Effect of Saline Stress on Plant Growth and Leaf Antioxidant Activity of Wild and Cherry Cropped Tomato

Salinity is one of the main factors limiting plant growth, productivity and quality of crops, with more than 20% of irrigated land affected by salt. This study was conducted to elucidate the effect of saline stress (NaCl) on growth and antioxidant enzyme activity in leaves of two tomato genotypes: wild (Solanum chilense Dun.) and cherry (Solanum lycopersicum L. var. cerasiforme). Both tomato species were grown in a greenhouse and irrigated with water at four levels of salinity: 0, 40, 80 and 160 mM NaCl, representing four different saline treatments. Plant growth (fresh weight of aerial biomass and height per plant) and xylem water potential (Psi(x)) were recorded simultaneously with leaf enzymatic activity. Leaves of wild and cherry tomato plants were analyzed for the enzymatic activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX). Although cherry tomato plants showed an increment of fresh mass at relatively medium salinity treatments (40 and 80 mM), in general fresh mass was strongly reduced in both genotypes under severe saline stress (160 mM). However, fresh mass of wild tomato plants were more affected than cherry genotypes. Under saline stress conditions, Psi(x) and water content (WC, %) were not significantly affected. Finally, the paper also shows preliminary results of the effect of salinity on the main antioxidant enzymatic activities in order to understand mechanisms of reactive oxygen species free radical detoxification within the plant.