Seed priming with H2O2 improves photosynthetic efficiency and biomass production in sunflower plants under salt stress

Salinity commonly affects photosynthesis and crop production worldwide. However, some studies have shown that hydrogen peroxide seed priming can increase the tolerance of plants to salt stress. In this context, this study aimed to test the hypothesis that the H2O2 seed priming can improve photosynthetic efficiency in sunflower plants under salt stress. The experiment was conducted in a completely randomized design, with four replicates. Six treatments were tested: control (deionized water); salt control (100 mM NaCl); 0.1 mM H2O2 (36 h) + 100 mM NaCl; 1 mM H2O2 (24 h) + 100 mM NaCl; 10 mM H2O2 (12 h) + 100 mM NaCl; and 100 mM H2O2 (12 h) + 100 mM NaCl. Compared to the control treatment, leaf, stem and root dry mass of stressed plants showed 73, 76, and 71% reduction, respectively. However, this effect was less pronounced in plants whose seeds were primed with H2O2. After five weeks, H2O2 seed priming increased the CO2 assimilation rate by 26%, instantaneous carboxylation efficiency by 38%, potential quantum yield and quantum yield of photochemical quenching of photosystems II by 22%, electron rate transport by 43%, and the chlorophyll b content by 71%. In addition, it reduced the non-photochemical quenching parameters by 22% compared to plants under salt control treatment.