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Heat stress during the grain filling is one of most critical factors impacting grain yield in winter wheat. In a two-year field experiment, we studied the effects of 24-Epicastasterone and KH2PO4 on heat-stressed wheat applied during different times. A completely randomized block design was used with three reagents, that is, 24-Epicastasterone, KH2PO4 and H2O and three spraying times, that is, pre-heat, under-heat and post-heat. Two cultivars, that is, Huaimai 33 and Annong 0711 were subjected to a 7 d post-flowering heat stress using plastic tents. Our study suggests that greater grain weight in heat-stressed plants was achieved through sustaining leaf greenness and higher assimilates supplies to grains. When heat-stressed plants sprayed either with 24-Epicastasterone or KH2PO4 could sustain a relatively higher leaf photosynthetic capacity by up-regulating antioxidant enzymes with reduced damage on lipid membranes and leaf chlorophyll. We also found that KH2PO4 was relatively more effective in improving leaf physiology and grain yield of heat-stressed plants than 24-Epicastasterone. Further analysis showed that pre-heat or post-heat was more pronounced in protecting plants from heat injury than spraying the plants under heat stress. Thus, spraying KH2PO4 either prior to or post stress incidence is recommended to protect wheat crops from terminal heat stress. [ABSTRACT FROM AUTHOR]

As one of the most important wheat-producing areas in China, wheat is prone to heat stress during the grain filling period in the Huang-Huai-Hai Plain (3HP), which lowers yields and degrades the grain quality of wheat. To assess the effects of spraying potassium dihydrogen phosphate (KH2PO4) on the physiological traits in flag leaves and grain yield (GY) and quality under heat stress during the filling period, we conducted a two-year field experiment in the winter wheat growing seasons of 2020–2022. In this study, spraying water combined with heat stress (HT), 0.3% KH2PO4 (KDP), and 0.3% KH2PO4 combined with heat stress (PHT) were designed, and spraying water alone was used as a control (CK). The dates for the spraying were the third and eleventh day after anthesis, and a plastic film shed was used to impose heat stress on the wheat plants during the grain filling period. The results showed that spraying KH2PO4 significantly improved the chlorophyll content and net photosynthesis rate (Pn) in flag leaves compared with the non-sprayed treatments. Compared with CK, the Pn in HT decreased by 8.97% after heat stress, while Pn in PHT decreased by 7.44% compared to that of KDP. The activities of superoxide dismutase, catalase, and peroxidase in flag leaves were significantly reduced when the wheat was subjected to heat stress, while malonaldehyde content increased, and the enzyme activities were significantly enhanced when KH2PO4 was sprayed. Heat stress significantly decreased the contribution rate of dry matter accumulation (DM) after anthesis of wheat to grain (CRAA), whereas spraying KH2PO4 significantly increased the CRAA and harvest index. At maturity, the DM in CK was significantly higher than that in HT, KDP was significantly higher than PHT, and KDP had the highest DM. Compared with CK, the GY in KDP significantly increased by 9.85% over the two years, while the GY in HT decreased by 11.44% compared with that of CK, and the GY in PHT decreased by 6.31% compared to that of KDP. Spraying KH2PO4 after anthesis primarily helped GY by maintaining a high thousand grain weight to lessen the negative effects of heat stress on wheat. Moreover, heat stress significantly reduced protein concentration, wet gluten content, dough development time, and hardness index in grains of mature, while spraying KH2PO4 maintained a sufficient grain quality under the conditions of achieving higher yields. Overall, spraying KH2PO4 after anthesis could enhance the heat stress resistance of wheat and maintain the photosynthetic capacity of flag leaves, ensuring the dry matter production and reducing the negative effects on grain yield and quality in the 3HP. [ABSTRACT FROM AUTHOR]

We conducted a two-year field experiment on winter wheat (Triticum aestivum L.) from 2016–2018 to compare the effects of reducing nitrogen application rate in spring under three irrigation methods on grain yield (GY), water and nitrogen use efficiency in the North China Plain (NCP). Across the two years, GY of conventional irrigation (CI), micro-sprinkling irrigation (SI) and drip irrigation (DI) decreased by 6.35%, 9.84% and 6.83%, respectively, in the reduced nitrogen application rate (N45) than the recommended nitrogen application rate (N90). However, micro-irrigation (SI and DI) significantly increased GY relative to CI under the same nitrogen application rate, and no significant difference was observed in GY between SI and DI under N45, while SI obtained the highest GY under N90. The difference among different treatments in GY was mainly due to the variation in grain weight. The seasonal evapotranspiration (ET) in N45 was decreased more significantly than N90, and there was no significantly difference in ET among different irrigation methods under N45, but micro-irrigation significantly decreased the ET relative to CI under N90. Micro-irrigation significantly improved water use efficiency (WUE) compared to CI at the same nitrogen application rate. Under N45, compared with CI, WUE in SI and DI increased by 9.09% and 4.70%, respectively; however, the WUE increased by 15.9% and 7.23%, respectively, under N90. Reducing nitrogen application rate did not have a significant impact on WUE under CI, but it did have a substantial negative impact on SI and DI. Nitrogen accumulation in wheat plants at maturity (NAM) in N45 deceased significantly compared with N90 under the same irrigation method. Compared with CI under the same nitrogen application rate, micro-irrigation treatments significantly increased NAM, while SI was the largest. In comparison to N90, under three irrigation methods, N45 significantly increased nitrogen fertilizer use efficiency (NfUE). The highest NfUE was attained in SI, followed by DI, while CI was the lowest. Moreover, N45 significantly decreased soil NO3−-N accumulation (SNC) in three irrigation methods, and micro-irrigation significantly decreased the SNC in deep soil layers compared with CI when nitrogen is applied at the same level. Overall, micro-irrigation with a reduced nitrogen application rate in spring can achieve a relatively higher production of winter wheat while increasing the use efficiency of water and nitrogen and reducing soil NO3−-N leaching into deep soil layers in the NCP. [ABSTRACT FROM AUTHOR]

Low-temperature stress has become an important abiotic factor affecting high and stable wheat production. Therefore, it is necessary to take appropriate measures to enhance low-temperature tolerance in wheat. A pot experiment was carried out using Yannong19 (YN19, a cold-tolerant cultivar) and Xinmai26 (XM26, a cold-sensitive cultivar). We employed traditional phosphorus application (TPA, i.e., R1) and optimized phosphorus application (OPA, i.e., R2) methods. Plants undertook chilling (T1 at 4 °C) and freezing treatment (T2 at −4 °C) as well as ambient temperature (CK at 11 °C) during the anther differentiation period to investigate the effects of OPA and TPA on photosynthetic parameters and the accumulation and distribution of dry matter. The net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of flag leaves decreased in low-temperature treatments, whereas intercellular carbon dioxide concentration (Ci) increased. Compared with R1CK, Pn in R1T1 and R1T2 treatments was reduced by 26.8% and 42.2% in YN19 and 34.2% and 54.7% in XM26, respectively. In contrast, it increased by 6.5%, 8.9% and 12.7% in YN19 and 7.7%, 15.6% and 22.6% in XM26 for R2CK, R2T1 and R2T2 treatments, respectively, under OPA compared with TPA at the same temperature treatments. Moreover, low-temperature stress reduced dry matter accumulation at the reproductive growth stage. OPA increased dry matter accumulation of vegetative organs after the flowering stage and promoted the transportation of assimilates to grains. Hence, the grain number per spike (GNPS), 1000-grain weight (TGW) and yield per plant (YPP) increased. The low-temperature treatments of T1 and T2 caused yield losses of 24.1~64.1%, and the yield increased by 8.6~20.5% under OPA treatments among the two wheat cultivars. In brief, OPA enhances low-temperature tolerance in wheat, effectively improves wheat architecture and photosynthesis, increases GNPS and TGW and ultimately lessens yield losses. [ABSTRACT FROM AUTHOR]

Climate change has caused frequent extreme low-temperature events to threaten global food security. Spring low-temperature stress is one of the major limiting factors for high and stable yields of wheat. We used two wheat varieties differing in spring cold-sensitivity (cold-tolerant variety Yannong 19 and cold-sensitive variety Xinmai 26) to examine the effects of low-temperature stress during the anther differentiation period on wheat photosynthetic performance and spike-setting characteristics. Low-temperature stress was simulated in a climate box at −2 °C, 0 °C or 2 °C (night) and 15 °C (day) for 24 h, 48 h or 72 h. With the extension of the treatment time and the decrease of temperature, the photosynthetic rate, stomatal conductance and transpiration rate of wheat leaves gradually decreased. All treatments except −2 °C for 72 h recovered slowly within 7–15 days after treatment. Low-temperature stress greatly reduced grains per spikelet, 1000-grain weight and yield per plant. By analyzing the spikelets in different stalk locations (upper, middle and lower), we found that the number of upper spikelets was significantly less than lower and middle spikelets after low-temperature stress. The sterile grain of upper spikelets (Xinmai 26, for example) can reach 100% at −2 °C for 48 h and 72 h, and the yield loss rate was 90.52% at 2 °C for 24 h, which was much higher than for the lower spikelets (60.73%) and middle spikelets (50.94%). Overall, these findings suggest that low-temperature stress during the anther differentiation period alters the photosynthetic activity involved in the accumulation of dry matter in wheat, which leads to delaying young spike growth, especially for upper spikelets, and ultimately in a decrease in yield. [ABSTRACT FROM AUTHOR]

In the southern Huang-Huai-Hai (HHH) region, China, maize production is frequently threatened by waterlogging at the seedling stage and by drought at the big flare stage. A two-year field experiment was performed to explore whether subsoiling (SS) in the winter wheat season could improve the photosynthetic capacity and increase the water use efficiency (WUE) of summer maize using the variety, Luyu9105. A split design was adopted in the experiment. The main plots used tillage practices, including SS and rotary tillage (RT). The subplots consisted of two irrigation methods, i.e., applied supplemental irrigation at the big flare stage (I) and no irrigation at the big flare stage (NI). The results showed that the SS treatment significantly increased soil water content (SWC) in the 40–60 cm soil layer. The SS treatment improved green leaf area index (gLAI) by 15.1%–30.2%, and enhanced the ear-leaf net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (ci) and transpiration rate (Tr), and was accompanied by an increase in the grain-filling duration (T) by 5 days and the mean grain-filling rate (Va). The SS treatment decreased the stomatal limitation (Ls), indicating that RT treatment, which was under lower SWC, led to a decrease in Pn. Applied supplemental irrigation under RT treatment was able to compensate for the growth of leaves, but could not reverse the decreasing trend in the gLAI. Ultimately, the SS treatment improved WUE by 9.1%–9.9%, and increased grain yields by 10.0%–29.3%. Therefore, this study showed that in the southern Huang-Huai-Hai Plain, which has a yellow cinnamon soil type, the practice of SS can improve the photosynthetic characteristics of leaves and WUE of rainfed summer maize. [ABSTRACT FROM AUTHOR]

Aims: Drought events during the seedling stage of winter wheat are increasing in Huaibei Plain of China due to global warming, which lowers seedling quality and reduces crop productivity. This study aimed to explore the effect of irrigation methods and topsoil compaction on the seedling growth in this region.We conducted a two-year filed experiment to evaluate the effect of three irrigation practices and topsoil compaction on the shoot and root growth of seedlings. The irrigation methods include rain-fed (RI), traditional flood irrigation (TI) and micro-sprinkling irrigation (MI). Topsoil compaction after wheat sowing was used under each irrigation method (RC, TC and MC). Various above-ground of plant, root traits and physiological data, and the dynamic of soil water content, were recorded.The results demonstrated that MI maintained the highest water content in 0–20 cm soil profile at overwintering stage compared to TI, and TI was significantly higher than RI. MI had higher dry matter accumulation, the number of tillers and roots than TI and RI due to it obtained the highest leaf area index, chlorophyll content, root density and activity, while RI was the lowest levels. The relative growth rate, net assimilation rate and crop growth rate of seedlings were improved in MI than those of TI and RI. Topsoil compaction greatly promoted the growth of seedlings in RI at overwintering stage, and increased the dry matter accumulation in TI.Micro-sprinkling irrigation and topsoil compaction can be used as effective measure to promote the growth of wheat seedling and improve its quality by increasing leaf production and strengthening the root system in the Huaibei Plain region.Methods: Drought events during the seedling stage of winter wheat are increasing in Huaibei Plain of China due to global warming, which lowers seedling quality and reduces crop productivity. This study aimed to explore the effect of irrigation methods and topsoil compaction on the seedling growth in this region.We conducted a two-year filed experiment to evaluate the effect of three irrigation practices and topsoil compaction on the shoot and root growth of seedlings. The irrigation methods include rain-fed (RI), traditional flood irrigation (TI) and micro-sprinkling irrigation (MI). Topsoil compaction after wheat sowing was used under each irrigation method (RC, TC and MC). Various above-ground of plant, root traits and physiological data, and the dynamic of soil water content, were recorded.The results demonstrated that MI maintained the highest water content in 0–20 cm soil profile at overwintering stage compared to TI, and TI was significantly higher than RI. MI had higher dry matter accumulation, the number of tillers and roots than TI and RI due to it obtained the highest leaf area index, chlorophyll content, root density and activity, while RI was the lowest levels. The relative growth rate, net assimilation rate and crop growth rate of seedlings were improved in MI than those of TI and RI. Topsoil compaction greatly promoted the growth of seedlings in RI at overwintering stage, and increased the dry matter accumulation in TI.Micro-sprinkling irrigation and topsoil compaction can be used as effective measure to promote the growth of wheat seedling and improve its quality by increasing leaf production and strengthening the root system in the Huaibei Plain region.Results: Drought events during the seedling stage of winter wheat are increasing in Huaibei Plain of China due to global warming, which lowers seedling quality and reduces crop productivity. This study aimed to explore the effect of irrigation methods and topsoil compaction on the seedling growth in this region.We conducted a two-year filed experiment to evaluate the effect of three irrigation practices and topsoil compaction on the shoot and root growth of seedlings. The irrigation methods include rain-fed (RI), traditional flood irrigation (TI) and micro-sprinkling irrigation (MI). Topsoil compaction after wheat sowing was used under each irrigation method (RC, TC and MC). Various above-ground of plant, root traits and physiological data, and the dynamic of soil water content, were recorded.The results demonstrated that MI maintained the highest water content in 0–20 cm soil profile at overwintering stage compared to TI, and TI was significantly higher than RI. MI had higher dry matter accumulation, the number of tillers and roots than TI and RI due to it obtained the highest leaf area index, chlorophyll content, root density and activity, while RI was the lowest levels. The relative growth rate, net assimilation rate and crop growth rate of seedlings were improved in MI than those of TI and RI. Topsoil compaction greatly promoted the growth of seedlings in RI at overwintering stage, and increased the dry matter accumulation in TI.Micro-sprinkling irrigation and topsoil compaction can be used as effective measure to promote the growth of wheat seedling and improve its quality by increasing leaf production and strengthening the root system in the Huaibei Plain region.Conclusion: Drought events during the seedling stage of winter wheat are increasing in Huaibei Plain of China due to global warming, which lowers seedling quality and reduces crop productivity. This study aimed to explore the effect of irrigation methods and topsoil compaction on the seedling growth in this region.We conducted a two-year filed experiment to evaluate the effect of three irrigation practices and topsoil compaction on the shoot and root growth of seedlings. The irrigation methods include rain-fed (RI), traditional flood irrigation (TI) and micro-sprinkling irrigation (MI). Topsoil compaction after wheat sowing was used under each irrigation method (RC, TC and MC). Various above-ground of plant, root traits and physiological data, and the dynamic of soil water content, were recorded.The results demonstrated that MI maintained the highest water content in 0–20 cm soil profile at overwintering stage compared to TI, and TI was significantly higher than RI. MI had higher dry matter accumulation, the number of tillers and roots than TI and RI due to it obtained the highest leaf area index, chlorophyll content, root density and activity, while RI was the lowest levels. The relative growth rate, net assimilation rate and crop growth rate of seedlings were improved in MI than those of TI and RI. Topsoil compaction greatly promoted the growth of seedlings in RI at overwintering stage, and increased the dry matter accumulation in TI.Micro-sprinkling irrigation and topsoil compaction can be used as effective measure to promote the growth of wheat seedling and improve its quality by increasing leaf production and strengthening the root system in the Huaibei Plain region. [ABSTRACT FROM AUTHOR]