Drought stress is one of the most serious environmental stress factor constraining crop production across the globe. Among cereals, wheat grains are very sensitive to drought as a small degree of stress can affect the enzymatic system. This study aimed to investigate whether nitrogen and pre-anthesis drought priming could enhance the action of major regulatory enzymes involved in starch accumulation and protein synthesis in bread wheat (Triticum aestivum L.). For this purpose, cultivars YM-158 (medium gluten) and YM-22 (low gluten) were grown in rain-controlled conditions under two nitrogen levels, that is, N180 (N1) and N300 (N2). Drought priming was applied at the jointing stage and drought stress was applied 7 days after anthesis.Drought stress reduced starch content but enhanced protein content in grains. N2 and primed plants kept higher contents of nonstructural carbohydrates, fructans, and sucrose; with higher activity of sucrose-phosphate synthase in flag leaves. Furthermore, N2 and priming treatments showed higher sink ability to develop grains by showing higher sucrose-to-starch conversion activities of adenosine diphosphateglucose pyrophosphorylase, uridine diphosphate glucose pyrophosphorylase, sucrosesynthase, soluble-starch synthase, starch branching enzyme, and granule-bound starch synthase as compared to N1 and non-primed treatments. The application of N2 and primed treatment showed a greater ability to maintain grain filling in both cultivars as compared to N1 and non-primed crops. Our study suggested that high nitrogen has the potential to enhance the effect of pre-drought priming to change source-sink relationships and grain yield of wheat under drought stress during the filling process.
| INTRODUCTIONDrought is a misfortune for agriculture, livestock, and humanity alike (FAO, 2018). Severe climate events are expected to rise in the coming years due to global warming and will directly threaten food security around the globe (Zaid et al., 2021;Zeeshan et al., 2021Zeeshan et al., , 2022.Climate change not only worsens droughts by making them more frequent, longer, and more severe, but also makes the world more parched and hotter (FAO, 2019). It has become a big hurdle for farmers to produce crops of good quality with high yields. Nearly 61% of the total viable land for crop production received precipitation of less than 500 mm in 2009 (Hejnak et al., 2009), the level below the limit for productive dryland agriculture (Jensen et al., 2006).Wheat being extremely susceptible to drought stress, particularly during its post-anthesis and reproductive phases, experienced extensive yield damage mainly attributed to limited photosynthesis and
