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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. [ABSTRACT FROM AUTHOR]

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 (Tmean 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, YPPO (only original tillers) declined by 2.9%, 2.5%, and 6.0%, and YPPT (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. [ABSTRACT FROM AUTHOR]

Global climate change has increased the frequency of extreme climate events, and their effects on the nutritional quality, especially on amino acids in rice, have not been quantified. The data from a 3-year low temperature stress (LTS) experiment including two rice varieties (Huaidao 5 and Nanjing 46), seven minimum/maximum temperature levels (one optimal 21/27°C and six LTS levels from 17/23 to 6/12°C), and three LTS durations (3, 6, and 9 days) after flowering, revealed significant interactive effects of LTS at different stages, durations, and temperature levels on the content and accumulation of amino acids. LTS increased rice total amino acid content, while decreasing its accumulation, with higher sensitivities to LTS at the flowering stage than at the grain filling stage. In most treatments, the lysine (the first limiting amino acid) and phenylalanine content were increased under LTS at early and peak flowering stages but decreased at the grain filling stage in both varieties, and only leucine content was increased at all three stages after flowering, while the content of other essential amino acids differed among the two varieties. With an increase of 1°C·d per day in the accumulated cold degree days, the relative content of the essential amino acids was increased by 0.01–0.41%, depending on the rice variety and growth stage. Our results suggest that LTS can improve nutritional quality of amino acids of rice grains in terms of amino acids content, especially at flowering stage. These results provide critical insights for assessing the potential impact of extreme climates on the nutrient quality of rice under future climate change. [ABSTRACT FROM AUTHOR]

Despite global warming, extreme low-temperature stress (LTS) events pose a significant threat to rice production (especially in East Asia) that can significantly impact micronutrient and heavy metal elements in rice. With two billion people worldwide facing micronutrient deficiencies (MNDs) and widespread heavy metal pollution in rice, understanding these impacts is crucial. We conducted detailed extreme LTS experiments with two rice (Oryza sativa L.) cultivars (Huaidao 5 and Nanjing 46) grown under four temperature levels (from 21/27 °C to 6/12 °C) and three LTS durations (three, six, and nine days). We observed significant interaction effects for LTS at different growth stages, durations and temperature levels on the contents and accumulation of mineral elements. The contents of most mineral elements (such Fe, Zn, As, Cu, and Cd) increased significantly under severe LTS at flowering, but decreased under LTS at the grain-filling stage. The accumulations of all mineral elements decreased at the three growth stages under LTS due to decreased grain weight. The contents and accumulation of mineral elements were more sensitive to LTS at the peak flowering stage than at the other two stages. Furthermore, the contents of most mineral elements in Nanjing 46 show larger variation under LTS compared to Huaidao 5. Accumulated cold degree days (ACDD, °C·d) were found to be suitable for quantifying the effects of LTS on the relative contents and accumulations of mineral elements. LTS at the flowering stage will help alleviate MNDs, but may also increase potential health risks from heavy metals. These results provide valuable insights for evaluating future climate change impacts on rice grain quality and potential health risks from heavy metals. [Display omitted] • LTS effects on mineral elements depend on growth stages, LTS durations and levels. • LTS at flowering will alleviate the MNDs, but also increased heavy metals content. • ACDD quantified the LTS effect on content and accumulation of mineral elements well. • LTS effects on mineral elements at early flowering stage was more sensitive than other treatment stages. [ABSTRACT FROM AUTHOR]

Extreme heat-stress events are becoming more frequent under anticipated global warming, which is having devastating effect on grain yield, as well as quality, of rice (Oryza sativa L.). The effects of heat stress at booting stage on grain quality of two japonica varieties, Nanjing41 and Wuyunjing24, were investigated in phytotrons during 2014 and 2015. Rice plants were subjected to four mean temperature regimes 27°C, 31°C, 35°C and 39°C of 2, 4 and 6 days' duration. The results showed that high temperatures of 35°C and 39°C for 4 and 6 days significantly reduced panicle size, seed-setting rate, grain size, chalky grain rate, milling characteristics and amylose content, but increased protein content. Severe heat stress decreased values of peak viscosity and breakdown, and increased pasting temperature. An increase in heat degree-days decreased the percentage of chalky grains exponentially, and decreased amylose content and increased protein content linearly. Sensitivity of grain quality to heat stress in the two varieties differed among quality traits and with heat stress intensity. This study indicates that rice-grain quality had some resistance to mild heat stress, but it could not withstand severe heat stress at booting. Short-term heat stress at booting stage deteriorates most grain-quality traits, posing a potential risk to rice quality. The impacts on grain quality could be well quantified by the combined effects of the intensity and duration of heat stress at booting stage. Short-term heat stress at booting significantly reduced grain size, chalky grain rate, milling quality and amylose content, but increased protein content. Severe heat stress at booting decreased values of peak viscosity and breakdown, and increased pasting temperature of rice. The impacts on rice grain quality could be quantified by the combined effects of the intensity and duration of heat stress at booting stage. [ABSTRACT FROM AUTHOR]

The leaf angle between stem and sheath (SSA) is an important rice morphological trait. The objective of this study was to develop and validate a dynamic SSA model under different nitrogen (N) rates for selected rice cultivars. The time-course data of SSA were collected in three years, and a dynamic SSA model was developed for different main stem leaf ranks under different N rates for two selected rice cultivars. SSA increased with tiller age. The SSA of the same leaf rank increased with increase in N rate. The maximum SSA increased with leaf rank from the first to the third leaf, then decreased from the third to the final leaf. The relationship between the maximum SSA and leaf rank on main stem could be described with a linear piecewise function. The change of SSA with thermal time (TT) was described by a logistic equation. A variety parameter (the maximum SSA of the 3rd leaf on main stem) and a nitrogen factor were introduced to quantify the effect of cultivar and N rate on SSA. The model was validated against data collected from both pot and field experiments. The relative root mean square error (RRMSE) was 11.56% and 14.05%, respectively. The resulting models could be used for virtual rice plant modeling and plant-type design. [ABSTRACT FROM AUTHOR]

Quantitative study of root morphological characteristics of plants is helpful for understanding the relationships between their morphology and function. However, few studies and little detailed and accurate information of root characteristics were reported in fine-rooted plants like rice (Oryza sativa L.). The aims of this study were to quantitatively classify fine lateral roots (FLRs), thick lateral roots (TLRs), and nodal roots (NRs) and analyze their dynamics of mean diameter (MD), lengths and surface area percentage with growth stages in rice plant. Pot experiments were carried out during three years with three rice cultivars, three nitrogen (N) rates and three water regimes. In cultivar experiment, among the three cultivars, root length of ‘Yangdao 6’ was longest, while the MD of its FLR was the smallest, and the mean diameters for TLR and NR were the largest, the surface area percentage (SAP) of TLRs (SAPT) was the highest, indicating that Yangdao 6 has better nitrogen and water uptake ability. High N rate increased the length of different types of roots and increased the MD of lateral roots, decreased the SAP of FLRs (SAPF) and TLRs, but increased the SAP of NRs (SAPN). Moderate decrease of water supply increased root length and diameter, water stress increased the SAPF and SAPT, but decreased SAPN. The quantitative results indicate that rice plant tends to increase lateral roots to get more surface area for nitrogen and water uptake when available assimilates are limiting under nitrogen and water stress environments. [ABSTRACT FROM AUTHOR]

Frequent extreme heat events are the serious threat to rice production, but the historical trend of heat stress associated with phenology shift and its impact on rice yield over a long period are poorly known. Based on the analysis of observed climate and phenology data from 228 stations in South China during 1981-2010, the spatio-temporal variation of post-heading heat stress was investigated among two single-season rice sub-regions in the northern Middle and Lower Reaches of Yangtze River (S-NMLYtz) and Southwest Plateau (S-SWP), and two double-season early rice sub-regions in the southern Middle and Lower Reaches of Yangtze River (DE-SMLYtz) and Southern China (DE-SC). Post-heading heat stress was more severe in DE-SMLYtz, west S-NMLYtz and east S-SWP than elsewhere, because of rice exposure to the hot season during post-heading stage. The spatial variation of post-heading heat stress was greater in single-season rice region than in double-season early rice region due to the greater spatial variation of heading and maturity dates. Post-heading heat stress increased from 1981 to 2010 in most areas, with significant increases in the east of double-season early rice region and west S-SWP. Phenology shift during 1981-2010 mitigated the increasing trends of heat stress in most areas, but not in west S-SWP. Post-heading heat stress played a dominated role in the reduction of rice yield in South China. Grain yield was more sensitive to post-heading heat stress in double-season early rice region than that in single-season rice region. Rice yield decreased by 1.5%, 6.2%, 9.7% and 4.6% in S-NMLYtz, S-SWP, DE-SMLYtz and DE-SC, respectively, because of post-heading heat stress during 1981-2010, although there were some uncertainties. Given the current level and potential increase of post-heading heat stress in South China, the specific adaptation or mitigation strategies are necessary for different sub-regions to stabilize rice production under heat stress. [ABSTRACT FROM AUTHOR]

Abstract: China is one of the most important rice production countries in the world, and maintaining high rice productivity in China is very important for world food security. While previous studies showed that rice production in China has been and will be negatively impacted by global warming, the confounding effects of climatic change, variety improvement and agronomic managements have not been separately investigated. In this paper we combine an analysis of climate and rice growth data with crop modeling to investigate the impact of changes in climate, rice varieties, and agronomic management on rice productivity at four sites (Wuchang, Xinyang, Zhenjiang and Hanyuan) in China. The results showed a significant increase in minimum temperature during all rice growth stages at Wuchang and Zhenjiang, and from heading to maturity at Xinyang, but little change at Hanyuan. Global warming would have led to a reduction in the length of rice growing period and a reduction in grain yield at all study sites, if no varietal changes had occurred. However, the adoption of new rice varieties stabilized growing duration, increased harvest index and grain yield at three of the four sites. In the face of future warming, a planned breeding effort may be needed to offset the negative impact of future climate change. [Copyright &y& Elsevier]

There is unprecedented increase in low-temperature stress (LTS) during post-heading stages in rice as a consequence of the recent climate changes. Quantifying the effect of LTS on yields is key to unraveling the impact of climatic changes on crop production, and therefore developing corresponding mitigation strategies. The present research was conducted to analyze and quantify the effect of post-heading LTS on rice yields as well as yield and grain filling related parameters. A two-year experiment was conducted during rice growing season of 2018 and 2019 using two Japonica cultivars (Huaidao 5 and Nanjing 46) with different low-temperature sensitivities, at four daily minimum/maximum temperature regimes of 21/27 °C (T1), 17/23 °C (T2), 13/19 °C (T3) and 9/15 °C (T4). These temperature treatments were performed for 3 (D1), 6 (D2) or 9 days (D3), at both flowering and grain filling stages. We found LTS for 3 days had no significant effect on grain yield, even when the daily mean temperature was as low as 12 °C. However, LTS of between 6 and 9 days at flowering but not at filling stage significantly reduced grain yield of both cultivars. Comparatively, Huaidao 5 was more cold tolerant than Nanjing 46. LTS at flowering and grain filling stages significantly reduced both maximum and mean grain filling rates. Moreover, LTS prolonged the grain filling duration of both cultivars. Additionally, there was a strong correlation between yield loss and spikelet fertility, spikelet weight at maturity, grain filling duration as well as mean and maximum grain filling rates under post-heading LTS (p < 0.001). Moreover, the effect of post-heading LTS on rice yield can be well quantified by integrating the canopy temperature (CT) based accumulated cold degree days (ACDDCT) with the response surface model. The findings of this research are useful in modeling rice productivity under LTS and for predicting rice productivity under future climates. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION High temperature stress (HTS) has become a serious threat to rice grain quality and few studies have examined the effects of HTS across multiple stages on rice grain quality. In the present study, we conducted 2 years of HTS treatments under three temperature regimes (32/22 °C, 40/30 °C and 44/34 °C) and HTS durations of 2 days and 4 days at three critical stages: booting, flowering, and a combination of booting and flowering. We employed the heat degree days (HDD) metric, which accounts for both the level and duration of HTS, to quantify the relationships between grain quality traits and HTS.The results revealed the diverse effects of HTS on rice grain quality at different stages, durations and temperature levels. HTS significantly (P < 0.05) reduced grain quality, with the highest sensitivities (reduction per 1 °C day−1 increase in HDD) observed at the flowering stage, followed by the combined and booting stages treatments under mild HTS treatment (40/30 °C). However, under extreme HTS treatments (44/34 °C) for 4 days, rice grains subjected to combined HTS treatment experienced complete mortality.Pre‐exposed to HTS at the booting stage within a certain intensity can alleviate the adverse effects of post‐flowering HTS on grain quality. This provides valuable insights for assessing the potential impact of multiple HTS events on the grain quality under future climate warming. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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 (BPPM), 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, BPPM 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 BPPM. However, for biomass, from the first day of high-temperature treatment to maturity (BPPT-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. [ABSTRACT FROM AUTHOR]

Maintaining high double rice productivity in China is very important for ensuring the food security of China. However, the double rice production system is sensitive to changes in both climate and management practices. Previous studies showed that rice production has been negatively impacted by global warming without considering the changes of cultivars and management practices. However, cultivar improvements and the impact of cultivar change must not be ignored in any assessment. In the current study, we combined data analysis with crop modeling to investigate the impacts of changes in climate and cultivars on rice productivity at three different double rice sites (Nanchang, Hengyang, and Gaoyao) in China. The results showed a warming trend at the study sites during 1981–2009, and the temperature increase rates (maximum, average, and minimum temperatures) in the late rice growing season were larger than in the early rice growing season. Global warming has led to a reduction in the length of the rice growth period. Adopting new rice cultivars may partially mitigate the declining trend of the growing duration and grain yield, but it would not completely compensate for the negative impact observed in double rice regions. In general, the changes in cultivars prolonged the growing duration by increasing the basic vegetative phase and the photoperiod formation phase. The main reasons for yield improvement were the increase in the percentage of filled grains for early rice and the increase in grain number per spike for late rice. In the face of future warming, breeding efforts are necessary for producing new cultivars that are resilient to the negative impacts of future climate change on agriculture. [ABSTRACT FROM AUTHOR]

• Current crop models poorly simulate leaf-level photosynthesis under low-temperature stress. • Improved algorithms based on accumulated cold degree days effectively quantify the damage of low-temperature stress on leaf-level photosynthesis. • Improved algorithms quantify the recovery process of leaf-level photosynthesis after low-temperature stress. • Improved algorithms consider sensitivities of different rice cultivars to low-temperature stress. Photosynthesis is crucial for crop growth and yield, yet remains a limitation in enhancing crop production under global climate change. Crop models have been widely used to project the impacts of climate change on crop yields, including extreme temperature events. However, most crop simulation models performed poorly on leaf-level photosynthesis simulation under low-temperature stress (LTS). Here, two rice cultivars, Huaidao 5 and Nangeng 46, were treated under seven LTS intensities (from 27/21 °C to 12/6 °C) and five LTS durations (from 3 to 9 days) during the flowering stage for three years under environment-controlled conditions. The results showed that the observed maximum photosynthetic rate (P max) and initial light-use efficiency (ε) decreased with increasing intensities and durations of LTS, and P max and ε were linearly correlated (R2 = 0.94). Experimental data under different LTS have been tested by four widely used rice models, including RiceGrow, ORYZA2000, RICEPSM, and GEMRICE, indicating that the effects of LTS durations on P max and ε have not been captured well by most existing models. By integrating accumulated cold degree days (ACDD, °C·d) as the LTS index with a cultivar-specific low-temperature threshold parameter (T h), algorithms of temperature factor (FT) and ε were improved, and the effects of LTS on P max and ε were quantified with a double exponential decay function in this research. Compared with the original models, the normalized root mean square error (NRMSE) between observed and simulated photosynthetic rates in the four improved models decreased by about 80 % under LTS treatments, indicating the better performance of the improved models. In addition, the recovery factor of LTS damage to photosynthesis (FLT recover) algorithm was developed to simulate the recovery of the leaf-level photosynthetic rate (P) after LTS treatments. This study could provide an effective quantitative tool for accurately estimating rice photosynthetic production and grain yield under future climate conditions. [ABSTRACT FROM AUTHOR]

Seed-setting rate of rice ( Oryza sativa L.) significantly decreases under high temperatures during the reproductive period largely due to heat-induced spikelet sterility. The effects depend largely on the timing and severity of heat stress, but the variation in the sensitivity of seed-setting rate in response to heat stress at different growth stages is not yet well simulated by most of the present crop models. To investigate the quantitative relationships between seed-setting rates of rice and various exposures of heat stress, we conducted four-year phytotron experiments with four different temperature regimes (the target maximum/minimum temperatures, 32 °C/22 °C, 35 °C/25 °C, 38 °C/28 °C and 41 °C/31 °C in 2011 and 2012; 32 °C/22 °C, 36 °C/26 °C, 40 °C/30 °C and 44 °C/34 °C in 2014 and 2015) with factorial combinations of durations (2, 4 and 6 days in 2014 and 2015; 3, 5 and 7 days in 2011; 3, 6 and 9 days in 2012) and the timings (0, 6 or 12 days after flowering), using three japonica cultivars. The duration and intensity of heat stress were quantified by the heat degree-days (HDD), defined as the temperature sum above a critical temperature value, which varied from 35 to 36 °C, depending on the cultivars. The observed seed-setting rates were well expressed as a logistic function of HDD, but the temperature sensitivity parameter varied with the timing of heat stress and the spikelet positions on the panicle. The variation in timing of flowering was apparent among upper, middle and lower parts of the panicles: 1 and 3-day delay of flowering for the spikelets on the middle and lower parts of the panicles, respectively, compared with upper ones. We therefore developed a simulation model that reflects the changes in the sensitivity of seed-setting rate to HDD to estimate the effects of heat stress with different intensities or durations at any time from flowering onward. The model with the stage-dependent parameters improved substantially the root mean square error (RMSE) and mean bias error (MBE) of seed-setting % from 20.1 and 6.0 to 7.6 and 0.2, respectively, compared to that with the stage-independent parameters. The proposed model needs to be tested under field conditions, but will be an important basis for accurate prediction of seed-setting rates in rice, which is critical for reliable estimates of crop production under climate change. [ABSTRACT FROM AUTHOR]

Extreme heat stress occurred frequently with increasing global warming, and significantly reduced crop yield. Experimental and modelling studies for grain yield formation under heat stress were widely carried out, but carbohydrate and nitrogen re-distribution caused by unbalanced sink-source relationships have rarely been noticed. The multi-year experimental datasets involving different heat stress intensities, durations, and rice varieties showed that rice stem was re-activated as a sink organ during grain filling stage after short-term extreme heat stress at flowering, where a large amount of carbohydrate and nitrogen accumulated. The stems may become alternative harvest organs under climate change, whereas needs accurate assessments for adaptation strategy. We further improved the simulation of biomass and nitrogen accumulation in different rice organs according to the re-evaluated sink-source relationship under heat stress, based on RiceGrow model. The nitrogen filling process in stems after the termination of grain filling was quantified, and the delay of leaf senescence was also simulated by accounting for the leaf nitrogen distribution within the canopy under heat stress. The improved model explained the cause and effect of unusual carbohydrate and nitrogen accumulation under heat stress in rice, and can be a useful tool for adaptation strategy under climate change. • Carbohydrate and nitrogen were accumulated in stems after extreme heat stress at flowering. • Re-evaluated sink-source relationship were used to simulate biomass and nitrogen partitioning. • Leaf senescence was modelled by accounting for leaf nitrogen distribution within canopy. • The improved model simulated carbohydrate and nitrogen dynamics well under heat stress. [ABSTRACT FROM AUTHOR]

Heat stress significantly accelerates senescence process during reproductive phase in rice, but the effects of heat stress are not yet well simulated by most of the existing crop models. Three-year experiments under different temperature levels and temperature durations at anthesis and 12 days after anthesis were carried out in phytotron using two japonica cultivars. Significant positive correlations were observed between the shortened grain growing days from anthesis to maturity (GD AM ) and heat degree-days (HDD). The impact of post-anthesis heat stress on rice phenology was quantified by adding thermal effectiveness of heat stress to the original RiceGrow model. Performance of the improved model was tested with phenological data from different cultivars under post-anthesis heat stress of phytotron environments and field conditions. Validation results showed that root mean square error (RMSE), mean bias error (MBE) and variance of the distribution of differences ( S d 2 ) for the prediction of GD AM , decreased from 4.60 d, 2.65 d and 7.80 in the original model to 1.58 d, −0.16 d and 2.40 in the improved model, respectively, under post-anthesis heat stress conditions. The determination coefficient ( R 2 ) and index of agreement (IA) between simulated and observed GD AM , increased from 68.5% and 0.71 in the original model to 93.5% and 0.92 in the improved model under post-anthesis heat stress conditions, respectively. Overall, the improved model gave better predictions of GD AM in different rice cultivars under different post-anthesis heat stress environments. Our study highlights the necessity of accurately simulating the heat stress effects on phenological processes in rice to forecast crop production for ensuring food security under climate change reliably. [ABSTRACT FROM AUTHOR]

Highlights: [•] A detailed 3D panicle morphological model was developed. [•] Dynamic models of panicle and branch curves, and panicle color were built. [•] Based on our models, the dynamic visualization of 3D rice panicle was realized. [ABSTRACT FROM AUTHOR]

• A multi-crop model ensemble approach was used to assess the impacts of 1.5 °C and 2.0 °C global warming on rice production. • Total production will derease by 5.3% and 11.4% without CO 2 effect under 1.5 °C and 2.0 °C scenarios. • Elevated CO 2 could offset the negative impacts of increasing temperature mostly. • Global warming has a positive effect on rice yield under elevated CO 2 in northeast China. The primary goal of the 2015 Paris Climate Agreement is to limit future global warming to less than 2.0 °C above pre-industrial levels. Thus, understanding the impacts of relatively low warming level on rice production is essential to future food security of China. Here, with the latest global warming scenarios from the Half a degree Additional warming, Projections, Prognosis and Impacts (HAPPI) project, we assess the impacts of the two HAPPI scenarios (1.5 °C and 2.0 °C warming above pre-industrial levels) on rice production for two major rice-cropping systems, including single-season rice and double-season rice (early- and late-season rice). A multi-model ensemble approach (three crop models and four climate models) was used to predict the changes of rice production across the main rice-growing regions of China under 1.5 °C and 2.0 °C warming scenarios. Results show that increases in mean rice growing season temperature (GST) under 1.5 °C and 2.0 °C warming scenarios are highest in central China. Likewise, the increase in GST during the reproductive growth phase (GST-r) is greater than that during the vegetative growth phase (GST-v). The whole rice-growing season duration (GSD-w) is shortened by about 3–15 and 4.5–18 days under 1.5 °C and 2.0 °C warming scenarios, respectively. Most of the shortening in GSD-w occurs due to a shortening of the vegetative growth phase (GSD-v). Using a stepwise multiple regression procedure, we find that the yield changes of single-season rice and late-season rice are significantly negatively correlated with both GST-r and GSD-v. When examining early-season rice, yield changes are significantly negatively correlated with both GST-v and GSD-r. Under 1.5 °C and 2.0 °C warming scenarios without carbon dioxide (CO 2) fertilization effects, the impact of warming has a negative effect across the main rice-growing regions of China. The reduction is greater in the southern area than that in the northern section of the study regions. However, climatic warming has a positive effect on rice yield in low thermal regions of northeast China with CO 2 fertilization effects. In other regions, CO 2 fertilization will not offset the negative impacts on rice production due to climatic warming. Our results will aid in making the future adaptation strategies to moderate the negative impacts of climate warming on regional rice production across China. [ABSTRACT FROM AUTHOR]