Exogenous IAA Application Enhances Durum Wheat Tolerance to Salinity by Regulating Osmotic Adjustment and Ionic Homeostasis

Abstract

Salinity is one of the major abiotic stresses affecting wheat growth, development, and yield. However, diverse approaches have been adopted to improve plant tolerance and yield under such conditions. In this study, the potential of exogenous indole acetic acid (IAA) application to improve salinity tolerance in durum wheat (Triticum durum Desf.) was tested. Numerous physio-biochemical traits were analyzed at the vegetative stage, and morphometric traits were analyzed at the reproductive stage. The obtained results showed that salt-treated plants exhibited a significant decrease in shoot, root, and whole plant growth, SPAD index, potassium (K), and the quantum yield of PSII, against a significant increase in sodium (Na), proline, and soluble sugar concentrations. Salinity stress also induced early ear desiccation. Although salt-stressed plants sprayed with IAA-did not reach control levels, they showed significant recovery of overall hampered physiological functions and morphometric parameters. Exogenous IAA increased root growth, chlorophyll content, K uptake, PSII efficiency, and soluble sugars, due to improved plant growth supported by enhanced photosynthesis, osmotic adjustment, and ionic compartmentation. Ear maturation, length, and filling, and grains calibre were also improved following exogenous IAA application. Shoot spraying with IAA is an effective treatment to improve wheat tolerance to salinity stress.