Physiological characteristics,gas exchange,and plant ion relations of quinoa to different saline groundwater depths and water salinity

The objective of this study was to investigate the influence of saline groundwater depths (SGDs) (0.3, 0.55, and 0.80 m) with salinity equivalent to irrigation water salinity (WS) and irrigation WS (10, 20, 30, and 40 dS m^?1) on physiological characteristics, gas exchange, and plant ion relations of quinoa in cylindrical lysimeters in greenhouse conditions. Root length density (RLD) in the soil layer close to the saline shallow groundwater decreased. Soil aeration was the key point for reduction in RLD by decreasing SGD that was intensified by the increase in WS. It is concluded that root of quinoa was sensitive to anaerobic soil conditions. Results showed that the mean value of leaf water potential (Ψ) dropped from ?1.53 to ?3.09 MPa by increasing WS from 10 to 40 dS m^?1. Increasing WS from the lowest to the highest level resulted in 48% decrease in leaf photosynthesis rate (A_n). Results revealed that leaf stomatal conductance (g_s) was more sensitive to salinity than A_n. Stomatal closure in quinoa started to occur when the Ψ value fell below approximately ?1.0 MPa. In general, increasing WS from 10 to 40 dS m^?1 resulted in about 4.6-fold, 2.1-fold, and 2.6-fold increase in plant Na⁺, Ca²⁺, and Cl^? concentration, respectively.