Modulation of NaCl stress in Capsicum annuum L. seedlings by catechin

Environmental stress, including salinity stress, can cause oxidative damage to plants. We investigated the protective effects of exogenously applied catechin on growth, accumulation of proline, lipid peroxidation and activity of antioxidant enzymes in sweet pepper (Capsicum annuum L. cv. Trim Star) seedlings exposed to salt stress. Salinity stress (at 150 mM NaCl) caused significant inhibition of seedling growth that was significantly mitigated by catechin. The relative water content of shoots decreased under salinity stress but increased with exogenous catechin application. The magnitude of the increase in free proline accumulation was significantly higher in 150 mM NaCl-treated plants than untreated plants but was even higher in the roots of plants treated with 2 mM catechin in addition to 150 mM NaCl. Exogenous catechin treatment had a protective effect on photosynthetic pigment content decrease under saline conditions and resulted in a decrease in lipid peroxidation and increases in ATP and polyphenol content. Salinity stress leads to the accumulation of reactive oxygen species in seedlings and decreased activity of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), ascorbate peroxidases (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2). Among the antioxidant defense enzymes studied here, the magnitude of increase was found to be greater in the NaCl + catechin-treated plants than in the NaCl-treated seedlings. Extracellular application of catechin significantly blocked the inward Na+ and increased the Ca2+ content in roots and shoots. It seems that catechin confers salinity tolerance on sweet pepper seedlings probably through inducing osmoticants and antioxidant enzymes and the balancing of Na+ and K+.

► Most researches noted the antimicrobial activity of catechins.
► This study was the first to demonstrate protection efficiency of catechin.
► Catechin treatment confers antioxidant activity on NaCl-treated sweet pepper plants.
► The polyphenol accumulation capacity participated in salt tolerance of sweet pepper.
► Exogenous antioxidant application is a convenient and effective approach.