Due to impact on the pH of growing medium, water alkalinity is the most important parameter determining water quality. Thus, to investigate the effect of sodium bicarbonate on strawberry, an experiment was carried out considering two factors including sodium bicarbonate at three levels (0, 15 and 30mM) and seven strawberry cultivars (Albion, SanAndreas, Paros, Aromas, Diamante, QueenElisa, and Camarosa). Sodium bicarbonate increased the EC and pH of growing medium in all studied cultivars. The results showed that vegetative and reproductive growth, chlorophyll fluorescence parameters, and relative water content of leaves diminished with an increase in sodium bicarbonate concentration and Camarosa cultivar was more sensitive than other cultivars. The maximal quantum yield of PSII photochemistry (Fv/Fm), PI, Fv, Fm, Area, Fv/Fo, RC/ABS and (1-Vj)/Vj parameters declined in all cultivars with increasing sodium bicarbonate, especially in Camarosa cultivar. Fo parameter rose with increasing sodium bicarbonate, with the greatest increase being related to Camarosa cultivar at 30mM sodium bicarbonate. The chemical/physical parameters of fruit diminished by bicarbonate, with the San Andreas and Diamante showing the highest and lowest fruit EC, pH, and TSS, respectively. Under stress conditions, Paros cultivar showed the minimum changes in fruit color parameters. The results showed that Paros and Camarosa are the most tolerant and sensitive cultivars to alkalinity stress, respectively. Also, chlorophyll fluorescence parameters, especially PI and Fo, are suitable indices for bicarbonate stress evaluation in strawberry cultivars and secondary alkalinity induced stress like salinity and drought stress may cause a change in PI and Fo.
