels of membrane lipid peroxide malondialdehyde, proline content, and antioxidant enzyme activity significantly increased, while soluble protein content markedly decreased. Under salt stress, the actual photosynthetic efficiency of leaves (Y(II)), apparent electron transfer rate (ETR), and photochemical quenching coefficient (q_P) were reduced, whereas the non-photochemical quenching coefficient (q_N) significantly increased. Soluble sugar and NSC content increased, while starch content decreased. The C, N, and P contents of each family exhibited varying degrees of decrease. N∶P ratios ranged from 14 to 16, suggesting that the plants were co-limited by N and P. There were significant or extremely significant correlations among the various indicators. Furthermore, gray correlation analysis identified malondialdehyde, leaf length growth, non-structural carbohydrate, actual photosynthetic efficiency, and N/P ratio as key indicators for assessing salt tolerance. Principal component analysis and a comprehensive evaluation of membership functions both indicated that the salt tolerance order of the four families was as follows: WL1 > WL5 > WL2 > WL3. Notably, the WL1 family exhibited the highest level of salt tolerance and should be prioritized in future promotion trials of salt-tolerant varieties.

Key words: NaCl, physiological characteristics, chlorophyll fluorescence, non-structural carbohydrate, carbon, nitrogen and phosphorus stoichiometric characteristics