IMPACT OF SALINE-ALKALI STRESS ON THE ACCUMULATION OF SOLIDS IN TOMATO FRUITS

Abstract

Growing of tomato plants in saline conditions, having high rhizospheric EC, is often reported with high solid content in fruits. However, saline-alkali stress conditions, having high rhizospheric pH as well as high EC, have never been studied to evaluate its impact on the solid content of tomato fruits. In this study, we investigated the impact of saline-alkali stress (0, 30, 60, 90, and 120 mM NaHCO3) on the accumulation of solids in tomato fruits. Addition of sodium bicarbonate (NaHCO3) to plants highly increased pH as well as EC of the soil leachate in 90 and 120 mM NaHCO3 treatments in comparison to control treatment. Saline-alkali stress treatments did not influence the fruit dry weight, nonetheless, the content of fruit dry matter was increased significantly from 6.5% at control to 8.5% at 90 and 120 mM treatments. The content of soluble sugar was increased to 3% in 90 mM treatment in comparison to control (2%), owing to significant accumulation of hexose as well as sucrose in ripe fruits. In addition to carbohydrates, saline-alkali stress influenced the accumulation of organic acids in fruits, as well. Citric acid, being the major acid, showed positive correlation with the salt concentration, and was significantly high at stress treatments of higher than 30 mM. These results suggested that salinealkali stress conditions, in spite of high pH, can increase the contents of fruit solids in tomato, as is usually observed in saline stress conditions.