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Physiological and molecular attributes contribute to high night temperature tolerance in cereals
Abstract
Asymmetric warming resulting in a faster increase in night compared to day temperatures affects crop yields negatively. Physiological characterization and agronomic findings have been complemented more recently by molecular biology approaches including transcriptomic, proteomic, metabolomic and lipidomic investigations in crops exposed to high night temperature (HNT) conditions. Nevertheless, the understanding of the underlying mechanisms causing yield decline under HNT is still limited. The discovery of significant differences between HNT‐tolerant and HNT‐sensitive cultivars is one of the main research directions to secure continuous food supply under the challenge of increasing climate change. With this review, we provide a summary of current knowledge on the physiological and molecular basis of contrasting HNT tolerance in rice and wheat cultivars. Requirements for HNT tolerance and the special adaptation strategies of the HNT‐tolerant rice cultivar Nagina‐22 (N22) are discussed. Putative metabolite markers for HNT tolerance useful for marker‐assisted breeding are suggested, together with future research directions aimed at improving food security under HNT conditions.
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... In spite of warmer winters, however, the change in the average date of the last spring frost is not consistent across the region. 349 Higher temperatures, particularly overnight temperatures, have reduced crop yields, 350 and these impacts are projected to worsen with additional global warming (Figure 22.19; Ch. 11). They have also led to an increase in the occurrence of drought in the region (Figure 22.18). ...
... Evidence of trends in temperature, precipitation, and growing season are well documented in sources such as the NOAA National Centers for Environmental Information's Climate at a Glance Tool and in the scientific literature. 346,350 This literature base is extensive and covers individual states, the Southeast region, the United States, and the globe. Earlier concerns about temperature trends from satellite observations, which did not match surface-based observations, have largely been resolved by improved calibration of satellite measurements. ...
... 351,352 The impacts of climate variability and change on agricultural production have been well documented in the scientific literature in agricultural journals in recent years. 350,356 More work is ongoing as better methods for collecting in-field measurements are used to fine-tune the relationships between plant physiology and climate variables. ...
The Global Change Research Act of 1990 mandates that the US Global Change Research Program (USGCRP) deliver a report to Congress and the President not less frequently than every four years that “integrates, evaluates, and interprets the findings of the Program and discusses the scientific uncertainties associated with such findings; analyzes the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity; and analyzes current trends in global change, both human-induced and natural, and projects major trends for the subsequent 25 to 100 years.”
The Fifth National Climate Assessment (NCA5) fulfills that mandate by delivery of this Assessment and provides the scientific foundation to support informed decision-making across the United States.
The report cited in my research gate site represents the chapter that is focused on the Southeastern US.
... Additionally, there is a current renewed interest in understanding the effects of high night temperature (HNT) on cereals [206][207][208]. Asymmetric warming causing a rapid increase in nocturnal versus diurnal temperatures has been observed and is predicted to continue, posing significant challenges to cereal crop productivity [207,208]. ...
... Additionally, there is a current renewed interest in understanding the effects of high night temperature (HNT) on cereals [206][207][208]. Asymmetric warming causing a rapid increase in nocturnal versus diurnal temperatures has been observed and is predicted to continue, posing significant challenges to cereal crop productivity [207,208]. Yet, our knowledge of the impacts of HNT, and tolerance mechanisms in cereals is still limited [207]. Therefore, this topic warrants further research. ...
... Asymmetric warming causing a rapid increase in nocturnal versus diurnal temperatures has been observed and is predicted to continue, posing significant challenges to cereal crop productivity [207,208]. Yet, our knowledge of the impacts of HNT, and tolerance mechanisms in cereals is still limited [207]. Therefore, this topic warrants further research. ...
Reproductive-stage heat stress (RSHS) poses a major constraint to cereal crop production by damaging main plant reproductive structures and hampering reproductive processes, including pollen and stigma viability, pollination, fertilization, grain setting and grain filling. Despite this well-recognized fact, research on crop heat stress (HS) is relatively recent compared to other abiotic stresses, such as drought and salinity, and in particular, RSHS studies in cereals are considerably few in comparison with seedling-stage and vegetative-stage-centered studies. Meanwhile, climate change-exacerbated HS, independently or synergistically with drought, will have huge implications on crop performance and future global food security. Fortunately, due to their sedentary nature, crop plants have evolved complex and diverse transient and long-term mechanisms to perceive, transduce, respond and adapt to HS at the molecular, cell, physiological and whole plant levels. Therefore, uncovering the molecular and physiological mechanisms governing plant response and tolerance to RSHS facilitates the designing of effective strategies to improve HS tolerance in cereal crops. In this review, we update our understanding of several aspects of RSHS in cereals, particularly impacts on physiological processes and yield; HS signal perception and transduction; and transcriptional regulation by heat shock factors and heat stress-responsive genes. We also discuss the epigenetic, post-translational modification and HS memory mechanisms modulating plant HS tolerance. Moreover, we offer a critical set of strategies (encompassing genomics and plant breeding, transgenesis, omics and agronomy) that could accelerate the development of RSHS-resilient cereal crop cultivars. We underline that a judicious combination of all of these strategies offers the best foot forward in RSHS tolerance improvement in cereals. Further, we highlight critical shortcomings to RSHS tolerance investigations in cereals and propositions for their circumvention, as well as some knowledge gaps, which should guide future research priorities. Overall, our review furthers our understanding of HS tolerance in plants and supports the rational designing of RSHS-tolerant cereal crop cultivars for the warming climate.
... Of particular note, predictions indicate that by the year 2030, roughly 16% of the global area for rice cultivation may be exposed to over 5 d of heat stress during the reproductive phase (Gourdji et al, 2013). The looming threat of high temperature stress (HTS) to rice production has attracted considerable attention Hu et al, 2021;Zhen et al, 2020b;Schaarschmidt et al, 2021). ...
... The reproductive phase of rice is highly vulnerable to heat stress (Jagadish et al, 2007;Shi et al, 2017;Wu et al, 2017). Numerous investigations have established that temperatures surpassing the critical thresholds of 33 ºC or 35 ºC have deleterious effects on rice yield by impeding spikelet fertility, shortening grain filling duration, diminishing grain weight, and compromising grain quality Zhen et al, 2020a, b;Schaarschmidt et al, 2021;Chen et al, 2021;Wu et al, 2023). At the flowering or grain-filling stages, even short periods of heat stress (> 33 ºC) can negatively impact rice yield (Shi P H et al, 2016;Sun et al, 2018). ...
Due to climate change, extreme heat stress events have become more frequent, adversely affecting rice yield and grain quality. Accumulation and translocation of dry matter and nitrogen
substances are essential for rice yield and grain quality. To assess the impact of high temperature stress (HTS) at the early panicle initiation (EPI) stage on the accumulation, transportation and distribution of dry matter and nitrogen substances in organs, as well as its effects on rice yield and grain quality, pot experiments with indica rice Yangdao 6 (YD6) and japonica rice Jinxiangyu 1 (JXY1) were conducted under normal temperature (NT, 32 ºC / 26 ºC) and HTS (38 ºC / 29 ºC). The results indicated that exposure
to HTS at the EPI stage significantly decreased rice yield by reducing spikelet number per panicle, grain filling rate and grain weight. In addition, it improved the nutritional quality of rice grains by increasing protein and amylose contents. The reduction in nitrogen and dry matter accumulation accounted for the changes in spikelet number per panicle, grain filling rate and grain size. Under HTS, the decrease in nitrogen accumulation accompanied by the reduction in dry matter may due to the down-regulation of leaf net photosynthesis and senescence as evidenced by the decrease in nitrogen content. Furthermore, the decrease in sink size limited the translocation of dry matter and nitrogen substances to grains, which was closely related to the reduction in grain weight and deterioration of grain quality. These findings contribute significantly to our understanding of the mechanisms of HTS on grain yield and quality formation from the perspective of dry matter and nitrogen accumulation and translocation. Further efforts are needed to improve the adaptation of rice varieties to climate change in near future.
... Of particular note, predictions indicate that by the year 2030, roughly 16% of the global area for rice cultivation may be exposed to over 5 d of heat stress during the reproductive phase (Gourdji et al, 2013). The looming threat of high temperature stress (HTS) to rice production has attracted considerable attention Hu et al, 2021;Zhen et al, 2020b;Schaarschmidt et al, 2021). ...
... The reproductive phase of rice is highly vulnerable to heat stress (Jagadish et al, 2007;Shi et al, 2017;Wu et al, 2017). Numerous investigations have established that temperatures surpassing the critical thresholds of 33 º C or 35 º C have deleterious effects on rice yield by impeding spikelet fertility, shortening grain filling duration, diminishing grain weight, and compromising grain quality Zhen et al, 2020a, b;Schaarschmidt et al, 2021;Chen et al, 2021;Wu et al, 2023). At the flowering or grain-filling stages, even short periods of heat stress (> 33 º C) can negatively impact rice yield (Shi P H et al, 2016;Sun et al, 2018). ...
Due to climate change, extreme heat stress events have become more frequent, adversely affecting rice yield and grain quality. Accumulation and translocation of dry matter and nitrogen substances are essential for rice yield and grain quality. To assess the impact of high temperature stress (HTS) at the early panicle initiation (EPI) stage on the accumulation, transportation and distribution of dry matter and nitrogen substances in organs, as well as its effects on rice yield and grain quality, pot experiments with indica rice Yangdao 6 (YD6) and japonica rice Jinxiangyu 1 (JXY1) were conducted under normal temperature (NT, 32 º C / 26 º C) and HTS (38 º C / 29 º C). The results indicated that exposure to HTS at the EPI stage significantly decreased rice yield by reducing spikelet number per panicle, grain filling rate and grain weight. In addition, it improved the nutritional quality of rice grains by increasing protein and amylose contents. The reduction in nitrogen and dry matter accumulation accounted for the changes in spikelet number per panicle, grain filling rate and grain size. Under HTS, the decrease in nitrogen accumulation accompanied by the reduction in dry matter may due to the down-regulation of leaf net photosynthesis and senescence as evidenced by the decrease in nitrogen content. Furthermore, the decrease in sink size limited the translocation of dry matter and nitrogen substances to grains, which was closely related to the reduction in grain weight and deterioration of grain quality. These findings contribute significantly to our understanding of the mechanisms of HTS on grain yield and quality formation from the perspective of dry matter and nitrogen accumulation and translocation. Further efforts are needed to improve the adaptation of rice varieties to climate change in near future.
... Both warming and CFE alter grain filling in rice; thus, post-heading heat stress ( Figure 3) and the early milky stage (Figure 2) are concerning themes. Given that the duration of grain filling, post-flowering senescence, changes in the starch and protein content of rice grains, starch metabolism enzymes, and chalk formation in rice grains are sensitive to warming [31,88,89], field-observed experiments and model simulation studies are required to identify and breed tolerant cultivars. ...
... Both the quantity and quality of rice grains are determined by the process of grain filling or grain growth at the point of the rice plant, which is determined by both genetic and environmental factors. Thus, ICCRG studies involve multiple areas, including plant physiology, agronomy, ecology, environmental sciences, socio-economic sciences, etc. [88][89][90][91][92]. There is a trend in the studies on ICCRG shifting toward molecular biology for breeding tolerant cultivars, as shown by "metabolomics" in Figure 2 and "quantitative trait loci" and "gene expression" in Figure 4. ...
More than half of the people on Earth get their calories, proteins, and minerals from rice grains. Staple increases in the quantity and quality of rice grains are key to ending hunger and malnutrition. Rice production, however, is vulnerable to climate change, and the climate on Earth is becoming more fluctuating with the atmospheric change induced by human activities. As a result, the impacts of climate change on rice grain (ICCRG) have sparked widespread concern. In order to reveal the development and the trend in the study on the ICCRG, a bibliometric analysis was conducted. The results showed that both the model simulations and the field experiment-based observations, as reflected by APSIM (the Agricultural Production Systems sIMulator) and free-air carbon dioxide (CO2) enrichment, are of concern to researchers worldwide, especially in China, India, the United States, and Japan. Different types of warming include short-term, nighttime, soil and water, and canopy, and their interactions with other climate factors, such as CO2, or agronomic factors, such as nitrogen level, are also of concern to researchers. Spatiotemporal variations in changing weather and regional adaptations from developed and developing countries are challenging the evaluation of ICCRG from an economic perspective. In order to improve the efficacy of breeding adaptable cultivars and developing agronomic management, interdisciplinary studies integrating molecular biology, plant physiology, agronomy, food chemistry, ecology, and socioeconomics are needed.
... A large genetic diversity exists in crop plants, with different level of sensitivity observed in response to heat stress, but exploiting higher levels of heat tolerance for crop improvement has been a challenge due to limitations related to phenotyping large populations . Using metabolomics and transcriptomics approaches, Schaarschmidt, Lawas, Kopka, Jagadish, and Zuther (2021) show the relevance of deriving molecular markers to enhance our ability to capture large genetic diversity for heat stress responses. how day and night temperatures have a differential impact on the physiological responses in crops, including rice and wheat. ...
... Schaarschmidt et al. (2021) reveal underlying metabolites and transcripts that differentiate heat-tolerant rice and wheat from susceptible genotypes, indicating the possibility of developing molecular markers to complement ongoing efforts to breed crops with increased heat tolerance.2 | THE IMPORTANCE OF INCREASING NIGHT TEMPERATURESGlobal mean temperature increase hides interesting patterns in temperature change that can affect plant heat responses, such as the greater increase in night-time warming compared to daytime temperature increases (K. ...
... The levels of both reducing sugars (fructose, glucose, maltose) and non-reducing sugars (sucrose and raffinose), along with starch content in the flag leaf, are known to correlate with photosynthetic rates (Schaarschmidt et al., 2021). Nagina 22 exhibited the largest pool of soluble sugars and starch at the end of the day, suggesting higher photosynthetic activity (Sharma et al., 2024). ...
High night temperature (HNT) stress disrupts key physiological processes like respiration, assimilate partitioning, and grain filling, challenging crop production. While the impact of HNT on grain growth and yield is known, the role of sink strength and starch biosynthesis in inferior or superior spikelets, as well as the effects of temporal variations on assimilate distribution, remain underexplored. We hypothesized that a tolerant genotype reallocates sugars to inferior spikelets under HNT stress by enhancing sink strength and starch biosynthesis, with the
second half of the night playing a critical role in these processes. Two rice genotypes, Nagina 22 (HNT-tolerant) and Vandana (HNT-sensitive), were subjected to HNT (4 °C above the control) from flowering to physiological maturity. Assimilate movement and sink enzyme activity were investigated during peak grain-filling. Results revealed differential 14C partitioning to starch synthesis in spikelets, with superior spikelets maintaining higher synthesis rates under HNT. Under HNT, Vandana showed reduced sucrose synthase and ADP-glucose pyrophosphorylase (AGPase) activities (up to 63 % in inferior spikelets), while Nagina 22 exhibited increased sucrose synthase (up to 2.7-fold) and AGPase (up to 31 %) activities in inferior spikelets. Under HNT, Vandana showed reduced starch and sugar levels, while Nagina 22 maintained or increased starch content and exhibited varied sugar responses. Overall, our results confirm that Nagina 22 reallocates sugars to inferior spikelets under HNT stress, driven by enhanced sink strength and starch biosynthesis in the second half of the night. This highlights a novel dimension for developing rice genotypes with improved resilience to HNT, ensuring stable yield under
changing climate.
... Furthermore, as global temperatures continue to rise, there is also an intensifying asymmetry in temperature variation between day and night, specifically manifested in the fact that the increase in the minimum nighttime temperature is three times that of the corresponding maximum daytime temperature [10]. Elevated nighttime temperatures (HNTs) can increase rice respiration, cause oxidative damage, and lead to decreased rice yields [11,12]. Research indicates that an increase in nighttime temperature by 1 • C will lead to a 10% decrease in rice yield [13]. ...
As one of the world’s principal food crops, rice sustains over half of the global population. With global climate change intensifying, the frequency of extreme high temperatures is increasing, posing significant threats to the growth and development, yield, and quality of rice, thereby jeopardizing global food security. This study reviews the impacts of high temperatures on rice at different developmental stages and summarizes previous research on heat tolerance cultivation techniques for rice. Currently, to enhance heat tolerance in rice, the following strategies were primarily adopted: (1) the exploration of heat-tolerant genetic resources and breeding of heat-tolerant varieties; (2) cooling through canopy temperature management via enhanced transpiration regulated by water management; (3) the scientific application of fertilizers to promote the accumulation of assimilates in rice; (4) the application of exogenous regulators to bolster the antioxidant capacity of rice. The implementation of these strategies not only helps to ensure rice yield and quality but also provides robust support for addressing the challenges that global warming poses to agricultural production.
... The increase in nighttime temperature is influenced by various factors such as the increase in cloud cover, desertification, land use changes, changes in the particulate matter (PM) concentrations, evaporation, and changes in the planetary boundary layer (PBL) (Schaarschmidt et al. 2021). ...
This study aims to provide a climatological view of cold spots and a spatiotemporal analysis of minimum land surface temperature (LST) in Iran. We used daily Aqua/MODIS LST product in 1-km resolution (MYD11A1 version 6.1) for 19 years (2003–2021). The findings indicate that Iran’s coldest spots are located in a narrow corridor in the middle part of the Alborz Mountains called the “Iran’s Cold Pole (ICP).” From May to November, a tri-modal distribution of absolute minimum LST (AMLST) exists at ICP. Mount Damavand and Varkash, with − 14.30 °C and − 49.18 °C, set the country’s lowest long-term minimum LST (LTMLST) and AMLST records. The results indicate that the geographical distribution of Iran’s cold spots (ICS) follows the high mountains with an altitude of more than 3500 m throughout the year. However, the AMLSTs are mainly concentrated in northwestern Iran and do not necessarily follow the high mountains. The results reveal that while cold spots are concentrated in the ICP in summer, they are geographically dispersed in winter, with the most dispersion in December. According to the results, the most prolonged cold period and the lowest LSTs occur every year from 38° N to 39° N in Iran. The trend shows that almost all the years after 2012 experienced a positive anomaly in the nighttime LST. Examining the interannual variations of the monthly AMLSTs indicates that very low LSTs and high negative anomalies have decreased during the cold period in recent years.
... Even if, in the present study, the intensity of temperature was as high as 38˚C, HS1 and HS12 treatments were probably not long enough to significantly impair the pericarp growth through cell enlargement. In contrast, in Herrera and Calderini (2020) [43], higher temperatures were applied on a longer duration (from anthesis to 16 DAA) and during night, as night temperature has been shown to affect more negatively cell enlargement than similar day temperature [75][76][77]. ...
Post-anthesis heat shocks, which are expected to increase in frequency under climate change, may affect wheat grain development and lead to significant decreases in grain yield. Grain development occurs in three phases, the lag-phase, the filling-phase, and maturation. The growth of the three main compartments of the grain (outer layers (OLs), endosperm, embryo) is staggered, so that heat shocks affect time- and tissue-specific growth processes differentially depending on their timing. We hypothesized that heat shocks during the lag-phase may reduce final grain size, resulting from a reduction in endosperm cell number and/or a restricted OLs growth. Plants were heated for four consecutive days during the lag-phase or the filling-phase or both phases (lag- and filling-). Heat shocks consisted in four hours a day at 38°C and 21°C for the rest of the day. Controlled plants were maintained at 21/14°C (day/night). For each temperature treatment, kinetics of whole grain and compartment masses and dimensions were measured as well as the endosperm cell number. An early heat shock reduced endosperm cell proliferation. However, the growth patterns neither of endosperm nor of OLs were modified compared to controls, resulting in no differences in final grain size. Furthermore, compared to controls, a single heat shock during the filling-phase reduced both the duration and rate of dry mass accumulation into grains, whereas two consecutive shocks reduced the duration but enhanced the rate of dry mass of accumulation, even when endosperm cell number was reduced. The mean endosperm cell size was shown to be larger after early heat shocks. All together, these results suggest a compensatory mechanism exists to regulate endosperm cell size and number. This process might be a new mechanistic target for molecular studies and would improve our understanding of post-anthesis wheat tolerance to heat-shocks.
... A significant challenge is screening a large number of cultivars to identify heat-tolerant cultivars and thermotolerance traits (Schaarschmidt et al., 2021). The current study was conducted at unprecedented locational and intraspecific scales, relying on a large quantity of measurement data. ...
Extreme temperature, especially heat stress, is increasingly limiting wheat production, resulting in a large yield loss worldwide. Identifying the cultivars, traits and molecular mechanisms conferring extreme high temperature tolerance is essential for comprehending crop resilience to extreme climates and breeding climate-resilient cultivars. Here, we identified 23 extreme high temperature-tolerant cultivars (11.0%) out of 209 wheat cultivars based on mass field experiments. In an extreme high temperature year, wheat grain yield was significantly reduced by 27.1% among all the genotypes. We found that radiation use efficiency, plant height, thousand-grain weight, flag leaf width, accumulated thermal time to flowering, net photosynthetic rate and SPAD at flowering and grain filling rate could be the traits associated with extreme high temperature tolerance. These traits were indicative of yield in two years differing in temperature, exhibiting a high heritability. Additionally, 203 loci associated with these traits were identified. The results indicated that the interval 755.97–767.82 Mb on chromosome
2 A was linked to flag leaf area, grain yield, accumulated thermal time to flowering and maturity, leaf dry weight at flowering and spike dry weight at flowering, resulting in a cumulative genetic effect on yield. Our findings identify wheat cultivars, traits and associated loci for extreme high temperature tolerance selection,
facilitating marker-assisted breeding of cultivars under a changing climate.
... Several questions arise from this work, confirming that high temperature response results from a complex of physiological, cellular and molecular processes, as previously proposed (Jacott and Boden, 2020;Schaarschmidt et al., 2021). Though, several pieces are missing to compose the intricate puzzle of plant response to this abiotic stress Khan et al., 2021). ...
... Several questions arise from this work, confirming that high temperature response results from a complex of physiological, cellular and molecular processes, as previously proposed (Jacott and Boden, 2020;Schaarschmidt et al., 2021). Though, several pieces are missing to compose the intricate puzzle of plant response to this abiotic stress Khan et al., 2021). ...
High temperature (HT) events have negative impact on wheat grains yield and quality. Transcriptome profiles of wheat developing grains of commercial genotypes (Antequera and Bancal) and landraces (Ardito and Magueija) submitted to heatwave-like treatments during grain filling were evaluated. Landraces showed significantly more differentially expressed genes (DEGs) and presented more similar responses than commercial genotypes. DEGs were more associated with transcription and RNA and protein synthesis in Antequera and with metabolism alterations in Bancal and landraces. Landraces upregulated genes encoding proteins already described as HT responsive, like heat shock proteins and cupins. Apart from the genes encoding HSP, two other genes were upregulated in all genotypes, one encoding for Adenylate kinase, essential for the cellular homeostasis, and the other for ferritin, recently related with increased tolerance to several abiotic stress in Arabidopsis. Moreover, a NAC transcription factor involved in plant development, known to be a negative regulator of starch synthesis and grain yield, was found to be upregulated in both commercial varieties and downregulated in Magueija landrace. The detected diversity of molecular processes involved in heat response of commercial and traditional genotypes contribute to understand the importance of genetic diversity and relevant pathways to cope with these extreme events.
... Our analyses showed that rice phenology responded differently to T min , T max and T mean , and T min affected more significantly the GPs for all the three rice types, which was well supported by chambers and field-based studies in cereals across major cropping regions of the world (Peng et al 2004, Impa et al 2021, Schaarschmidt et al 2021, Sakai et al 2022. The stronger negative effects of T min may mostly result from its greater increasing rate (supplementary figure S3). ...
Climate warming has substantially shifted plant phenology, which alters the length of growing season and consequently affects plant productivity. Recent studies showed a stalled or reversed impact of climate change on vegetation phenology since 1998, as well as an asymmetric warming effect. However, how field crop phenology responded to the recent climate warming and the asymmetric warming remains unknown. In addition, the relative roles of climate change, sowing date and cultivars shifts in the spatiotemporal changes of crop phenology at different regions need to be better understood. Here, using the latest 9,393 phenological records at 249 agro-meteorological stations across China over 1981-2018, we critically investigated the spatiotemporal dynamics of rice phenology and disentangled the effects of different drivers by exploiting the physiological relationship between crop phenology and thermal accumulation. The results showed that length of growing period (GP) increased by 3.24 ± 0.15 days/decade for single rice, 1.90 ± 0.22 days/decade for early rice and 0.47 ± 0.14 days/decade for late rice. Although climate warming during rice GP did not slow down, the trends in rice GP and the correlations between GP and temperature decreased generally from 1981-1999 to 2000-2018. The weakened phenological response to climate change was mainly caused by agronomic managements, especially cultivar shifts. Climate warming shortened GP by 0.84 ± 1.80, 1.23 ± 0.77, and 1.29 ± 1.24 days/decade for single rice, early rice and late rice, respectively. However, cultivar shifts prolonged it respectively by 3.28 ± 3.68, 2.15 ± 2.38, and 2.31 ± 3.36 days/decade, totally offsetting the negative effects of climate warming. Rice responded to daytime and night-time warming differently with night-time temperature affecting GPs more. Our study provided new insights that rice phenology responded to night-time warming more than daytime warming across China however the response to climate warming weakened, and cultivar shifts outweighed climate change in affecting rice phenology.
... A new paradigm in the form of metabolomics has emerged as a potential approach to establish signature metabolites as markers associated with agronomically important traits (Schaarschmidt et al., 2021). Metabolite levels are a quantitative trait and hence in QTL mapping and GWAS they are considered as quantitative phenotypic trait. ...
Conventional breeding techniques for crop improvement have reached their full potential, and hence, alternative routes are required to ensure a sustained genetic gain in lentils. Although high-throughput omics technologies have been effectively employed in major crops, less-studied crops such as lentils have primarily relied on conventional breeding. Application of genomics and transcriptomics in lentils has resulted in linkage maps and identification of QTLs and candidate genes related to agronomically relevant traits and biotic and abiotic stress tolerance. Next-generation sequencing (NGS) complemented with high-throughput phenotyping (HTP) technologies is shown to provide new opportunities to identify genomic regions and marker-trait associations to increase lentil breeding efficiency. Recent introduction of image-based phenotyping has facilitated to discern lentil responses undergoing biotic and abiotic stresses. In lentil, proteomics has been performed using conventional methods such as 2-D gel electrophoresis, leading to the identification of seed-specific proteome. Metabolomic studies have led to identifying key metabolites that help differentiate genotypic responses to drought and salinity stresses. Independent analysis of differentially expressed genes from publicly available transcriptomic studies in lentils identified 329 common transcripts between heat and biotic stresses. Similarly, 19 metabolites were common across legumes, while 31 were common in genotypes exposed to drought and salinity stress. These common but differentially expressed genes/proteins/metabolites provide the starting point for developing high-yielding multi-stress-tolerant lentils. Finally, the review summarizes the current findings from omic studies in lentils and provides directions for integrating these findings into a systems approach to increase lentil productivity and enhance resilience to biotic and abiotic stresses under changing climate.
... Conversely, it is now established that high night-time temperatures, which increase disproportionately to daytime temperatures, can be hugely restrictive to yield especially during grain-filling periods and minimum temperatures correlate well with yield losses. Reductions in yield for cereals have been reported as between 1% and 9% for every 1°C increase in nocturnal temperature (for review see Schaarschmidt et al., 2021). Although there is still a lot to be understood about nocturnal heat stress, recent work shows clearly that enhanced respiration can divert photosynthates away from reproductive sinks and towards maintenance respiration. ...
Plant scientists and farmers are facing major challenges in providing food and nutritional security for a growing population, while preserving natural resources and biodiversity. Moreover, this should be done while adapting agriculture to climate change and by reducing its carbon footprint. To address these challenges, there is an urgent need to breed crops that are more resilient to suboptimal environments. Huge progress has recently been made in understanding the physiological, genetic and molecular bases of plant nutrition and environmental responses, paving the way towards a more sustainable agriculture. In this review, we present an overview of these progresses and strategies that could be developed to increase plant nutrient use efficiency and tolerance to abiotic stresses. As illustrated by many examples, they already led to promising achievements and crop improvements. Here, we focus on nitrogen and phosphate uptake and use efficiency and on adaptation to drought, salinity and heat stress. These examples first show the necessity of deepening our physiological and molecular understanding of plant environmental responses. In particular, more attention should be paid to investigate stress combinations and stress recovery and acclimation that have been largely neglected to date. It will be necessary to extend these approaches from model plants to crops, to unravel the relevant molecular targets of biotechnological or genetic strategies directly in these species. Similarly, sustained efforts should be done for further exploring the genetic resources available in these species, as well as in wild species adapted to unfavourable environments. Finally, technological developments will be required to breed crops that are more resilient and efficient. This especially relates to the development of multiscale phenotyping under field conditions and a wide range of environments, and use of modelling and big data management to handle the huge amount of information provided by the new molecular, genetic and phenotyping techniques. In this review we propose prospects to improve crop resilience and sustainability of crop production. We identified major challenges (blue) for future crop production and propose opportunities (green) to address them with the aim to prepare a roadmap for the development of improved crops in the frame of the CropBooster‐P project.
... Follow-up studies investigated metabolic and transcriptomic changes in these rice cultivars under HNT stress and differentiated molecular processes between members of the HNT sensitivity groups [21,22]. Despite the growing and recently reviewed knowledge of natural variation in HNT stress at the molecular level [23], little is known about the detailed HNT response of leaf segments and the development of leaf senescence under HNT stress, particularly in sensitive cultivars. Leaf senescence is a regulated process in plants which leads to the death of cells, tissues or the whole organ. ...
High night temperatures (HNT) affect rice yield in the field and induce chlorosis symptoms in leaves in controlled chamber experiments. However, little is known about molecular changes in leaf segments under these conditions. Transcript and metabolite profiling were performed for leaf segments of six rice cultivars with different HNT sensitivity. The metabolite profile of the sheath revealed a lower metabolite abundance compared to segments of the leaf blade. Furthermore, pre-adaptation to stress under control conditions was detected in the sheath, whereas this segment was only slightly affected by HNT. No unique significant transcriptomic changes were observed in the leaf base, including the basal growth zone at HNT conditions. Instead, selected metabolites showed correlations with HNT sensitivity in the base. The middle part and the tip were most highly affected by HNT in sensitive cultivars on the transcriptomic level with higher expression of jasmonic acid signaling related genes, genes encoding enzymes involved in flavonoid metabolism and a gene encoding galactinol synthase. In addition, gene expression of expansins known to improve stress tolerance increased in tolerant and sensitive cultivars. The investigation of the different leaf segments indicated highly segment specific responses to HNT. Molecular key players for HNT sensitivity were identified.
How much respiration occurs within crop plants, and if their respiration was 'improved,' would growth and yield increase?
Lentil (Lens culinaris Medik.) is a significant cool-season legume crop known for its high nutritional value, often referred to as the ‘poor man’s meat.’ The effects of global climate change have had a notable impact on lentil area and production, primarily due to the introduction of this crop into new niches as well as the increased incidence of diseases and pests affecting this crop. In this section, we address the biotic vagaries that lentil encounters, exploring integrated approaches through conventional and molecular breeding strategies for their holistic management. We delve into the sources of germplasm known for their resistance and tolerance to these stresses followed by their delivery through traditional breeding approaches as well as the identification of essential genes and quantitative trait loci (QTL) necessary for the development of disease-resistant lentil cultivars addressing these issues. The pace of integrating interactome methods of multiomics into breeding efforts and employing advanced tools like genetic engineering and genome editing in lentil has been notably slower. Consequently, there exists significant potential to explore these methodologies, enabling a substantial leap forward in the development of disease-resistant lentil cultivars. We summarize the current status, recent discoveries, and future directions of research towards mitigating biotic stresses in lentil.
Global nighttime temperatures are rising at twice the rate of daytime temperatures and pose a challenge for rice (Oryza sativa) production. High nighttime temperature (HNT) stress affects rice yield by reducing grain weight, size, and fertility. Although the genes associated with these yield parameters have been identified and characterized under normal temperatures, the genetic basis of grain weight regulation under HNT stress remains less explored. We examined the natural variation for rice single grain weight (SGW) under HNT stress imposed during grain development. A genome-wide association analysis identified several loci associated with grain weight under HNT stress. A locus, single grain weight 1 (SGW1), specific to HNT conditions resolved to LONELY GUY-Like 1 (LOGL1), which encodes a putative cytokinin activation enzyme. We demonstrated that LOGL1 contributes to allelic variation at SGW1. Accessions with lower LOGL1 transcript abundance had higher grain weight under HNT. This was supported by higher grain weight of logl1 mutants relative to the wild type under HNT. Compared to logl1 mutants, LOGL1 over-expressers showed increased sensitivity to HNT. We showed that LOGL1 regulates the thiamine biosynthesis pathway, which is under circadian regulation, which in turn is likely perturbed by HNT stress. These findings provide a genetic source to enhance rice adaptation to warming night temperatures and improve our mechanistic understanding of HNT stress tolerance pathways.
Climate change is an ongoing threat worldwide, concerning food security in developing countries but also affecting crop productivity even in well-developed regions. These continuous changes in the climate have a multidimensional and complex impact on food availability and population health, leading to an urge for a science-based approach that can simultaneously take advantage of the new imposed environmental conditions for food productivity and security.
In this context, elevated atmospheric CO2 (eCO2) arises as a flagship in climate change conditions, and despite showing a positive influence on the photosynthesis rate of many C3 species, the C4 species response is relatively small, also occasioning a decrease in proteins, vitamins, and micronutrients content in both metabolisms under certain conditions, reducing nutritional quality. Temperature oscillation also influences crop productivity with complex interactions through ambient CO2 concentration, water availability, and nutrient availability. In the concern of temperature, high day temperature (HDT) and high night temperature (HNT) affect productivity in different ways, making it detrimental to understand how and which crops are affected by each or both temperature variations and in which developmental stage crops are most affected. Furthermore, crop improvement and smart land management are crucial to alleviate the ubiquitous climate change events.
Heat stress (HS) is a major threat to crop productivity and is expected to be more frequent and severe due to climate change challenges. The predicted increase in global temperature requires us to understand the dimensions of HS experienced by plants, particularly during reproductive stages, as crop productivity is majorly dependent on the success of plant reproduction. The impact of HS on crop productivity is relatively less-studied than the other abiotic stresses, such as drought and salinity. Plants have evolved diverse mechanisms to perceive, transduce, respond, and adapt to HS at the molecular, biochemical, and physiological levels. Unraveling these complex mechanisms underlying plant HS response and tolerance would facilitate designing well-informed and effective strategies to engineer HS tolerance in crop plants. In this review, we concisely discuss the molecular impact of HS on plant reproductive processes and yield, with major emphasis on transcription factors. Moreover, we offer vital strategies (encompassing omics studies, genetic engineering and more prominently gene editing techniques) that can be used to engineer transcription factors for enhancing heat tolerance. Further, we highlight critical shortcomings and knowledge gaps in HS tolerance research that should guide future research investigations. Judicious studies and a combination of these strategies could speed up the much-needed development of HS-resilient crop cultivars.
Wheat (Triticum aestivum L.) is a staple food for about 40% of the world's population. As the global population growth and living standards improvement, high yield and improved nutritional quality have become the main targets for wheat breeding. However, wheat production has been compromised by global warming through the more frequent occurrence of extreme temperature events, which increased water scarcity, aggravated soil salinization, and caused the plants more vulnerable to diseases, and can directly reduce plant fertility and suppress yield. One promising option to address these challenges is the genetic improvement of wheat for enhanced resistance to environmental stress. Several decades of progress in genomics and genetic engineering has tremendously advanced our understanding of the molecular and genetic mechanisms underlying abiotic and biotic stress responses in wheat. These advances have heralded what might be considered a "golden age" of functional genomics for the genetic improvement of wheat. Here, we summarize the current knowledge on the molecular and genetic basis of wheat resistance to abiotic and biotic stresses: the QTL/genes involved, their functional and regulatory mechanisms, and related strategies for genetic modification of wheat for improved stress resistance. In addition, we also provide perspectives on some key challenges that need to be addressed.
Heat stress (HS) during grain filling is an extreme environmental factor and affects plant growth and development. Foliar application of exogenous brassinolide (BR) is an effective practice to relieve HS injuries, but the influence on the accumulation and remobilization of biomass and nitrogen is still unclear. In the present study, the effect of foliar BR application at the silking stage on the accumulation and remobilization of biomass and nitrogen in fresh waxy maize under ambient (28/20 °C) and high (35/27 °C) temperatures during grain filling were studied in a phytotron using heat-sensitive Yunuo7 (YN7) and heat-tolerant Jingkenuo2000 (JKN2000) as materials. HS reduced the fresh ear yield by 21.8% and 19.8% in YN7 and JKN2000, respectively, but fresh grain yield was only reduced in the heat-sensitive hybrid (6.9%) and unaffected in the heat-tolerant hybrid. BR application improved the yields of fresh ears (11.3% and 10.9% in YN7 and JKN2000, respectively) and grains (19.9% and 13.2% in YN7 and JKN2000, respectively) under HS, and the increases were higher in YN7. HS decreased the post-silking biomass accumulation by 67.3% and 51.8%, and nitrogen deposition by 61.9% and 50.5%, in YN7 and JKN2000, respectively. The remobilization of pre- and post-silking biomass and nitrogen were increased and decreased by HS in YN7, respectively, but both were unaffected in JKN2000. Under HS, BR application increased the remobilization of post-silking biomass and nitrogen in both hybrids. The grain nitrogen concentration was increased by HS but decreased by BR application in both hybrids. The harvest index of biomass and nitrogen was increased by HS, and it was improved in YN7 and unaffected in JKN2000 by BR application under HS. In conclusion, BR application at the silking stage can relieve HS injuries on fresh waxy maize yields by improving the remobilization of biomass and nitrogen to grain and increasing the harvest index, especially in the heat-sensitive hybrid. Therefore, foliar BR application is a simple, feasible, efficient practice in fresh waxy maize production and is worth popularizing, especially under warmer climates.
High night temperature (HNT) often reduces yield in field crops. In rice, HNT during the ripening stage diminishes endosperm cell size, resulting in a considerable reduction in final kernel weight; however, little is known about the underlying mechanisms at cell level. In this study, we performed picolitre pressure-probe-electrospray-ionization mass spectrometry to directly determine metabolites in growing inner endosperm cells of intact seeds produced under HNT conditions, combining with 13C feeding and water status measurements including in situ turgor assay. Microscopic observation in the inner zone suggested that approximately 24.2% of decrease in cell expansion rate occurred under HNT at early ripening stage, leading to a reduction in cell volume. It has been shown that HNT-treated plants were subjected to mild shoot water deficit at night and endosperm cell turgor was sustained by a decline in osmotic potential. Cell metabolomics also suggests that active solute accumulation was caused by a partial inhibition of wall and starch biosynthesis under HNT conditions. Because metabolites were detected in the single cells, it is concluded that a partial arrest of cell expansion observed in the inner endosperms was caused by osmotic adjustment at mild water deficit during HNT conditions.
Winter wheat (Triticum aestivum L.) is essential to maintain food security for a large proportion of the world’s population. With increased risk from abiotic stresses due to climate variability, it is imperative to understand and minimize the negative impact of these stressors, including high night temperature (HNT). Both globally and at regional scales, a differential rate of increase in day and night temperature is observed, wherein night temperatures are increasing at a higher pace and the trend is projected to continue into the future. Previous studies using controlled environment facilities and small field-based
removable chambers have shown that post-anthesis HNT stress can induce a significant reduction in wheat grain yield. A prototype was previously developed by utilizing field-based tents allowing for simultaneous phenotyping of popular winter wheat varieties from US Midwest and advanced breeding lines. Hence, the objectives of the study were to (i) design and build a new field-based infrastructure and test and validate the uniformity of HNT stress application on a scaled-up version of the prototype (ii) improve and develop a more sophisticated cyber-physical system to sense and impose postanthesis HNT stress uniformly through physiological maturity within the scaled-up tents; and (iii) determine the impact of HNT stress during grain filling on the agronomic and grain quality parameters
including starch and protein concentration. The system imposed a consistent post-anthesis HNT stress of + 3.8 °C until maturity and maintained uniform distribution of stress which was confirmed by (i) 0.23 °C temperature differential between an array of sensors within the tents and (ii) statistically similar performance of a common check replicated multiple times in each tent. On average, a reduction in grain-filling duration by 3.33 days, kernel weight by 1.25% per °C, grain number by 2.36% per °C and yield by 3.58% per °C increase in night temperature was documented. HNT stress induced a significant reduction in starch concentration indicating disturbed carbon balance. The pilot field-based facility integrated with a robust cyber-physical system provides a timely breakthrough for evaluating HNT stress impact on large diversity panels to enhance HNT stress tolerance across field crops. The flexibility of the cyber-physical system and movement capabilities of the field-based infrastructure allows this methodology to be adaptable to different crops.
Understanding plant thermal tolerance is fundamental to predicting impacts of extreme temperature events that are increasing in frequency and intensity across the globe. Extremes, not averages, drive species evolution, determine survival and increase crop performance. To better prioritize agricultural and natural systems research, it is crucial to evaluate how researchers are assessing the capacity of plants to tolerate extreme events. We conducted a systematic review to determine how plant thermal tolerance research is distributed across wild and domesticated plants, growth forms and biomes, and to identify crucial knowledge gaps. Our review shows that most thermal tolerance research examines cold tolerance of cultivated species; c. 5% of articles consider both heat and cold tolerance. Plants of extreme environments are understudied, and techniques widely applied in cultivated systems are largely unused in natural systems. Lastly, we find that lack of standardized methods and metrics compromises the potential for mechanistic insight. Our review provides an entry point for those new to the methods used in plant thermal tolerance research and bridges often disparate ecological and agricultural perspectives for the more experienced. We present a considered agenda of thermal tolerance research priorities to stimulate efficient, reliable and repeatable research across the spectrum of plant thermal tolerance.
Abstract: The wide natural variation present in rice is an important source of genes to facilitate stress tolerance breeding. However, identification of candidate genes from RNA-Seq studies is hampered by the lack of high-quality genome assemblies for the most stress tolerant cultivars. A more targeted solution is the reconstruction of transcriptomes to provide templates to map RNA-seq reads. Here, we sequenced transcriptomes of ten rice cultivars of three subspecies on the PacBio Sequel platform. RNA was isolated from different organs of plants grown under control and abiotic stress conditions in different environments. Reconstructed de novo reference transcriptomes resulted in 37,500 to 54,600 plant-specific high-quality isoforms per cultivar. Isoforms were collapsed to reduce sequence redundancy and evaluated, e.g., for protein completeness (BUSCO). About 40% of all identified transcripts were novel isoforms compared to the Nipponbare reference transcriptome. For the drought/heat tolerant aus cultivar N22, 56 differentially expressed genes in developing seeds were identified at combined heat and drought in the field. The newly generated rice transcriptomes are useful to identify candidate genes for stress tolerance breeding not present in the reference transcriptomes/genomes. In addition, our approach provides a cost-effective alternative to genome sequencing for identification of candidate genes in highly stress tolerant genotypes.
A higher minimum (night‐time) temperature is considered a greater limiting factor for reduced rice yield than a similar increase in maximum (daytime) temperature. While the physiological impact of high night temperature (HNT) has been studied, the genetic and molecular basis of HNT stress response remains unexplored.
We examined the phenotypic variation for mature grain size (length and width) in a diverse set of rice accessions under HNT stress. Genome‐wide association analysis identified several HNT‐specific loci regulating grain size as well as loci that are common for optimal and HNT stress conditions.
A novel locus contributing to grain width under HNT conditions colocalized with Fie1, a component of the FIS‐PRC2 complex. Our results suggest that the allelic difference controlling grain width under HNT is a result of differential transcript‐level response of Fie1 in grains developing under HNT stress.
We present evidence to support the role of Fie1 in grain size regulation by testing overexpression (OE) and knockout mutants under heat stress. The OE mutants were either unaltered or had a positive impact on mature grain size under HNT, while the knockouts exhibited significant grain size reduction under these conditions.
Rice (Oryza sativa) is the main food source for more than 3.5 billion people in the world.
Global climate change is having a strong negative effect on rice production. One of the climatic factors impacting rice yield is asymmetric warming, i.e., the stronger increase in nighttime as compared to daytime temperatures. Little is known of the metabolic responses of rice to high night temperature (HNT) in the field. Eight rice cultivars with contrasting HNT sensitivity were grown in the field during the wet (WS) and dry season (DS) in the Philippines. Plant height, 1000-grain weight and harvest index were influenced by HNT in both seasons, while total grain yield was only consistently reduced in the WS. Metabolite composition was analysed by gas chromatography-mass spectrometry (GC-MS). HNT effects were more pronounced in panicles than in flag leaves. A decreased abundance of sugar phosphates and sucrose, and a higher abundance of monosaccharides in panicles indicated impaired glycolysis and higher respiration-driven carbon losses in response to HNT in the WS. Higher amounts of alanine and cyano-alanine in panicles grown in the DS compared to in those grown in the WS point to an improved N-assimilation and more effective detoxification of cyanide, contributing to the smaller impact of HNT on grain yield in the DS.
Nighttime warming poses a threat to global food security as it is driving yield declines worldwide, but our understanding of the physiological basis of this phenomenon remains very limited. Furthermore, it is often assumed that such declines are driven solely by increases in nighttime temperature (TNight). Here we argue that, in addition to temperature, increases in nighttime evaporative demand may ‘conspire’ to penalize yields and end-use quality traits. We propose an ecophysiological framework outlining the possible mechanistic basis of such declines in yield and quality. We suggest ways to use the proposed framework as a guide to future efforts aimed at alleviating productivity losses by integrating crop ecophysiology with modeling, breeding, and management.
High temperature stress during rice reproductive development results in yield losses. Reduced grain yield and grain quality has been associated with high temperature stress, and specifically with high night-time temperatures (HNT). Characterizing the impact of HNT on the phenotypic and metabolic status of developing rice seeds can provide insights into the mechanisms involved in yield and quality decline. Here, we examined the impact of warmer nights on the morphology and metabolome during early seed development in six diverse rice accessions. Seed size was sensitive to HNT in four of the six genotypes, while seed fertility and seed weight were unaffected. We observed genotypic differences for negative impact of HNT on grain quality. This was evident from the chalky grain appearance due to impaired packaging of starch granules. Metabolite profiles during early seed development (3 and 4 days after fertilization; DAF) were distinct from the early grain filling stages (7 and 10 DAF) under optimal conditions. We observed that accumulation of sugars (sucrose, fructose, and glucose) peaked at 7 DAF suggesting a major flux of carbon into glycolysis, tricarboxylic acid cycle, and starch biosynthesis during grain filling. Next, we determined hyper (HNT > control) and hypo (HNT < control) abundant metabolites and found 19 of the 57 metabolites to differ significantly between HNT and control treatments. The most prominent changes were exhibited by differential abundance of sugar and sugar alcohols under HNT, which could be linked to a protective mechanism against the HNT damage. Overall, our results indicate that combining metabolic profiles of developing grains with yield and quality parameters under high night temperature stress could provide insight for exploration of natural variation for HNT tolerance in the rice germplasm.
Though temperature over the past three decades has shown an asynchronous warming trend between daytime and nighttime, the response of vegetation activity to such non-uniform warming is still not very clear. In this study, the least squares linear trend analysis and geographic information system spatial analysis were conducted to analyze the spatiotemporal patterns of the daytime and nighttime warming based on the daily temperature data from 1982 to 2015 in Northwest China. The normalized difference vegetation index (NDVI) from Global Inventory Monitoring and Modeling System and vegetation type data were used to investigate the responses of vegetation activity to the daytime and nighttime warming using the partial correlation analysis. Our results suggested that (1) there was a very significant increasing trend in both daytime and nighttime temperatures in Northwest China from 1982 to 2015; night temperatures increased about 1.2 times faster than daytime temperatures, showing diurnal asymmetric warming; (2) the responses of vegetation activity to daytime and nighttime warming in Northwest China showed a distinct spatial pattern; the change in night temperatures had a more significant (positive in most regions) effect on vegetation; (3) various types of vegetation responded differently to asymmetric daytime and nighttime warming. Grassland NDVI, broad-leaved, and coniferous forest NDVI significantly responded to daytime warming. Shrub NDVI and desert NDVI significantly responded to night warming. These findings can deepen the understanding of the effects of the daytime and nighttime warming on vegetation activities in arid regions in the context of the current asymmetric warming.
Background
Many agronomic traits have been bred into modern wheat varieties, but wheat (Triticum aestivum L.) continues to be vulnerable to heat stress, with high night-time temperature (HNT) stress shown to have large negative impact on yield and quality. Global mean temperature during the day is consistently warming with the minimum night temperature increasing at a much quicker pace. Currently, there is no system or method that allows crop scientists to impose HNT stress at key developmental stages on wheat or crops in general under field conditions, involving diverse genotypes and maintaining a dynamic temperature differential within the tents compared to the outside.
Results
Through implementation of a side roll up and a top ventilation system, heaters, and a custom cyber-physical system using a Raspberry Pi, the heat tents were able to consistently maintain an elevated temperature through the night to differentiate heat stress impact on different genotypes. When the tents were placed in their day-time setting they were able to maintain ambient day-time temperature without having to be removed and replaced on the plots. Data averaged from multiple sensors over three consecutive weeks resulted in a consistent but small temperature difference of 0.25 °C within the tents, indicating even distribution of heat. While targeting a temperature differential of 4 °C, the tents were able to maintain an average differential of 3.2 °C consistently throughout the night-time heat stress period, compared to the outside ambient conditions. The impact of HNT stress was confirmed through a statistically significant yield reduction in eleven of the twelve genotypes tested. The average yield under HNT stress was reduced by 20.3% compared to the controls, with the highest reduction being 41.4% and a lowest reduction of 6.9%. Recommendations for fine-tuning the system are provided.
Conclusion
This methodology is easily accessible and can be widely utilized due to its flexibility and ease of construction. This system can be modified and improved based on some of the recommendations and has the potential to be used across other crops or plants as it is not reliant on access to any hardwired utilities. The method tested will help the crop community to quantify the impact of HNT stress, identify novel donors that induce tolerance to HNT and help the breeders develop crop varieties that are resilient to changing climate.
Electronic supplementary material
The online version of this article (10.1186/s13007-019-0424-x) contains supplementary material, which is available to authorized users.
Temperatures from 1982 to 2015 have exhibited an asymmetric warming pattern between day and night throughout the Yellow River Basin. The response to this asymmetric warming can be linked to vegetation growth as quantified by the NDVI (Normalized Difference Vegetation Index). In this study, the time series trends of the maximum temperature (Tmax) and the minimum temperature (Tmin) and their spatial patterns in the growing season (April–October) of the Yellow River Basin from 1982 to 2015 were analyzed. We evaluated how vegetation NDVI had responded to daytime and night-time warming, based on NDVI and meteorological parameters (precipitation and temperature) over the period 1982–2015. We found: (1) a persistent increase in the growing season Tmax and Tmin in 1982–2015 as confirmed by using the Mann–Kendall (M–K) non-parametric test method (p < 0.01), where the rate of increase of Tmin was 1.25 times that of Tmax, and thus the diurnal warming was asymmetric during 1982–2015; (2) the partial correlation between Tmax and NDVI was significantly positive only for cultivated plants, shrubs, and desert, which means daytime warming may increase arid and semi-arid vegetation’s growth and coverage, and cultivated plants’ growth and yield. The partial correlation between Tmin and NDVI of all vegetation types except broadleaf forest is very significant (p < 0.01) and, therefore, it has more impacts vegetation across the whole basin. This study demonstrates a methodogy for studying regional responses of vegetation to climate extremes under global climate change.
Cereal yields decrease when grain‐fill proceeds under conditions of prolonged, moderately‐elevated temperatures. Endosperm‐endogenous processes alter both rate and duration of dry‐weight gain, but underlying mechanisms remain unclear. Heat effects could be mediated by either abnormal, premature cessation of storage compound deposition or accelerated implementation of normal development. This study used controlled environments to isolate temperature as the sole environmental variable during Zea mays kernel‐fill, from 12 days after pollination to maturity. Plants subjected to elevated day, elevated night temperatures (38°C day, 28°C night [38/28°C]) or elevated day, normal night (38/17°C), were compared to those from controls grown in normal day and night conditions (28/17°C). Progression of change over time in endosperm tissue was followed to dissect contributions at multiple levels, including transcriptome, metabolome, enzyme activities, product accumulation, and tissue ultrastructure. Integrated analyses indicated that the normal developmental program of endosperm is fully executed under prolonged high‐temperature conditions, but at a faster rate. Accelerated development was observed when both day and night temperatures were elevated, but not whan daytime temperature alone was increased. Although transcripts for most components of glycolysis and respiration were either up‐regulated or minimally affected, elevated temperatures decreased abundance of mRNAs related to biosynthesis of starch and storage proteins. Further analysis of 20 central‐metabolic enzymes revealed six activities that were reduced under high‐temperature conditions, indicating candidate roles in the observed reduction of grain dry weight. Nonetheless, a striking overall resilience of grain‐filling in the face of elevated temperatures can be attributed to acceleration of normal endosperm development.
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Polyamines (PAs) are low molecular weight aliphatic nitrogenous bases containing two or more amino groups. They are produced by organisms during metabolism and are present in almost all cells. Because they play important roles in diverse plant growth and developmental processes and in environmental stress responses, they are considered as a new kind of plant biostimulant. With the development of molecular biotechnology techniques, there is increasing evidence that PAs, whether applied exogenously or produced endogenously via genetic engineering, can positively affect plant growth, productivity, and stress tolerance. However, it is still not fully understood how PAs regulate plant growth and stress responses. In this review, we attempt to cover these information gaps and provide a comprehensive and critical assessment of the published literature on the relationships between PAs and plant flowering, embryo development, senescence, and responses to several (mainly abiotic) stresses. The aim of this review is to summarize how PAs improve plants' productivity, and to provide a basis for future research on the mechanism of action of PAs in plant growth and development. Future perspectives for PA research are also suggested.
Efforts to anticipate how climate change and variability will affect future crop production can benefit from understanding the impacts of current and historic changes. This study aimed to quantify and compare the impact of increased night temperature on potential yield and phenology of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) crops modelled using APSIM with historical climate series (1961–2014) in sites representative of the Argentinean Pampas. For each site, the sowing date was adjusted to avoid frost and heat events at flowering, based on historical probability. The critical period was the more sensitive crop phase (shortened by 0.6 d decade−1) for the observed asymmetric warming; regional minimum temperature trend of ca. 0.14 and 0.16 °C decade−1 in wheat and barley, respectively. Wheat and barley yields declined across the region between ca. 2% and 9% per °C increase in the minimum temperature during the critical period, linked to lower cumulative radiation capture as a result of a shorter crop phase and lower incident radiation due to displacement towards winter. Regional variability in the simulated yield response to the observed night warming was mainly explained by differences the response of incident solar radiation during the critical period to the minimum temperature increase.
Global warming causes a faster increase of night temperature than of day temperature in tropical and subtropical zones. Little is known about the effect of high night temperature on storage lipids and transcriptome changes in oilseed rape. This study compared the total fatty acids and fatty acid compositions in seeds of two oilseed rape cultivars between high and low night temperatures. Their transcriptome profiles were also analyzed. High night temperature significantly affected the total fatty acids and fatty acid compositions in seeds of both low and high oil content cultivars, namely Jiuer-13 and Zheyou-50, thereby resulting in 18.9% and 13.7% total fatty acid reductions, respectively. In particular, high night temperature decreased the relative proportions of C18:0 and C18:1 but increased the proportions of C18:2 and C18:3 in both cultivars. In-depth analysis of transcriptome profiles revealed that high night temperature up-regulated gibberellin signaling during the night-time. This up-regulation was associated with the active expression of genes involved in fatty acid catabolism, such as those in β-oxidation and glyoxylate metabolism pathways. Although the effect of temperature on plant lipids has been previously examined, the present study is the first to focus on night temperature and its effect on the fatty acid composition in seeds.
The genus Oryza is a model system for the study of molecular evolution over time scales ranging from a few thousand to 15 million years. Using 13 reference genomes spanning the Oryza species tree, we show that despite few large-scale chromosomal rearrangements rapid species diversification is mirrored by lineage-specific emergence and turnover of many novel elements, including transposons, and potential new coding and noncoding genes. Our study resolves controversial areas of the Oryza phylogeny, showing a complex history of introgression among different chromosomes in the young 'AA' subclade containing the two domesticated species. This study highlights the prevalence of functionally coupled disease resistance genes and identifies many new haplotypes of potential use for future crop protection. Finally, this study marks a milestone in modern rice research with the release of a complete long-read assembly of IR 8 'Miracle Rice', which relieved famine and drove the Green Revolution in Asia 50 years ago.
Phenylalanine ammonia-lyase (PAL) which is considered to be one of the main lines of cell acclimation against stress in plants, non-structural carbohydrates (NSC) accumulation and chlorophyll fluorescence parameters were quantified in two rice genotypes as a function of two temperature regimes: 22/30 °C (control) and 28/30 °C night/day (high night temperatures - HNT), imposed from heading to milk stage. The rice cultivars chosen were Nagina22 (N22) and BRS Querência (BRS-Quer), which are genotypes tolerant and sensitive to high temperatures, respectively. BRS-Quer genotype highlighted more sensitive responses maintaining higher PAL and peroxidase levels on seventh and twenty-first days after stress imposing. On the other hand, this genotype showed levels of fructose, glucose and sucrose decreasingly across stress period whether compared to N22. Both genotypes showed similarity for most of the chlorophyll fluorescence parameters. However, the photosynthesis induction curve highlighted that HNT caused decreases in some photochemical quenching of fluorescence as well as increases of non-phochemical quenching, affecting more prominently BRS-Quer genotype. N22 maintained unaltered the spikelet sterility and 1000-grain weight across temperature regimes showing a consistent trend with its stem NSC accumulation during stress period. The higher availability of soluble sugars shown by N22 at the end of stress period could be unloaded in spikelet formation and grain fillings contributing in their lower sterility rate and greater 1000-grain weight stability across the environments. These results indicate that selecting genotypes with higher capacity to stem NSC translocation beyond accumulation at HNT could lead to more grain yield stability in future climate scenarios.
Rice production is challenged by the asymmetric increases in day and night temperatures. Efforts are required to improve our understanding of the impact of climate change on rice production. To this end, 2-year experiment was conducted to evaluate the response of mid-season rice growth in the central and southern regions of China to elevated temperatures. Four replicates of four widely planted indica rice cultivars (Huanghuazhan: HHZ; Shanyou63: SY63; Yangliangyou6: YLY6; Liangyoupeijiu: LYPJ) were subjected to four elevated-temperature treatments (control: ambient temperature; NW: night-time warming; DW: daytime warming; AW: all-day warming) generated by an open-top hot-blast system under field conditions. This apparatus causes an ~2°C increase in the rice canopy temperature. Of all the elevated-temperature treatments, AW was the most devastating treatment for all rice cultivars, negatively affecting nearly all of investigated parameters, including grain yield and its components, dry matter accumulation, biomass, and harvest index (HI). The AW treatment decreased the grain yield by 11–35% and 43–78% in 2015 and 2016, respectively. No significant reduction in the grain yield was observed in the DW and NW treatments in 2015. However, the grain yield was decreased in DW and NW treatments by 20–52% and 18–55%, respectively, in 2016. Furthermore, the temperature-driven degradation of pollen viability, the number of pollen grains adhering to the stigma and pollen germination on the stigma caused spikelet sterility and thereby decreased the grain yield. The YLY6 and SY63 cultivars performed better than the HHZ and LYPJ cultivars with respect to grain yield and its components in all elevated-temperature treatments in both years. However, 42.97 and 61.01% reductions still occurred for the SY63 and YLY6 cultivars, respectively, in the AW treatment in 2016. The above results suggested that the elevated temperature may cause a noteworthy reduction in the productions of these widely planted genotypes in central and southern regions of China. To ensure the security of rice production in this region in an expected global warming environment, currently planted varieties will need to be replaced by heat-resistant varieties in the future.
Rice grain yield and quality are predicted to be highly vulnerable to global warming. Five genotypes including heat-tolerant and susceptible checks, a heat-tolerant near-isogenic line and two hybrids were exposed to control (31 °C/23 °C, day/night), high night-time temperature (HNT; 31 °C/30 °C), high day-time temperature (HDT; 38 °C/23 °C) and high day- and night-time temperature (HNDT; 38 °C/30 °C) treatments for 20 consecutive days during the grain-filling stage. Grain-filling dynamics, starch metabolism enzymes, temporal starch accumulation patterns and the process of chalk formation were quantified. Compensation between the rate and duration of grain filling minimized the impact of HNT, but irreversible impacts on seed-set, grain filling and ultimately grain weight were recorded with HDT and HNDT. Scanning electron microscopy demonstrated irregular and smaller starch granule formation affecting amyloplast build-up with HDT and HNDT, while a quicker but normal amylopast build-up was recorded with HNT. Our findings revealed temporal variation in the starch metabolism enzymes in all three stress treatments. Changes in the enzymatic activity did not derail starch accumulation under HNT when assimilates were sufficiently available, while both sucrose supply and the conversion of sucrose into starch were affected by HDT and HNDT. The findings indicate differential mechanisms leading to high day and high night temperature stress-induced loss in yield and quality. Additional genetic improvement is needed to sustain rice productivity and quality under future climates.
The diurnal and seasonal temperature rising patterns “asymmetric warming,” plays an important role in crop distribution and productivity. Asymmetric warming during the early growth periods of winter wheat (Triticum aestivum L.) profoundly affects vegetative growth and post-anthesis grain productivity, but the underlying physiological mechanism is still unclear. We conducted field experiments from 2012 to 2014 using two wheat cultivars, namely, Yangmai-13 (vernal type) and Yannong-19 (semi-winter type), to investigate the influences of night-warming during the winter (warming by 1.56–1.67°C from tillering to jointing) or during the spring (warming by 1.78–1.92°C from jointing to booting) on post-anthesis physiological activities and grain-filling processes. Both night-warming treatments enhanced the source activity by increasing flag leaf area, chlorophyll content, and photosynthetic capability in both cultivars compared with those of the control. The night-warming treatments caused an increase in the antioxidant activities of superoxide dismutase (SOD), peroxidase, and catalase (CAT) in the flag leaves of both cultivars, while ROS contents such as superoxide anion radical (O2•−) and hydrogen peroxide (H2O2) decreased. Moreover, the expression levels of Rubisco activase B (RcaB), major chlorophyll a/b-binding protein (Cab), chloroplast Cu/Zn superoxide dismutase (Cu/Zn-SOD), mitochondrial manganese superoxide dismutase (Mn-SOD), and CAT genes were upregulated at anthesis and were associated with higher photosynthetic capacity and antioxidant activities. Furthermore, night-warming improved sink activities by increasing the concentrations of grain indole-3-acetic acid and cytokinins as well as the sucrose synthase activity for both cultivars. Winter night-warming showed greater potential for improving source strength and grain filling, with consistent performance in both cultivars compared with that of spring night-warming. We concluded form these results that night-warming can improve source and sink capacities in winter wheat, and winter night-warming has greater advantages in this respect than does spring warming.
Cytokinins (CTKs) regulate panicle size and mediate heat tolerance in crops. To investigate the effect of high temperature on panicle CTK expression and the role of such expression in panicle differentiation in rice, four rice varieties (Nagina22, N22; Huanghuazhan, HHZ; Liangyoupeijiu, LYPJ; and Shanyou63, SY63) were grown under normal conditions and subjected to three high temperature treatments and one control treatment in temperature-controlled greenhouses for 15 days during the early reproductive stage. The high temperature treatments significantly reduced panicle CTK abundance in heat-susceptible LYPJ, HHZ, and N22 varieties, which showed fewer spikelets per panicle in comparison with control plants. Exogenous 6-benzylaminopurine application mitigated the effect of heat injury on the number of spikelets per panicle. The high temperature treatments significantly decreased the xylem sap flow rate and CTK transportation rate, but enhanced cytokinin oxidase/dehydrogenase (CKX) activity in heat-susceptible varieties. In comparison with the heat-susceptible varieties, heat-tolerant variety SY63 showed less reduction in panicle CTK abundance, an enhanced xylem sap flow rate, an improved CTK transport rate, and stable CKX activity under the high temperature treatments. Enzymes involved in CTK synthesis (isopentenyltransferase, LONELY GUY, and cytochrome P450 monooxygenase) were inhibited by the high temperature treatments. Heat-induced changes in CTK transportation from root to shoot through xylem sap flow and panicle CTK degradation via CKX were closely associated with the effects of heat on panicle CTK abundance and panicle size. Heat-tolerant variety SY63 showed stable panicle size under the high temperature treatments because of enhanced transport of root-derived CTKs and stable panicle CKX activity. Our results provide insight into rice heat tolerance that will facilitate the development of rice varieties with tolerance to high temperature.
Land surface temperature over the past decades has shown a faster warming trend during the night than during the day. Extremely low night temperatures have occurred frequently due to the influence of land-sea thermal difference, topography and climate change. This asymmetric night temperature change is expected to affect plant ecophysiology and growth, as the plant carbon consumption processes could be affected more than the assimilation processes because photosynthesis in most plants occurs during the daytime whereas plant respiration occurs throughout the day. The effects of high night temperature (HNT) and low night temperature (LNT) on plant ecophysiological and growing processes and how the effects vary among different plant functional types (PFTs) have not been analyzed extensively. In this meta-analysis, we examined the effect of HNT and LNT on plant physiology and growth across different PFTs and experimental settings. Plant species were grouped according to their photosynthetic pathways (C3, C4, and CAM), growth forms (herbaceous, woody), and economic purposes (crop, non-crop). We found that HNT and LNT both had a negative effect on plant yield, but the effect of HNT on plant yield was primarily related to a reduction in biomass allocation to reproduction organs and the effect of LNT on plant yield was more related to a negative effect on total biomass. Leaf growth was stimulated at HNT and suppressed at LNT. HNT accelerated plants ecophysiological processes, including photosynthesis and dark respiration, while LNT slowed these processes. Overall, the results showed that the effects of night temperature on plant physiology and growth varied between HNT and LNT, among the response variables and PFTs, and depended on the magnitude of temperature change and experimental design. These findings suggest complexities and challenges in seeking general patterns of terrestrial plant growth in HNT and LNT. The PFT specific responses of plants are critical for obtaining credible predictions of the changes in crop production, plant community structure, vegetation dynamics, biodiversity, and ecosystem functioning of terrestrial biomes when asymmetric night temperature change continues.
Heat stress causes morphological and physiological changes and reduces crop yield in rice (Oryza sativa). To investigate changes in phytohormones and their relationships with yield and other attributes under heat stress, four rice varieties (Nagina22, Huanghuazhan, Liangyoupeijiu, and Shanyou 63) were grown in pots and subjected to three high temperature treatments plus control in temperature-controlled greenhouses for 15 d during the early reproductive phase. Yield reductions in Nagina22, Huanghuazhan, and Liangyoupeijiu were attributed to reductions in spikelet fertility, spikelets per panicle, and grain weight. The adverse effects of high temperature were alleviated by application of exogenous 6-benzylaminopurine (6-BA) in the heat-susceptible Liangyoupeijiu. High temperature stress reduced active cytokinins, gibberellin A1 (GA1), and indole-3-acetic acid (IAA), but increased abscisic acid (ABA) and bound cytokinins in young panicles. Correlation analyses and application of exogenous 6-BA revealed that high temperature-induced cytokinin changes may regulate yield components by modulating the differentiation and degradation of branches and spikelets, panicle exsertion, pollen vigor, anther dehiscence, and grain size. Heat-tolerant Shanyou 63 displayed minor changes in phytohormones, panicle formation, and grain yield under high temperature compared with those of the other three varieties. These results suggest that phytohormone changes are closely associated with yield formation, and a small reduction or stability in phytohormone content is required to avoid large yield losses under heat stress.
High-temperature stress degrades the grain quality of rice; nevertheless, the exogenous application of plant growth regulators (PGRs) might alleviate the negative effects of high temperatures. In the present study, we investigated the responses of rice grain quality to exogenously applied PGRs under high day temperatures (HDT) and high night temperatures (HNT) under controlled conditions. Four different combinations of ascorbic acid (Vc), alpha-tocopherol (Ve), brassinosteroids (Br), methyl jasmonates (MeJA) and triazoles (Tr) were exogenously applied to two rice cultivars (IR-64 and Huanghuazhan) prior to the high-temperature treatment. A Nothing applied Control (NAC) was included for comparison. The results demonstrated that high-temperature stress was detrimental for grain appearance and milling qualities and that both HDT and HNT reduced the grain length, grain width, grain area, head rice percentage and milled rice percentage but increased the chalkiness percentage and percent area of endosperm chalkiness in both cultivars compared with ambient temperature (AT). Significantly higher grain breakdown, set back, consistence viscosity and gelatinization temperature, and significantly lower peak, trough and final viscosities were observed under high-temperature stress compared with AT. Thus, HNT was more PLOS ONE |
Abiotic stresses including drought, salinity, heat, cold, flooding, and ultraviolet radiation causes crop losses worldwide. In recent times, preventing these crop losses and producing more food and feed to meet the demands of ever-increasing human populations have gained unprecedented importance. However, the proportion of agricultural lands facing multiple abiotic stresses is expected only to rise under a changing global climate fueled by anthropogenic activities. Identifying the mechanisms developed and deployed by plants to counteract abiotic stresses and maintain their growth and survival under harsh conditions thus holds great significance. Recent investigations have shown that phytohormones, including the classical auxins, cytokinins, ethylene, and gibberellins, and newer members including brassinosteroids, jasmonates, and strigolactones may prove to be important metabolic engineering targets for producing abiotic stress-tolerant crop plants. In this review, we summarize and critically assess the roles that phytohormones play in plant growth and development and abiotic stress tolerance, besides their engineering for conferring abiotic stress tolerance in transgenic crops. We also describe recent successes in identifying the roles of phytohormones under stressful conditions. We conclude by describing the recent progress and future prospects including limitations and challenges of phytohormone engineering for inducing abiotic stress tolerance in crop plants.
The observed warming of the surface air temperature (SAT) over the last 50 years has not been homogenous. There are strong differences in the temperature changes both geographically and on different time frames. Here, we review the observed diurnal asymmetry in the global warming trend: the night-time temperatures have increased more rapidly than day-time temperatures. Several explanations for this asymmetric warming have been offered in the literature. These generally relate differences in the temperature trends to regionalized feedback effects, such as changes to cloud cover, precipitation or soil moisture. Here, we discuss a complementary mechanism through which the planetary boundary layer (PBL) modulates the SAT response to changes in the surface energy balance. This reciprocal relationship between boundary-layer depth and temperature response can explain a part of why the night-time has warmed more rapidly than the daytime. We used a multi-linear regression model to compare the effect of the PBL, cloud cover, precipitation and soil moisture on the SAT. From this, we demonstrate that it is the boundary-layer depth which is the strongest predictor of the strength of temperature trends in the boreal annual cycle, and in all seasons except the summer.
This paper provides a first overview of the performance of state-of-the-art global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating climate extremes indices defined by the Expert Team on Climate Change Detection and Indices (ETCCDI), and compares it to that in the previous model generation (CMIP3). For the first time, the indices based on daily temperature and precipitation are calculated with a consistent methodology across multimodel simulations and four reanalysis data sets (ERA40, ERA-Interim, NCEP/NCAR, and NCEP-DOE) and are made available at the ETCCDI indices archive website. Our analyses show that the CMIP5 models are generally able to simulate climate extremes and their trend patterns as represented by the indices in comparison to a gridded observational indices data set (HadEX2). The spread amongst CMIP5 models for several temperature indices is reduced compared to CMIP3 models, despite the larger number of models participating in CMIP5. Some improvements in the CMIP5 ensemble relative to CMIP3 are also found in the representation of the magnitude of precipitation indices. We find substantial discrepancies between the reanalyses, indicating considerable uncertainties regarding their simulation of extremes. The overall performance of individual models is summarized by a "portrait" diagram based on root-mean-square errors of model climatologies for each index and model relative to four reanalyses. This metric analysis shows that the median model climatology outperforms individual models for all indices, but the uncertainties related to the underlying reference data sets are reflected in the individual model performance metrics. Key PointsWe calculate indices in a consistent manner across models and reanalysesMulti-model ensembles compare reasonably well with observation-based indicesThere are large uncertainties in the representation of extremes in reanalyses
Forecasting the effects of climate change on nitrogen (N) cycling in pastures requires an understanding of changes in tissue N. We examined the effects of elevated atmospheric CO2 concentration, atmospheric warming and simulated grazing (clipping frequency) on above and belowground tissue N concentrations and C:N ratios of a C3 pasture grass. Phalaris aquatica L. cv "Holdfast" was grown in the field in six transparent temperature gradient tunnels (18 m x 1.5 m x 1.5 m each), three at ambient atmospheric CO2 and three at 759 ppm CO2. Within each tunnel there were three air temperature treatments; ambient control, +2.2 / +4.0 (o)C above ambient day/night warming, and +3.0 (o)C continuous warming. A frequent and an infrequent clipping treatment were applied to each warming x CO2 combination. Green leaf N concentrations were decreased by elevated CO2 and increased by more frequent clipping. Both warming treatments increased leaf N concentrations under ambient CO2 concentrations, but did not significantly alter leaf N concentrations under elevated CO2 concentrations. Nitrogen resorption from leaves was decreased under elevated CO2 conditions as well as by more frequent clipping. Fine root nitrogen concentrations decreased strongly with increasing soil depth and were further decreased at the 10-60 cm soil depths by elevated CO2 concentrations. The interaction between the CO2 and warming treatments showed that leaf N concentration was affected in a non-additive manner. Changes in leaf C:N ratios were driven by changes in N concentration. Overall, the effects of CO2, warming and clipping treatments on aboveground tissue nitrogen concentrations were much greater than on belowground tissue.
Published by Oxford University Press on behalf of the Annals of Botany Company.
Global climate change combined with asymmetric warming can have detrimental effects on the yield of crop plants such as rice (Oryza sativa L.). Little is known about metabolic responses of rice to high night temperature (HNT) conditions. Twelve cultivars with different HNT sensitivity were used to investigate metabolic changes in the vegetative stage under HNT compared to control conditions. Central metabolism, especially TCA cycle and amino acid biosynthesis, were strongly affected particularly in sensitive cultivars. Levels of several metabolites were correlated with HNT sensitivity. Furthermore, pool sizes of some metabolites negatively correlated with HNT sensitivity under control conditions, indicating metabolic pre-adaptation in tolerant cultivars. The polyamines putrescine, spermidine and spermine showed increased abundance in sensitive cultivars under HNT conditions. Correlations between the content of polyamines and 75 other metabolites indicated metabolic shifts from correlations with sugar-phosphates and 1-kestose under control to correlations with sugars and amino and organic acids under HNT conditions. Increased expression levels of ADC2 and ODC1, genes encoding enzymes catalysing the first committed steps of putrescine biosynthesis, were restricted to sensitive cultivars under HNT. Additionally, transcript levels of eight polyamine biosynthesis genes were correlated with HNT sensitivity. Responses to HNT in the vegetative stage result in distinct differences between differently responding cultivars with a dysregulation of central metabolism and an increase of polyamine biosynthesis restricted to sensitive cultivars under HNT conditions and a pre-adaptation of tolerant cultivars already under control conditions with higher levels of potentially protective compatible solutes.
© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.
Warmer climates are already contributing to significant decreases in wheat (Triticum spp.) yields worldwide, highlighting the need for more adapted germplasm. Although many studies have addressed the effects of warmer climates on grain physiology and photosynthesis, only a few have considered temperature effects on other key yield-related traits such as the sensitivity of transpiration rate (TR) to vapour pressure deficit (VPD) − a function of air temperature and relative humidity. In wheat, no reports are available to document such influences. More importantly, the relative contributions of heat-stress night and day conditions on such sensitivity and the plant’s evaporative surface remain to be investigated. The objective of this study was to assess the response of these two physiological processes to long-term (i.e. 3 weeks) exposures to six warming scenarios, consisting of a combination of three target growth-period VPD (2, 2.7 and 4 kPa), and two night temperature (20 and 30°C) regimes among 11 diverse bread and durum wheat lines having different origins. The study revealed (i) a large genetic variability in those responses; (ii) non-linear interactions between the effects of day and night conditions; and (iii) compensation mechanisms between leaf areas and transpiration sensitivities to VPD together with differential acclimation strategies of these sensitivities with respect to increasingly warmer scenarios. These findings open the way to implementing breeding strategies that can improve wheat yields under different warming scenarios.
Growth of cool-season grasses declines with increasing temperatures. The objective of this study was to determine the effects of elevated night temperature on turf quality, root mortality, and carbohydrate metabolism in creeping bentgrass (Agrostis stoloniferous L. var. palustris (Huds.) Farw (syn. A. palustris (Huds.). Plants of 'Penncross' were exposed to two night temperature regimes: 24 degreesC (higher night temperature); and 19 degreesC (lower temperature control) under the same day temperature (24 degreesC) in growth chambers for 45 days. Prolonged exposure of plants to higher night temperature reduced turf quality, canopy photosynthetic rate, whole-plant and root respiration rates during the day, translocation of newly fixed C-14 assimilate to roots, and total nonstructural carbohydrate content in shoots and roots (including dead and live roots). Elevated night temperature increased root mortality and whole-plant and root respiration rates at night. Our results indicated that a decline in turf quality and increase in root dieback with high night temperature was mainly associated with increased night respiration rates of whole plant and roots and reduced carbohydrate availability.
High night temperature (HNT) causes substantial yield loss in rice (Oryza sativa L.). In this study, the physiological processes related to flag leaf dark respiration (Rn) and grain filling under HNT were explored in a multi‐parent advanced generation intercross population developed for heat tolerance (MAGICheat) along with selected high temperature tolerant breeding lines developed with heat‐tolerant parents. Within a subset of lines, flag leaf Rn under HNT treatment was related to lower spikelet number per panicle and thus reduced yield. HNT enhanced the night‐time reduction of non‐structural carbohydrates (NSC) in stem tissue, but not in leaves, and stem night‐time NSC reduction was negatively correlated with yield. Between heading and harvest, the major difference in NSC concentration was found for starch, but not for soluble sugar. HNT weakened the relationship between NSC remobilization and harvest index at both the phenotypic and genetic level. By using genome wide association studies (GWAS), an invertase inhibitor, MADS box transcription factors and a UDP‐glycosyltransferase that were identified as candidate genes orchestrating stem NSC remobilization in the control treatment were lost under HNT. With the identification of physiological and genetic components related to rice HNT response, this study offers promising prebreeding materials and trait targets to sustain yield stability under climate change.
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Rapid increases in minimum night temperature than in maximum day temperature is predicted to continue, posing significant challenges to crop productivity. Rice and wheat are two major staples that are sensitive to high night temperature (HNT) stress. This review aims to (i) systematically compare the grain yield responses of rice and wheat exposed to HNT stress across scales, and (ii) understand physiological and biochemical responses that affect grain yield and quality. To achieve this, we combined a synthesis of current literature on HNT effects on rice and wheat with information from a series of independent experiments we conducted across scales, using a common set of genetic materials to avoid confounding our findings with differences in genetic background. In addition, we explored HNT induced alterations in physiological mechanisms including carbon balance, source‐sink metabolite changes, and reactive oxygen species. Impact of HNT on grain developmental dynamics focused on grain‐filling duration, post‐flowering senescence, changes in grain starch and protein composition, starch metabolism enzymes, and chalk formation in rice grains are summarized. Finally, we highlight the need for high‐throughput field‐based phenotyping facilities for improved assessment of large diversity panels and mapping populations to aid breeding for increased resilience to HNT in crops.
Increasing temperatures resulting from climate change dramatically impact rice crop production in Asia. Depending on the specific stage of rice development, heat stress reduces tiller/panicle number, decreases grain number per plant and lower grain weight, thus negatively impacting yield formation. Hence improving rice crop tolerance to heat stress in terms of sustaining yield stability under high day temperature (HDT), high night temperature (HNT) or combined high day and night temperature (HDNT) will bolster future food security. In this review article we highlight the phenological alterations caused by heat and the underlying molecular‐physiological and genetic mechanisms operating under different types of heat conditions (HDT, HNT and HDNT) to understand heat tolerance. Based on our synthesis of HDT, HNT and HDNT effects on rice yield components, we outline future breeding strategies to contribute to sustained food security under climate change. This article is protected by copyright. All rights reserved.
Unlike sporadic day‐time heat spikes, a consistent increase in night‐time temperatures can potentially derail the genetic gains being achieved. Ten winter wheat genotypes were exposed to six different night‐time temperatures (15°C to 27°C) during flowering and grain‐filling stages in controlled environment chambers. We identified night‐time temperature of 23oC as the critical threshold beyond which a consistent decline in yield and quality was observed. Confocal laser scanning micrographs of central endosperm, bran and germ tissue displayed differential accumulation of protein, lipid and starch with increasing night‐time temperatures. KS07077M‐1 recorded a decrease in starch and increase in protein and lipid in central endosperm with increasing night‐time temperatures, while the same was significantly lower in SY Monument. Expression analysis of genes encoding 21 enzymes (including isoforms) involved in grain‐starch metabolism in developing grains, revealed high night‐time temperature (HNT) induced reduction in transcript levels of ADP‐glucose pyrophosphorylase small subunit involved in starch synthesis and a ≥ 2‐fold increase in starch degrading enzymes isoamylase III, alpha‐ and beta‐amylase. The identified critical threshold, grain compositional changes and the key enzymes in grain starch metabolism that lead to poor starch accumulation in grains establish the foundational knowledge for enhancing HNT tolerance in wheat.
Carbon loss under high night‐time temperature (HNT) leads to significant reduction in wheat yield. Growth chamber studies were carried out using six winter wheat genotypes, to unravel post‐heading HNT (23oC) induced alterations in carbon balance, source‐sink metabolic changes, yield and yield related traits compared to control (15oC) conditions. Four of the six tested genotypes recorded a significant increase in night respiration after four days of HNT exposure, with all the cultivars regulating carbon loss and demonstrating different degree of acclimation to extended HNT exposure. Metabolite profiling indicated carbohydrate metabolism in spikes and activation of the TriCarboxylic Acid (TCA) cycle in leaves as important pathways operating under HNT exposure. A significant increase in sugars, sugar‐alcohols, and phosphate in spikes of the tolerant genotype (Tascosa) indicated osmolytes and membrane protective mechanisms acting against HNT damage. Enhanced night respiration under HNT resulted in higher accumulation of TCA cycle intermediates like isocitrate and fumarate in leaves of the susceptible genotype (TX86A5606). Lower grain number due to lesser productive spikes and reduced grain weight due to shorter grain‐filling duration determined HNT induced yield loss in winter wheat. Traits and mechanisms identified will help catalyze the development of physiological and metabolic markers for breeding HNT‐tolerant wheat.
Potato is an important staple food with increasing popularity worldwide. Elevated temperatures significantly impair tuber yield and quality. Breeding heat‐tolerant cultivars is therefore an urgent need to ensure sustainable potato production in the future. An integrated approach combining physiology, biochemistry and molecular biology was undertaken to contribute to a better understanding of heat effects on source‐ (leaves) and sink‐organs (tubers) in a heat‐susceptible cultivar. An experimental set up was designed allowing tissue‐specific heat application. Elevated day and night (29°/27°C) temperatures impaired photosynthesis and assimilate production. Biomass allocation shifted away from tubers towards leaves indicating reduced sink strength of developing tubers. Reduced sink strength of tubers was paralleled by decreased sucrose synthase activity and expression under elevated temperatures. Heat‐mediated inhibition of tuber growth coincided with a decreased expression of the phloem‐mobile tuberisation signal SP6A in leaves. SP6A expression and photosynthesis were also affected, when only the belowground space was heated, while leaves were kept under control conditions. By contrast, the negative effects on tuber metabolism were attenuated, when only the shoot was subjected to elevated temperatures. This, together with transcriptional changes discussed, indicated a bidirectional communication between leaves and tubers to adjust the source capacity and/or sink strength to environmental conditions.
Cytokinins (CTKs) regulate panicle size and mediate heat tolerance in crops. To
investigate the effect of high temperature on panicle CTK expression and the role
of such expression in panicle differentiation in rice, four rice varieties (Nagina22,
N22; Huanghuazhan, HHZ; Liangyoupeijiu, LYPJ; and Shanyou63, SY63) were grown
under normal conditions and subjected to three high temperature treatments and
one control treatment in temperature-controlled greenhouses for 15 days during
the early reproductive stage. The high temperature treatments significantly reduced
panicle CTK abundance in heat-susceptible LYPJ, HHZ, and N22 varieties, which
showed fewer spikelets per panicle in comparison with control plants. Exogenous
6-benzylaminopurine application mitigated the effect of heat injury on the number
of spikelets per panicle. The high temperature treatments significantly decreased
the xylem sap flow rate and CTK transportation rate, but enhanced cytokinin
oxidase/dehydrogenase (CKX) activity in heat-susceptible varieties. In comparison
with the heat-susceptible varieties, heat-tolerant variety SY63 showed less reduction
in panicle CTK abundance, an enhanced xylem sap flow rate, an improved CTK
transport rate, and stable CKX activity under the high temperature treatments. Enzymes
involved in CTK synthesis (isopentenyltransferase, LONELY GUY, and cytochrome P450
monooxygenase) were inhibited by the high temperature treatments. Heat-induced
changes in CTK transportation from root to shoot through xylem sap flow and panicle
CTK degradation via CKX were closely associated with the effects of heat on panicle
CTK abundance and panicle size. Heat-tolerant variety SY63 showed stable panicle size
under the high temperature treatments because of enhanced transport of root-derived
CTKs and stable panicle CKX activity. Our results provide insight into rice heat tolerance
that will facilitate the development of rice varieties with tolerance to high temperature.
Transitory starch plays a vital role in maintenance respiration as its degradation products provide substrate for the night respiration. A study was conducted with two contrasting rice cultivars: Vandana (high night temperature susceptible) and Nagina 22 (high night temperature tolerant) by subjecting them to increase in transition temperature from anthesis to physiological maturity. Night respiration on plant area basis increased by 35% in Vandana at 5 days after anthesis but was unaffected in tolerant cultivar. A simultaneous 18% decrease in starch content was observed in the susceptible cultivar. An analysis of the starch-metabolizing enzymes showed that activity of β-amylase increased markedly in Vandana whereas both β and α-amylase decreased in Nagina 22 following high day to night transition temperature exposure. The level of starch breakdown product, maltose, increased in the susceptible cultivar but glucose levels declined in both the cultivars. Concurrently, expression of chloroplastic isoforms α-amylase OsAMY1, OsAMY2 and β-amylase OsBAM2 increased in Vandana. A lower accumulation of dry matter was recorded in the susceptible than the tolerant cultivar. Our study elucidated the regulatory role of transitory starch in supporting the high day to night transition temperature-induced night-time respiration which is mediated by the increased activity of β-amylase through enhanced expression of OsBAM2 in flag leaves of susceptible cultivar.
Transcript and metabolite profiling were performed on leaves from six rice cultivars under high night temperature (HNT) condition. Six genes were identified as central for HNT response encoding proteins involved in transcription regulation, signal transduction, protein-protein interactions, jasmonate response, and the biosynthesis of secondary metabolites. Sensitive cultivars showed specific changes in transcript abundance including abiotic stress responses, changes of cell wall related genes, of ABA signaling and secondary metabolism. Additionally, metabolite profiles revealed a highly activated TCA cycle under HNT and concomitantly increased levels in pathways branching off that could be corroborated by enzyme activity measurements. Integrated data analysis using clustering based on one-dimensional self-organizing maps identified two profiles highly correlated with HNT sensitivity. The sensitivity profile included genes of the functional bins abiotic stress, hormone metabolism, cell wall, signaling, redox state, transcription factors, secondary metabolites and defense genes. In the tolerance profile similar bins were affected with slight differences in hormone metabolism and transcription factor responses. Metabolites of the two profiles revealed involvement of GABA signaling, thus providing a link to the TCA cycle status in sensitive cultivars and of myo-inositol as precursor for inositol phosphates linking jasmonate signaling to the HNT response specifically in tolerant cultivars. This article is protected by copyright. All rights reserved.
High night temperature (HNT) is a major constraint to sustaining global rice production under future climate. Physiological and biochemical mechanisms were elucidated for HNT-induced grain yield and quality loss in rice. Contrasting rice cultivars (N22, tolerant; Gharib, susceptible; IR64, high yielding with superior grain quality) were tested under control (23 °C) and HNT (29 °C) using unique field based tents from panicle initiation till physiological maturity. HNT affected 1000 grain weight, grain yield, grain chalk and amylose content in Gharib and IR64. HNT increased night respiration accounted for higher carbon losses during post-flowering phase. Gharib and IR64 recorded 16% and 9% yield reduction with a 63% and 35% increase in average post-flowering Rn under HNT, respectively. HNT altered sugar accumulation in the rachis and spikelets across the cultivars with Gharib and IR64 recording higher sugar accumulation in the rachis. HNT reduced panicle starch content in Gharib (22%) and IR64 (11%) at physiological maturity, but not in the tolerant N22. At the enzymatic level, HNT reduced sink strength with lower cell wall invertase and sucrose synthase activity in Gharib and IR64 which affected starch accumulation in the developing grain reducing grain weight and quality. Interestingly, N22 recorded lower Rn mediated carbon losses and minimum impact on sink strength under HNT. Mechanistic responses identified will facilitate crop models to precisely estimate HNT induced damage under future warming scenarios.
The phenology of spring leaf unfolding plays a key role in the structure and functioning of ecosystems. The classical concept of heat requirement (growing degree days) for leaf unfolding was developed hundreds of years ago, but this model does not include the recently reported greater importance of daytime than night‐time temperature.
A manipulative experiment on daytime vs night‐time warming with saplings of three species of temperate deciduous trees was conducted and a Bayesian method was applied to explore the different effects of daytime and night‐time temperatures on spring phenology.
We found that both daytime and night‐time warming significantly advanced leaf unfolding, but the sensitivities to increased daytime and night‐time temperatures differed significantly. Trees were most sensitive to daytime warming (7.4 ± 0.9, 4.8 ± 0.3 and 4.8 ± 0.2 d advancement per degree Celsius warming (d °C ⁻¹ ) for birch, oak and beech, respectively) and least sensitive to night‐time warming (5.5 ± 0.9, 3.3 ± 0.3 and 2.1 ± 0.9 d °C ⁻¹ ). Interestingly, a Bayesian analysis found that the impact of daytime temperature on leaf unfolding was approximately three times higher than that of night‐time temperatures.
Night‐time global temperature is increasing faster than daytime temperature, so model projections of future spring phenology should incorporate the effects of these different temperatures.
High CO2 and high temperature have an antagonistic interaction effect on rice yield potential and present a unique challenge to adapting rice to projected future climates. Understanding how the differences in response to these two abiotic variables are partitioned across rice germplasm accessions may be key to identifying potentially useful sources of resilient alleles for adapting rice to climate change. In this study, we evaluated eleven globally diverse rice accessions under controlled conditions at two carbon dioxide concentrations (400 and 600 ppm) and four temperature environments (29°C day/21°C night; 29°C day/21°C night with additional heat stress at anthesis; 34°C day/26°C night; and 34°C day/26°C night with additional heat stress at anthesis) for a suite of traits including five yield components, five growth characteristics, one phenological trait, and four photosynthesis-related measurements. Multivariate analyses of mean trait data from these eight treatments divide our rice panel into two primary groups consistent with the genetic classification of INDICA/INDICA-like and JAPONICA populations. Overall, we find that the productivity of plants grown under elevated [CO2 ] was more sensitive (negative response) to high temperature stress compared with that of plants grown under ambient [CO2 ] across this diversity panel. We report differential response to CO2 x temperature interaction for INDICA/INDICA-like and JAPONICA rice accessions and find preliminary evidence for the beneficial introduction of exotic alleles into cultivated rice genomic background. Overall, these results support the idea of using wild or currently unadapted gene pools in rice to enhance breeding efforts to secure future climate change adaptation. This article is protected by copyright. All rights reserved.
High temperature has a pronounced effect on grain yield and quality in rice. Climate change has increased night temperature more than day temperature in many parts of the world. How rice responds to high night-time temperature (HNT) is largely unknown. This study presents the first effort to assess the response of tropical hybrid rice to HNT. Six commercial tropical hybrid rice cultivars together with a tolerant (N22-aus) and a susceptible (Gharib-indica) genotype were evaluated under control temperature (23 °C) and HNT (29 °C) starting from panicle initiation until maturity under field conditions at the International Rice Research Institute during the dry (DS) and wet (WS) seasons of 2013. Overall, HNT significantly decreased grain yield of Gharib and all tested hybrids across both seasons, with less average reduction in the DS (13.4%) than in the WS (18.6%). Among the yield components, spikelets m−2 most significantly contributed to yield variation under control and/or HNT during both DS and WS followed by grain weight, while the contribution of seed-set was low and season-specific. Grain quality in most hybrids was also strongly affected by HNT, with decreased head rice yield, increased chalkiness and reduced grain width. Given this vulnerability to HNT, there is an urgent need to explore options for improving the adaptation of rice hybrids to increasingly warmer nights.
Understanding how wheat (Triticum aestivum L.) plants under high temperature (HT) regulate lipid composition is critical to developing climate-resilient varieties. We measured 165 glycerolipids and sterol derivatives under optimum and high day and night temperatures in wheat leaves using electrospray ionization-tandem mass spectrometry. Levels of polar lipid fatty acyl chain unsaturation were lower in both heat-tolerant genotype Ventnor and susceptible genotype Karl 92 under HT, compared to optimum temperature. The lower unsaturation was predominantly due to lower levels of 18:3 and higher levels of 18:1 and 16:0 acyl chains. Levels of 18:3-containing triacylglycerols increased 3-fold/more under HT, consistent with their possible role in sequestering fatty acids during membrane lipid remodeling. Phospholipids containing odd-numbered or oxidized acyl chains accumulated in leaves under HT. Sterol glycosides (SG) and 16:0-acylated sterol glycosides (ASG) were higher under HT than optimum temperatures. Ventnor had lower amounts of phospholipids with oxidized acyl chains under HT and higher amounts of SG and 16:0-ASG than Karl 92. Taken together, the data demonstrate that wheat leaf lipid composition is altered by HT, that some lipids are particularly responsive to HT, and that two wheat genotypes, chosen for their differing physiological responses to HT, differ in lipid profile under HT. This article is protected by copyright. All rights reserved.
Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area (GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley, and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9°C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 7 pm and removed at 7 am every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 °C to 17.2 °C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C(-1) ), due to GN reductions (ca. 6% °C(-1) ) linked to a lower number of spikes m(-2) . An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Increasing night temperatures can reduce growth and yield of rice plants, but limited information is available on the comparative effects of high night temperature (HNT) treatment at different growth stages on growth and physiological responses of rice. We conducted a study in controlled-environment chambers to determine the growth and physiological responses and spikelet differentiation of rice cultivars to HNT treatment at different growth stages. Plants were exposed to two temperatures: 30/21 °C (low) and 30/25 °C (high) day/night temperatures. At the end of the vegetative period, plants grown in the low (LNT) and high (HNT) night temperatures were further subdivided and plants were exposed to different temperature treatments in the reproductive growth period. Photosynthesis, night respiration rates, and plant growth parameters were measured at various stages. High night temperature had no significant effects on the growth of rice cultivars during the vegetative phase. Maximum photosynthesis at the vegetative phase was not significantly affected, but plant dark respiration increased (within the 14–20% range). Genotypic variation in dark respiration was observed at later growth stages. Rice plants that received HNT at the early reproductive stage had the lowest number of spikelets per panicle, presenting a 35.9% of degenerated spikelets, significantly higher than those observed in other treatment times. This study shows that the response of rice cultivars to HNT varies with time of treatment and that the occurrence of HNT during the reproductive period provided supportive evidence on how HNT might reduce yield by increasing plant’s dark respiration rate and spikelet degeneration (which consequently reduced sink size), thus, decreasing biomass production.