Physiological and biochemical studies on drought tolerance of wheat plants by application of amino acids and yeast extract

Wheat (Triticum aestivum L.) is one of the most important cereal crops grown in the world. Drought is a worldwide problem, constraining global crop production seriously and recent global climate change has made this situation more serious. Two experiments (pots and field) were performed to investigate the effect of foliar spray with some biostimulants (amino acids 1.5 and 3 ml/L or yeast 3 and 6 g/L) to reduce hazards of drought stress (irrigation after the depletion of 65% and 80% of available soil water) on bread wheat (Sakha 94 cv.). The obtained results revealed that all studied characters of growth, relative water content (RWC), photosynthetic pigments, total soluble sugars (TSS), total carbohydrates (TC), total free amino acids (TAA), enzymes activities, minerals (NPK% and uptakes), yield and its attributes and grain quality were negatively affected by lower water supplies, meanwhile a significant increase was obtained in leaf water deficit (LWD), osmotic potential (OP), total phenols (TP) and proline content. The maximum decrease was recorded under high level of water stress (W2) compared to optimum level of water supply (W0). Application of amino acids and yeast extract significantly increased all measurement studied with exception of leaf water deficit, osmotic potential and proline content characters in favor of yeast application at a rate of 6 g/L compared to untreated plants in the two seasons. The interaction between the tested water stress and biostimulants was found to be significant for most characters of physiological traits and yield and its components. Also it was noticed that application of yeast (6 g/L) under normal water supply gave the best results of all studied characters. Also, it could be recommended that application of natural substances led to overcome the deleterious effect of drought and consequently resulted in improved the productivity of wheat and its grain quality.