Mohammad Javad Ahmadi-Lahijani - Assistant Professor, Department of Agrotechnology, Ferdowsi University of Mashhad, Iran
Jafar Nabati - Assistant Professor, Research Center of Plant Sciences, Ferdowsi University of Mashhad, Iran
Morteza Goldani - Associate Professor, Department of Agrotechnology, Ferdowsi University of Mashhad, Iran
Ahmad Nezami - Professor, Department of Agrotechnology, Ferdowsi University of Mashhad, Iran

The increasing salinity of water and soil as one of the consequences of climate change has adversely affected the plant functions and reduced plant productivity, threatening future food security. Hence, we hypothesis different pH levels (unadjusted as control (~8.5-9), 5.5, and 4.5) would mitigate the salinity effects on tomato plants (cv. Mobil). Generally, increasing salinity stress and pH levels decreased stomatal conductance (gs) and leaf SPAD; however, the greatest gs was observed in pH 4.5 grown plants under control conditions (31% greater than the control pH). Stomatal conductance and leaf osmotic potential were negatively correlated. The highest leaf osmotic potential was observed at 56 days after stress (DAS) at pH 5.5. Leaf relative water content (RWC) was decreased by increasing salinity intensity in low-pH-grown plants. Plants grown at pH 5.5 had the most significant fruit fresh weight and plant dry weight. It seems that although salinity reduced the plant performance, lowering the rhizosphere pH could positively mitigate the diminishing effects of salinity on the plant yield.

Fruit weight, Hydroponic culture, Osmotic potential, Rhizosphere acidity, Survival.