Salt tolerance induced by hydrogen peroxide priming on seed is related to improvement of ion homeostasis and antioxidative defense in sunflower plants

Salt-induced redox and ion imbalance may lead to increased oxidative stress and impair the plant growth. However, among the many reactive oxygen species (ROS) produced under stress, hydrogen peroxide (H2O2) plays a central role in several signal transduction pathways triggering a series of physiological mechanisms and increase plant tolerance to salt stress. Thus, this study aimed to evaluate the changes in the balance of inorganic and organic solutes induced by seed priming with H2O2 in leaves and roots of sunflower plants grown under salt stress. In this study, six treatments were tested: T1 - control (absence of NaCl and absence of H2O2); T2 - salt control (presence of 100 mM NaCl and absence of H2O2); T3 - 100 mM H2O2 (12 h) + 100 mM NaCl; T4 - 10 mM H2O2 (12 h) + 100 mM NaCl; T5 - 1 mM H2O2 (24 h) + 100 mM NaCl; T6 - 0.1 mM H2O2 (36 h) + 100 mM NaCl. Our results show that, the role of H2O2 in increase of the salt tolerance is directly associated with reduction on Na+ (on average 46%) and Cl- (on average 24%) contents in the leaves, besides a positive regulation of K+ and NO3 (-) absorption (for three harvests). In addition, H2O2 priming also decreased the oxidative damage, mainly by increasing the activity of catalase enzyme (CAT) in leaves (on average 49% at 2(nd) and 3(rd) harvests) and roots (on average 39% at 3(rd) harvest).