Epinasty promoted by salinity or ethylene is an indicator of salt‐sensitivity in tomatoes

Abstract

Abstract Six genotypes of tomato (Lycopersicon esculentum Mill.) that differ in their salt‐tolerance, were exposed to 200 mol m−3 NaCl for 4 weeks. Seedlings exhibited a marked decline in shoot dry weight accumulation and increased petiolar epinasty after exposure to salinity stress. Ranking accessions on the basis of their relative growth reduction in response to salinity, provided good agreement with the level of epinasty promoted during the salinity treatment. In the absence of salt‐stress, leaf epinasty promoted by exogenous ethylene treatment was found to be a positive indicator of the genotypes incipient salt‐sensitivity. Endogenous ethylene levels in untreated plants were negatively correlated with ethephon‐induced epinasty. Genotypes with normally high endogenous C2H4 levels were less responsive to ethephon treatment and also exhibited greater salt‐tolerance than genotypes with low endogenous C2H4 levels. These observations are consistent with the suggestion that a main feature of adaptation in the genotypes examined may involve modulation of their cellular sensitivity to C2H4. The results indicate that leaf epinasty, whether salt‐ or ethylene‐induced, is a sensitive indicator of salt‐sensitivity. Ethylene‐induced epinasty may, therefore, provide a simple basis upon which to identify and select salt‐tolerant plants.