The availability of water is considered as one of the most essential abiotic factor required for plant growth and development and necessary for plant cell turgidity which is associated with numerous plant functions [1–3]. Water scarcity affects several physiological and biochemical processes in plants [4] and deficiency of water within the plant body has broadly spoke to reduce crop yield than any other environmental factor such as water logging and high or low temperature stress [1, 5]. The sensitivity to any biotic and/or abiotic stress differ with the stage of plant growth, for example, drought near the beginning of grain filling stage had marks reduction in grain yield through less number of endosperm cells and sink ability which reduce the dry matter accumulation and assimilate supply. Drought is a big worldwide problem, which is a potential risk for food security in sustainable agriculture [6, 7].
Stage specific water conditions are most important for a good crop performance. Sufficient water supply at or after anthesis stage not only increases photosynthetic rate but also increases grain filling period [8], which consequently increases final grain yield up to 70 to 90% (Inoue et al., 2004). Drought stress at anthesis stage lessens the pollination which results in fewer grains per spike and ultimately reduces the grain yield of the crop [9, 10]. Jeyazsri et al. (2021) indicated grain filling stage in cereals as one of the most sensitive growth stage under drought stress. Different studies on wheat and the other crops have shown that during grain filling stage of plant water scarcity significantly affects the grain weight due to early senescence [12, 13]. The stress response can also vary depending on the developmental stage during which a plant is subjected to stress [14, 15]. A study showed that the effects of drought on water relations and yield at different growth stages and were studied two cultivars by withholding water stress at tillering, anthesis and at both stages, simultaneously and found decrease in water relation parameters, growth and yield components [13, 16]. Drought stress at anthesis cause reduced in pollination and consequently formed less number of grains per spike and kernel weight [17, 18]. Adequate water supply at or after anthesis growth stage not only increases net photosynthetic rate in leaves but also enhance the grain filling period [19].
Drought resistant varieties have more ability to transport pre-anthesis assimilates to fill their grains than that of sensitive varieties. [11] reported grain filling stage in cereals as one of the most sensitive growth stage under drought stress condition. Different studies on wheat and the other crops have shown that during grain filling stage, plant water stress significantly affects the grain weight due to early senescence [20]. Wheat morphological characters such as root length, tiller, number of spikes per m2, number of grains per spike, fertile tillers per plant, 1000- grain weight, peduncle length, spike weight, stem weight and grain weight per spike are affected due to shortage of water in the soil [18, 21]. The water scarcity causes average yield loss of 17 to 70% in grain yield. Early or late season water stress could have highest yield reduction. On the whole, drought stress decreases plant growth and development, and also changes carbon and nitrogen metabolic activities, finally the productivity of crop [22, 23].
Silicon (Si) is the second most plentiful element after oxygen on the surface of earth’s crust and in soil. However, its concentration in soil solution ranges from 0.0004 to 2 mmol dm− 3 and in plant tissues ranges from 0.1 to 10% on the dry weight basis depending on the plant species [7, 24, 25]. Beside the macro and micro nutrients which are essential for plant growth, silicon also enhance the yield and physiological processes such as cell wall rigidity, reduce transpiration, inspire antioxidants, decrease electrolyte leakage and enzymes activation of the crop plants [7, 26–28]. Silicon fertilization may increase and sustain crop productivity of different crops especially under unfavorable conditions. Application of silicon as a fertilizer has been reported beneficial element for stressed plants [29, 30]. Among other possible mechanisms its accumulation in leaves increases vigor and stiffness of cell wall which result in demise of transpiration from cuticle and, uptake and translocation of lethal salts and metal ions from roots to shoots [31, 32]. The seed priming with silicon is an effective method for enhancing the drought tolerance in wheat through improving its antioxidant defense system which ultimately lead to increasing the yield of wheat plant [33, 34]. The present study, therefore, was planned with the objective to determine the effects of water limited stress on growth and yield of wheat grown and to evaluate appropriate time and method of exogenously applied Si for alleviating the adverse effects of water deficit stress in wheat genotypes.