A Differential Phytohormone Profile in the Aerial Part and Roots as a Response to Water Stress Underlying Morphophysiological and Biochemical Changes in Two Inbred Sunflower Lines at Early Growth Stage

Abstract

Water stress is a primary abiotic stress that produces several morphological, physiological, biochemical and molecular alterations, which afect crop productivity. The aim of the present study was to evaluate and compare morphophysiological and biochemical characteristics and the hormone profles of two sunfower inbred lines (C803 and R461-4) in response to moderate water stress at the early vegetative growth (V2) stage. Sunfower seedlings of C803 and R461-4 inbred lines obtained in pots flled with sand moistened to 60% feld capacity were watered with (1) Hoagland’s solution (control) or (2) mannitol 400 mM (moderate water stress) to feld capacity on the fourth day after sowing. At V2, the seedlings were harvested and sectioned into the aerial part and roots. The parameters recorded for the analyses included the aerial part and root length, fresh and dry weight, leaf area and expansion rate, stomatal conductance, osmotic potential, phytohormones and total soluble carbohydrates. Among these parameters, the leaf area and stomatal conductance were the most afected by water stress. Abscisic acid and salicylic acid showed signifcant increases in the aerial part of water-stressed seedlings, while abscisic acid was the most abundant phytohormone in the roots. In addition, 28-Homocastasterone was the brassinosteroid with higher levels in both lines. This is the frst report of teasterone in the sunfower. Finally, total soluble carbohydrates increased upon stressful conditions. Altogether, the water stress led to diferent parameter alterations dependent on the inbred line and its diferent sensitivity to water stress.