Nitrogen Modulates the Effects of Short-Term Heat, Drought and Combined Stresses after Anthesis on Photosynthesis, Nitrogen Metabolism, Yield, and Water and Nitrogen Use Efficiency of Wheat

Abstract

More frequent and more intense heat waves and greater drought stress will occur in the future climate environment. Short-term extreme heat and drought stress often occur simultaneously after winter wheat anthesis, which has become the major constraint threatening future wheat yield. In this study, short-term heat, drought and their combination stress were applied to wheat plants after anthesis, and all wheat plants were restored to the outdoor normal temperature and full watering after stress treatment. The aim of the current study was to evaluate the role of nitrogen (N) in modulating the effects of post-anthesis short-term heat, drought and their combination stress on photosynthesis, N metabolism-related enzymes, the accumulation of N and protein and growth, as well as on the yield and water (WUE) and N use efficiency (NUE) of wheat after stress treatment. The results showed that compared with low N application (N1), medium application (N2) enhanced the activities of nitrate reductase (NR) and glutamine synthase (GS) in grains under post-anthesis heat and drought stress alone, which provided a basis for the accumulation of N and protein in grains at the later stage of growth. Under post-anthesis individual stresses, N2 or high application (N3) increased the leaf photosynthetic rate (An), PSII photochemical efficiency and instantaneous WUE compared with N1, whereas these parameters were usually significantly improved by N1 application under post-anthesis combined stress. The positive effect of increased An by N application on growth was well represented in a higher green leaf area, aboveground dry mass and plant height, and the variation in An can be explained more accurately by the N content per unit leaf area. Short-term heat, drought and combined stress after anthesis resulted in a pronounced decrease in yield by reducing grain number per spike and thousand kernel weight. The reduction in NUE under combined stress was higher than that under individual heat and drought stress. Compared with N1, N2 or N3 application significantly prevented the decrease in yield and NUE caused by post-anthesis heat and drought stress alone. However, N1 application was conducive to improving the productivity, WUE and NUE of wheat when exposed to post-anthesis combined stress. The current data indicated that under short-term individual heat and drought stress after anthesis, appropriately increasing N application effectively improved the growth and physiological activity of wheat compared with N1, alleviating the reduction in yield, WUE and NUE. However, under combined stress conditions, reducing N application (N1) may be a suitable strategy to compensate for the decrease in yield, WUE and NUE.

Effects of Straw Return with Nitrogen Fertilizer Reduction on Rice (Oryza sativa L.) Morphology, Photosynthetic Capacity, Yield and Water–Nitrogen Use Efficiency Traits under Different Water Regimes

“…Compared to the CF regime, we also observed an increase in F v /F m , Φ PSII , and qP of CID at the heading stage (Table 2), and a positive correlation with biomass and yield (Figure 8), in agreement with previous studies [55]. The CID regime created alternating wet and dry conditions in rice fields, where the soil transformed between aerobic and anaerobic environments, stimulating the microbial decomposition of straw.…”

Drought-Induced miRNA Expression Correlated with Heavy Metal, Phenolic Acid, and Protein and Nitrogen Levels in Five Chickpea Genotypes

“…Plant phenolic compounds respond to drought stress in various ways depending on factors such as the exposure time and volume of water given to the plant. An increased total content of flavonoids, phenolics, and multiple polyphenolics and increased radical scavenging activity were observed in plants under drought stress. , Caffeic acid levels, for example, do not follow any pattern. The decrease in the protein content can be attributed to a reduction in protein synthesis or an increased rate of protein degradation. , These findings indicate that heavy metal levels are essential in shielding plants from drought stress (Figure ).…”

“…Secondary metabolites are organic products that aid the plant with protection, defense, reproduction, and adaptation to these adverse environments . Flavonoids and phenolic compounds play a critical role in the defense against drought stress. , In crops, drought stress and its interaction with growth and photosynthesis are associated with changes in nitrogen (N) and protein status. , Phenolic compounds are known to be produced in higher amounts under stress conditions as these play a significant role in the growth and development of plants . During their growth and development, plants absorb essential microelements such as copper (Cu), zinc (Zn), and manganese (Mn), as well as some nonessential metal elements like cadmium (Cd), lead (Pb), and mercury (Hg). , …”

“… 16 , 17 In crops, drought stress and its interaction with growth and photosynthesis are associated with changes in nitrogen (N) and protein status. 18 , 19 Phenolic compounds are known to be produced in higher amounts under stress conditions as these play a significant role in the growth and development of plants. 20 During their growth and development, plants absorb essential microelements such as copper (Cu), zinc (Zn), and manganese (Mn), as well as some nonessential metal elements like cadmium (Cd), lead (Pb), and mercury (Hg).…”

Physiological and Molecular Approaches for Developing Thermotolerance in Vegetable Crops: A Growth, Yield and Sustenance Perspective

“…Nitrogen content in the plant measured as nitrate, ammonium ions, and proteins. Besides performing basic roles in plants, its metabolism is also very crucial for heat tolerance because it increases the osmolyte content and antioxidant enzyme activity (Ru et al, 2022 ). Studies have also shown their role in promoting the HSP production (Heckathorn et al, 1996 ).…”