Effects of tryptophan application on drought stress in pepper

ABSTRACT; Drought is one of the most important abiotic stress factors that have negative effects on plants. Plants encounter many stress conditions throughout their lives and have developed tolerance mechanisms to combat the negative effects of stress. They usually use plant growth hormones known as phytohormones to cope with stress. Tryptophan is one of the most important plant growth hormones. Tryptophan (Trp), which is a naturally produced amino acid in some plants, was applied 0, 0.25, 0.50, 0.75, 1 mM from the root to reduce the effects of drought stress to which pepper seedlings exposed in our study and to ensure the return of the plants with re-irrigation. Plants subjected to free drought, and samples were collected when drought symptoms observed. After the stress treatments completed, the plants irrigated with 100 ml of water and samples taken from the plants. The control group consisted of Trp-treated plants and plants without drought stress. Chlorophyll, carotenoid, hydrogen peroxide (H2O2), malondialdehyde (MDA), proline, protein, and enzyme activities determined in the samples. In this study, Trp applications showed positive effects in terms of proline, MDA, H2O2, and enzyme activities. When the total chlorophyll and carotenoid contents were analyzed, no statistically significant effect of Trp application was observed. When the effects of Trp application on protein, SOD, and CAT antioxidant enzyme activities were examined, protein contents decreased with Trp application, whereas SOD and CAT values increased.