Drought and Salinity Impacts on Bread Wheat in a Hydroponic Culture: A Physiological Comparison

Drought and salinity are two major abiotic stresses, similarly and/or differently affecting physiological processes of wheat. The aim of this study was to evaluate and compare the impacts of drought and salinity on wheat. A pot experiment was conducted as completely randomized design with three replications in the research greenhouse of Yasouj University in 2015. Treatments included different levels of salinity and drought with the same osmotic potentials (-2.47, -4.94 and -7.42 bar) and a control. Salinity and drought were imposed with NaCl and PEG 6000 in a Hogland medium, respectively. Results showed that by increasing drought and salinity treatments, relative water cotent and cell membrane stability were decreased but malondialdehyde (MDA) increased. The effect of PEG drought stress on these traits was more than that of NaCl stress. Increasing drought and salinity stresses significantly increased leaf proline, total soluble sugars, and glycinebetaine content, however, this increase was higher for salinity. Fv/Fm was equally affected by salinity and drought, decreasing by both stresses. By raising stress levels, chlorophyll a decreased but chlorophyll b and carotenoid content increased. In general, we found that wheat could tolerate acceptable salinity levels better than drought, by accumulation of osmolytes and more sustained absorption of water and also reducing the MDA production under salinity conditions.