Mechanical wounding of leaf midrib and lamina elicits differential biochemical response and mitigates salinity induced damage in tomato

Abstract: The objective of the study was to evaluate biochemical response to two different types of wounding damage in leaves of tomato (Lycopersicon esculentum Mill.) and also to investigate the influence of pre-wounding on subsequent salt stress exposure. Wounding experiment was performed by small punctures either on the midrib or leaf lamina. Results showed that damage by wounding elicited a rapid increase in H₂O₂ levels within the first few hours of wound stress. H₂O₂ levels, total phenolic and flavonoid levels were significantly higher in midrib damage than either the lamina damage or control conditions. Wounding pre-treatment reduced the toxic effects of NaCl stress in plants. Alleviation of salt induced damage was greater in midrib cuts through the stabilization of relative water content and also an increase in antioxidant scavenging activity. These results confirm that wounding pre-treatment induced cross-tolerance to salinity stress in tomato plants. It is suggested that an early and significantly elevated generation of H₂O₂ with local midrib injury could induce a priming response systemically, thereby providing protection to the subsequent salt stress injury.