Effects of the exogenous IAA applications on salt tolerance in tomato (Solanum lycopersicum L.)

In this study, the effectiveness of indole-3-acetic acid (IAA) applications in providing salt stress tolerance in tomato was investigated. TOM-141 (tolerant) and TOM-139 (sensitive) genotypes and AG5668 tomato cultivar were used as materials in the study. For stress plants, salt (200 mM NaCl) stress was initiated at 3 true leaf stages. Control plants were irrigated with nutrient solution. In IAA applications, 0.05, 0.25, 0.50, 0.75, 1.00 and 2.00 mM doses were used together with salt stress, and it was applied as a foliar spray once a week. The end of the experiment, plants were evaluated according to shoot fresh and dry weight, stem length and diameter, leaf number and area, relative water content (YOSI), shoot Na, Cl, K and Ca content, malondialdehyde (MDA), total chlorophyll and carotenoid, total phenolic substance and flavonoid content. Salt stress caused a decrease in plant growth parameters, YOSI, K and Ca ion concentration, total chlorophyll and carotenoid and total flavonoid content in tomato genotypes; Na and Cl ion concentration, MDA and total phenolic substance content increased. On the other and, in IAA applications with salt stress, on average 8-93% in fresh and dry weight; 7-65% in stem length and diameter; 22-329% in leaf number and area, 18-30% in YOSI values; 12-34% in K content; 9-37% in Ca content; 3-125% in total chlorophyll and carotenoid content; 7-107% improvement was achieved in total phenolic substance and flavonoid content compared to salt stress. In addition, Na ion uptake to 10-21% and Cl ion uptake to 13-16% were limited. The increase in MDA content was prevented at the level of 29%. As a result of the study, it was determined that IAA applications improved the negativities caused by salt stress at varying rates and were effective in increasing tolerance, and 0.25 mM and 0.50 mM IAA applications came to the fore in terms of this positive effect among the applications.