Hydraulic characteristics and carbon metabolism of Lycium chinense Miller and Tamarix chinensis Lour. under saline-alkali stress

Saline-alkali stress is a significant abiotic stress affecting plant growth worldwide. However, the hydraulic characteristics and carbon metabolism features of plants responding to saline-alkali stress remain poorly understood. Two saline-alkali tolerant plants, wolfberry (Lycium chinense Miller) and Chinese tamarisk (Tamarix chinensis Lour.), were examined to explore their water-carbon responses to saline-alkali stress under different salinity-alkalinity levels. Branch water potential, percentage loss of conductivity (PLC), stomatal conductance, net photosynthetic rate, nonstructural carbohydrate (NSC) concentration, and growth status of the plants were measured. Results showed that severe saline-alkali stress significantly reduced the predawn and midday water potential, photosynthetic rate, and PLC of both species, with T. chinensis exhibiting a more severe reduction in photosynthetic rate, stomatal conductance, and branch PLC than L. chinense. Strong saline-alkali stress also significantly reduced NSC concentration of all tissues in L. chinense; however, the NSC concentration in the aerial parts in T. chinensis was significantly increased, whereas the root NSC concentration was significantly decreased. Both species coped with saline-alkali stress using different strategies. Strong stomatal regulation of L. chinense was beneficial for the maintenance of hydraulic architecture, but constrained carbon uptake. Weak stomatal regulation of T. chinensis affected hydraulic architecture, but was advantageous for the maintenance of the carbon balance.