Role of L-Tryptophan on the growth and development of sunflower (Helianthus annuus L.) under water stress

Abstract

Water is a significant abiotic stressor that substantially restricts crop yield. Water deficiency impacts the physiological characteristics of plants. The use of the amino acid L-Tryptophan, which functions as an osmolyte, regulates ion transport and modulates stomatal opening, has been shown to mitigate the detrimental effects of water deficiency. This study aimed to assess the impact of L-Tryptophan on the growth and development of sunflowers subjected to water stress during the spring season of 2014 at the Agriculture Research Farm, University College of Agriculture and Environmental Sciences, Department of Agronomy, Islamia University of Bahawalpur, Pakistan. The experiment was structured using a randomized complete block design (RCBD) with a split plot layout. Three concentrations of L-Tryptophan foliar spray (0 mg L^-1, 50 mg L^-1, and 100 mg L^-1) and four lack of water treatment (no water stress, stress from water during the budding phase, water stress during the blooming stage, and water stress during the milking stage) were employed. Results demonstrated that water deficiency considerably affects the leaf surface index, leaf surface duration, crop development rate, net absorption rate, total moisture production, leaf comparative water content, and leaf excised water loss, whereas L-tryptophan treatment greatly improves these parameters. The maximum yield was seen in I1S2 (absence of water stress during milking with 50 mg L^-1 L-TRP foliage application), while in stress treatments, the highest output occurred in I4S3 (water stress during pumping without 100 mg L^-1 L-TRP foliar application).