Sensitivity and biochemical mechanisms of sunflower genotypes exposed to saline and water stress

Abstract

Crops tolerant to salt and drought stress are an excellent alternative for producers in semi-arid regions. However, it is necessary to select the crops more tolerant and understand their involved mechanisms. We evaluated the effects of salinity and drought on growth, water status, membrane integrity, as well the behavior of organic and inorganic solutes in sunflower genotypes. Greenhouse experiments were performed to evaluate the tolerance of sunflower genotypes (Catissol 01 and Helio 253) to the salt and drought stress. The salt and drought stress were simulated by sodium chloride (NaCl) and polyethylene glycol (PEG 6000), respectively. The treatments with NaCl and PEG 6000 induced adverse changes on the growth, water status and cell membranes of the sunflower plants. Sunflower genotypes are more sensitive to water deficit due to the higher osmotic imbalance. The presence of saline ions minimized damages in sunflowers genotypes caused by lower water potential. The Catissol 01 genotype accumulated Na+ in the stem and roots avoiding translocation to the leaves. Helio 253 showed higher tolerance to the salt and drought stress than Catissol 01. Salinity and drought caused alterations on the carbohydrates and nitrogen compounds of the two sunflower genotypes. Soluble sugars, soluble proteins, free amino acids, and proline participate differently in the osmotic adjustment of the genotypes. The accumulation of soluble sugars, soluble proteins, and proline in the leaves is a mechanism that increases the tolerance to the salt and drought stress in the Helio 253 genotype.