Effects of Exogenous Tryptophan on Growth and Physiological Characteristics of Tomato Seedlings

Abstract

In order to study the effects of exogenous tryptophan on the growth and physiological characteristics of tomato seedlings, different concentrations (0, 50, 100, 200, and 400 mg/L) of tryptophan solution were sprayed on the leaves. The results showed that the biomass and strong seeding indexes of tomato seedlings under 200 mg/L tryptophan treatment were greater than those of other treatments. With the increase of tryptophan concentration, the chlorophyll and carotenoid contents of leaves showed the trend of increasing first and then decreasing, reaching the maximum at 200 mg/L treatment. The tomato seedlings’ soluble sugar and soluble protein contents were significantly increased by exogenous tryptophan treatment, with the 200 mg/L tryptophan treatment having the highest value. The antioxidant enzyme activities of SOD and POD in tomato leaves of all treatments were increased first and then decreased, reaching the maximum at 200 mg/L treatment, and the lowest MDA content occurred in the 50 mg/L treatment. Taken together, our results showed that 200 mg/L exogenous tryptophan treatment exhibited the most benefits in improving tomato seedlings’ growth and physiological activity.