The impact of global warming on crop growth periods and yields has been evaluated by using crop models, which need to provide various kinds of input datasets and estimate numerous parameters before simulation. Direct studies on the changes of climatic factors on the observed crop growth and yield could provide a more simple and intuitive way for assessing the impact of climate change on crop production. In this study, four cultivars which were planted over more than 15 years in eight test stations in the Northern Winter Wheat Region of China were selected to investigate the relationships between growth periods, grain yields, yield components and temperatures. It was found that average temperatures and heat degree-days (HDD) during the winter wheat growing seasons tended to increase over time series at most study sites. The length of growth period and growing degree days (GDD) were not fixed for a given cultivar among different years and locations, and the variation on the periods from sowing to jointing was relatively greater than in the other periods. The increasing temperature mainly shortened the periods from sowing to jointing and jointing to anthesis, which led to the decrease in entire growth periods. Positive relationships between spike number, grain number per spike, grain yields and average temperatures were identified in the Northern Winter Wheat Region of China. The grain yield in the study area increased by 406.3 kg ha⁻¹ for each 1 °C increase in average temperature. Further, although the positive relationship between grain yield and HDD was found in our study, the heat stress did not lead to the wheat yield decline in the study region. Temperature is a major determinant of wheat growth and development, the average temperature and the frequency of heat stresses are projected to increase in the future, so understanding the effect of temperature on wheat production and adopting appropriate adaptation are required for the implementation of food security policies.

Global warming can have detrimental effects on crop production formation, but the effect of low-temperature stress on crop quality should not be ignored. Wheat is one of the main grain crops in the world, and the quality of wheat is directly related to human health. The nutritional importance of wheat in the human diet necessitates pursuing a study to collect detailed and accurate knowledge of the amino acid composition of wheat proteins under low-temperature conditions. To better understand the effect of low temperature on the composition of amino acids in mature wheat, we conducted a two-year low-temperature-controlled wheat pot experiment in artificial climate chambers with two different wheat cultivars at four low-temperature intensities during the jointing, booting, and both jointing and booting stages. Our results suggest that the contents of total amino acids, essential amino acids, and nonessential amino acids for the cold-sensitive wheat cultivar (Yangmai16) increased under the low-temperature treatments, while the contents of the cold-tolerant cultivar (Xumai30) decreased when low-temperature was applied during the jointing and double (both jointing and booting) stages. Through the amino acid score (AAS), we found that the first limiting amino acid was Lys, while the second limiting amino acid varied among Ile, Met + Cys, and Val after the low-temperature treatments. Comparing the amino acid ratio coefficients (RCs), we found that Leu and Thr in wheat grains were close to the standard protein after the low-temperature treatments, while Phe and Tyr were in a surplus, and the other essential amino acids did not meet the standard. Thus, to improve the protein quality of wheat, protective measures should be taken when low temperatures occur.

Introduction: The nutritional value of wheat is important to human health. Despite minerals being essential nutrients for the human body, they are often neglected in consideration of the nutritional quality of cereal grains. Extreme low-temperature events have become more frequent due to the current environmental unpredictability, and it is yet unknown how the mineral components in grains are affected by low temperature.Methods: To provide valuable information for enhancing the nutritional quality of wheat under potential climatic conditions, we treated different cold-sensitive wheat cultivars at four low-temperature levels during the individual and combined stages of jointing and booting in controlled-environment phytotrons. Results and Discussion: In general, the contents of P, K, Ca, and Zn in the cold-sensitive cultivar (Yangmai16) and K in the cold-tolerant cultivar (Xumai30) were enhanced by low temperature. However, the accumulation of minerals in mature grains was reduced under low-temperature treatment, except for P, Ca, and Zn in Yangmai16. In addition, the mineral content and accumulation in Yangmai16 (except for Fe) were more susceptible to low temperature during the combined stages, while the mineral content and accumulation of K, Fe, and Zn in Xumai30 were more susceptible to low temperature during the booting stage. Moreover, Yangmai16 under extremely low temperatures (T3 and T4) during booting and Xumai30 under all low-temperature treatments during the combined stages had lower comprehensive evaluation values. These findings offer a crucial reference for enhancing the nutritional quality of wheat grains under climate change.

Extreme temperature events as a consequence of global climate change result in a significant decline in rice yield. A two year phytotron experiment was conducted using three temperature levels and two heating durations to compare the effects of heat stress at booting (BT), flowering (FL), and combined (BT + FL) stages on rice yield and yield components. Compared with T₁ (T_mean of 27 °C), heat stress at BT + FL and BT stages produced more regenerated tillers and compensated more for yield loss than heat stress at FL. Heat stress at BT + FL stages alleviated spikelet sterility and yield loss of original tillers compared to heat stress at FL. The greater variation of yield per plant (YPP) under heat stress at flowering as compared to BT and BT + FL stages was accompanied by a higher decrease in spikelet fertility, while, at BT and BT + FL stages, spikelet number per plant and 1000-grain weight also contributed well to variation in yield. Furthermore, heat stress during BT and BT + FL stages caused a significant decline in spikelet fertility of the upper part of panicles, followed by middle and lower parts, while heat stress at the FL stage responded inversely. For every 1 °C day increase in heat degree days at BT, FL, and BT + FL stages, YPP_O (only original tillers) declined by 2.9%, 2.5%, and 6.0%, and YPP_T (including original + regenerated tillers) decreased by 5.8%, 2.7%, and 2.2%, respectively. The projected alleviation effects under BT + FL stages of heat stress in contrast to single-stage heat stress would help to accurately estimate rice yield under extreme temperature events, as well as to develop a heat-tolerant rice cultivar.

Extreme temperature events as a consequence of global climate change result in a significant decline in rice production. A two-year phytotron experiment was conducted using three temperature levels and two heating durations to compare the effects of heat stress at booting, flowering, and combined (booting + flowering) stages on the production of photosynthates and yield formation. The results showed that high temperature had a significant negative effect on mean net assimilation rate (MNAR), harvest index (HI), and grain yield per plant (YPP), and a significant positive effect under treatment T₃ on mean leaf area index (MLAI) and duration of photosynthesis (DOP), and no significant effect on biomass per plant at maturity (BPP_M), except at the flowering stage. Negative linear relationships between heat degree days (HDD) and MNAR, HI, and YPP were observed. Conversely, HDD showed positive linear relationships with MLAI and DOP. In addition, BPP_M also showed a positive relationship with HDD, except at flowering, for both cultivars and Wuyunjing-24 at combined stages. The variation of YPP in both cultivars was mainly attributed to HI compared to BPP_M. However, for biomass, from the first day of high-temperature treatment to maturity (BPP_T-M), the main change was caused by MNAR followed by DOP and then MLAI. The projected alleviation effects of multiple heat stress at combined stages compared to single-stage heat stress would help to understand and evaluate rice yield formation and screening of heat-tolerant rice cultivars under current scenarios of high temperature during the rice-growing season.

Rice production is threatened by climate change, particularly heat stress (HS). Nonstructural carbohydrates (NSCs) remobilization is a key physiological mechanism that allows rice plants to cope with HS. To investigate the impact of short-term HS on the remobilization of nonstructural carbohydrates (NSCs) in rice, two cultivars (Huaidao-5 and Wuyunjing-24) were subjected to varying temperature regimes: 32/22/27 °C as the control treatment, alongside 40/30/35 °C and 44/34/39 °C, for durations of 2 and 4 days during the booting, flowering, and combined stages (booting + flowering) within phytotrons across the years 2016 and 2017. The findings revealed that the stem’s NSC concentration increased, while the panicle’s NSCs concentration, the efficiency of NSCs translocation from the stem, and the stem NSC contribution to grain yield exhibited a consistent decline. Additionally, sugar and starch concentrations increased in leaves and stems during late grain filling and maturity stages, while in panicles, the starch concentration decreased and sugar concentration increased. The heat-tolerant cultivar, Wuyunjing-24, exhibited higher panicle NSC accumulation under HS than the heat-sensitive cultivar, Huaidao-5, which had more stem NSC accumulation. The flowering stage was the most vulnerable to HS, followed by the combined and booting stages. Heat degree days (HDDs) were utilized to quantify the effects of HS on NSC accumulation and translocation, revealing that the flowering stage was the most affected. These findings suggest that severe HS makes the stem the primary carbohydrate storage sink, and alleviation under combined HS aids in evaluating NSC accumulation, benefiting breeders in developing heat-tolerant rice varieties.