Promotional activity of indole acetic acid and naphthalene acetic acid on growth and photosynthetic pigments of Solanum lycopersicon (tomato) under salinity stress

Abstract

Excessive salt in the soil leads to a series of physiological and biochemical metabolic disorders in plants. Application of bioregulators to alleviate salinity stress can be an economic and safe alternative to environment. We have previously reported that the bioregulators, indole-3-acetic acid (IAA) and naphthalene acetic acid (NAA) enhanced antioxidant enzyme activity and mineral content of salt – stressed tomato. The present study examined the effects of these bioregulators on growth characteristics and photosynthetic pigments of tomato under salinity stress. Presowing treatment of seeds of two tomato genotypes, UC 82B and Tropimech with three concentrations of IAA and NAA were done for 24 hours. Seeds from each treatment were sown in polyethylene bags containing 10kg saline soil portions (0. 100, 200 mM NaCl) in a screen house and replicated four times in a randomized block design. The 150 mg·L-1 IAA concentration significantly increased (p < 0.05) leaf area, fresh weight, and dry weight compared to the 0 mM NaCl control. The 50 mg·L-1 concentration of IAA and 200 mM NaCl significantly increased (p < 0.05) chlorophyll a content in genotype UC 82B and the chlorophyll b content was increased due to treatment with 100 mg·L-1 IAA at 100 mM NaCl. The 100 and 150 mg·L-1 concentrations of NAA at 100 and 200 mM NaCl produced the highest increase in levels of chlorophyll b and carotenoids, respectively. Treatment with these bioregulators alleviated inhibitory effects of salt stress on tomato by enhancing some growth parameters and photosynthetic pigments.