Heat Shock-Induced Salt Stress Tolerance in Lentil (Lens culinaris Medik.)

Abstract

Soil salinity is a major constraint in crop production. Of the different strategies to cope with salt stress, a cross-tolerance strategy is inexpensive and easy to adopt. In this study, we investigated heat shock-induced salinity tolerance mechanism in lentil (Lens culinaris Medik cv. BARI Lentil-7). Six-day-old seedlings were exposed to 100 mM NaCl with or without 4-h heat shock (HS) (40 ± 1°C) for three days. The results showed that 100 mM NaCl reduced chlorophyll content, caused severe oxidative damage by reducing antioxidants, increased the toxic methylglyoxal (MG) content and disrupted ion homeostasis by increasing Na⁺ in the shoots and decreasing K⁺ in the roots. Heat shock pre-treatment improved the chlorophyll content and reduced oxidative damage by improving reduced ascorbate content, the GSH/GSSG ratio, catalase and ascorbate peroxidase activity under salt stress. Moreover, heat shock reduced the toxic MG content by upregulating glyoxalase system. Heat shock inhibited Na⁺ accumulation in the shoots and K⁺ efflux from the roots, as a result, the Na⁺/K⁺ ratio reduced both in the roots and shoots under salt stress. We further investigated the HS-induced changes in H₂O₂ and MG content. We assumed that the dynamics of H₂O₂ and MG at 1 h intervals during heat shock play a signaling role in activating antioxidant defense and glyoxalase pathway, as a result, plant showed tolerance to salt stress.