Amelioration of high temperature stress by exogenously applied salicylic acid: Genotype‐specific response of physiological traits

In arid and semi‐arid regions of the world, high temperature stress adversely affects growth and development of cool‐season grasses during late spring and summer. Salicylic acid (SA) is one of the endogenous plant growth regulators that plays an important role in the regulation of plant growth and development in response to high temperature stress. The aim of the present study was to assess the effectiveness of SA in alleviating the negative effects of high temperature during the summer in different tall fescue (Festuca arundinacea Schreb.) genotypes under field conditions. Twenty genotypes of tall fescue (selected from a broad native and exotic germplasm) were assessed at field condition for morphological and physiological characteristics during 2016 and 2017 under normal irrigation in the presence of two SA concentrations (0 and 1 mM). High temperature during the summer led to induction of incomplete summer dormancy and depression in summer forage yield. Application of SA decreased the adverse effects of high temperature stress by elevation of photosynthetic pigments, proline accumulation, and increasing nonenzyme and enzymatic antioxidant activities, and could therefore be used to enhance forage yield and heat tolerance in tall fescue genotypes. The genotypes exhibited obvious differences in their response to SA application under the semiarid climate conditions of central Iran. Among the studied genotypes, 3L and 1E were recognized as heat tolerant and stable genotypes that would be preferable for regions with high temperature.