Evaluation of Growth, Physiological and Photosynthetic Characteristics of Two Spinach Cultivars (Hybrid and Iranian) under Alkaline Water Stress

Alkalinity has destructive effects on plant production. Due to increasing of soil and water alkalinity in the worldwide specially Iran, in this experiment, the effects of alkalinity stress on growth, physiological and photosynthetic parameters was investigated in two cultivars of spinach (‘Barg-Pahn-e-Varamin’ and ‘NARITA’ F1 hybrid). This experiment was carried out during the 2018 as a factorial in a completely randomized design with four replications on the Vali-e-Asr University of Rafsanjan farm. Factors included alkalinity stress at four levels (0, 10, 20, 30 mM sodium bicarbonate) and cultivars at two levels. The results showed that alkalinity stress reduced growth parameters (Shoot and root dry weight, leaf number and leaf area) in both spinach cultivars, but reduced shoot dry weight and leaf area under 30 mM sodium bicarbonate stress in hybrid cultivar was greater than Iranian cultivar. Sodium bicarbonate also reduced pigments, total chlorophyll, SPAD, PI and Fv/Fm indexes and at the level of 30 mM bicarbonate, a 30 percent reduction in photosynthesis rate was observed compared to control plants. As the stress increased, the leaf relative water content decreased and the amount of ion leakage and proline content increased. In Iranian cultivar up to 20 mM level, no significant increase in leaf sodium was observed. The results also showed that in both cultivars, with increasing stress levels, the growth and photosynthetic characteristics of plants were reduced, but it seems that the Iranian cultivar (‘Barg-Pahn-e-Varamin’) is more tolerant than hybrid cultivars according to the evaluated parameters in low concentrations of bicarbonate (10 and 20 mM). In general, this cultivar is more suitable for cultivation in alkaline conditions than hybrid cultivar according growth, physiological and photosynthetic parameters.