Effects Of High Temperature Stress Research Articles

Effects of high-temperature stress on gene expression related to photosynthesis in two jujube (Ziziphus jujuba Mill.) varieties

ABSTRACT Elevated temperatures critically impact crop growth, development, and yield, with photosynthesis being the most temperature-sensitive physiological process in plants. This study focused on assessing the photosynthetic response and genetic adaptation of two different heat-resistant jujube varieties ‘Junzao’ (J) and ‘Fucuimi’ (F), to high-temperature stress (42°C Day/30°C Night). Comparative analyses of leaf photosynthetic indices, microstructural changes, and transcriptome sequencing were conducted. Results indicated superior high-temperature adaptability in F, evidenced by alterations in leaf stomatal behavior – particularly in J, where defense cells exhibited significant water loss, shrinkage, and reduced stomatal opening, alongside a marked increase in stomatal density. Through transcriptome sequencing 13,884 differentially expressed genes (DEGs) were identified, significantly enriched in pathways related to plant-pathogen interactions, amino acid biosynthesis, starch and sucrose metabolism, and carbohydrate metabolism. Key findings include the identification of photosynthetic pathway related DEGs and HSFA1s as central regulators of thermal morphogenesis and heat stress response. Revealing their upregulation in F and downregulation in J. The results indicate that these genes play a crucial role in improving heat tolerance in F. This study unveils critical photosynthetic genes involved in heat stress, providing a theoretical foundation for comprehending the molecular mechanisms underlying jujube heat tolerance.

Gills de novo assembly reveals oxidative stress, unfolded protein, and immune response on red cusk-eel (Genypterus chilensis) under thermal stress

The heat waves on the South Pacific coast could lead to thermal stress in native fish. The red cusk-eel (Genypterus chilensis) is relevant for Chilean artisanal fisheries and aquaculture diversification. This study examined the effect of high-temperature stress in the gills of G. chilensis in control (14 °C) and high-temperature stress (19 °C) conditions. High-temperature stress induces a significant increase in gills cortisol levels. Additionally, oxidative damage was observed in gills (protein carbonylation and lipoperoxidation). RNA-seq data was used to build the first transcriptome assembly of gills in this species (23,656 annotated transcripts). A total of 1138 down-regulated and 1531 up-regulated transcripts were observed in response to high-temperature stress in gills. The enrichment analysis showed immune response and replication enriched processes (on down-regulated transcripts), and processes related to the folding of proteins, endoplasmic reticulum, and transporter activity (on up-regulated transcripts). The present study showed how gills could be affected by high-temperature stress.

Effect of High Temperature Stress on Photosynthetic Pigments, Dry Matter Partitioning and Yield of Blackgram (Vigna mungo L.) Genotypes at Pod Formation Stage

A field experiment was conducted at College farm, Agricultural College, Bapatla, Acharya N.G. Ranga Agricultural University during summer, 2022 and 2023 to study the impact of high temperature stress on photosynthetic pigments, dry matter partitioning and yield of blackgram genotypes at pod formation stage. The experiment was carried out in randomized block design with two replications. Among the thirty blackgram genotypes screened for their tolerance to high temperature stress at pod formation stage, the genotype, TBG-129, LBG-1015 and PU-1804 were found to withstand high temperature stress and maintain higher total chlorophyll content, carotenoids content, dry matter partitioning and higher seed yield per plant indicating tolerance to high temperature stress. These blackgram genotypes can be further used as donors in the pulse breeding program for development of heat resilent varieties.

Effect of high temperature stress on metabolome and aroma in rice grains

Heat stress poses a significant challenge to global rice production, affecting yield and grain quality. Elevated temperatures during the flowering and grain-filling stages, both day and night, lead to reduced yield and compromised grain quality. This impact is more pronounced during nighttime high-temperature stress, seriously threatening rice productivity. With global temperatures rising, there is a looming threat to rice production. Aromatic rice, prized for superior aroma and grain quality, is particularly vulnerable to heat. Therefore, the present work has been carried out to investigate how high temperature affects the aromatic metabolites in rice grains among the 15 rice genotypes (fourteen aromatic and one non-aromatic rice i.e., Nagina 22). Results from the present study indicated that the inactive (mutated) BADH2 gene expression was down-regulated under high-temperature stress conditions and no 2-acetyl-1-pyrroline (2-AP) accumulation was detected in the selected rice genotypes. However, the increase in levels of L-proline (precursor molecule for 2-AP) was detected, and due to the down-regulation of inactive BADH2, the oxidation of L-proline into 2-AP was affected. Proline amino acid significantly increased under high temperatures, impacting aroma quality. Metabolome studies revealed variations in compound detection among scented rice genotypes. Understanding these metabolites aids in addressing the loss of aroma in fragrant rice genotypes, offering insights into developing stable aromatic rice varieties under elevated temperature conditions. The study aims to identify metabolites causing aroma loss in aromatic rice. Results will aid in understanding aroma depletion mechanisms in scented rice under high-temperature stress, guiding the development of a stable aromatic rice variety in elevated temperatures.

Elevated CO2 ameliorates the high temperature stress effects on physio-biochemical, growth, yield traits of maize hybrids

The rising temperatures and levels of carbon dioxide in the atmosphere are anticipated to have a significant impact on the productivity of agricultural crops. Although, the individual effects of elevated CO2 and temperature have been extensively studied in C3 and C4 crops, there remains a scarcity of research investigating their interactive effects specifically on maize hybrids. The impact of elevated temperature and its interaction with elevated CO2 on phenology, physiology, biomass, and grain yield of maize hybrids was assessed in a field experiment using Free Air Temperature Elevation (FATE) facility. The results showed that elevated temperature (eT) increased the anthesis silking interval (ASI), while the presence of elevated CO2 along with elevated temperature (eT + eCO2) mitigated this effect. The differential expression were observed between hybrids depending on their genetic potential. Furthermore, the net photosynthetic rate (Anet), stomatal conductance (gs), and transpiration rate (Tr) of hybrids decreased under elevated temperature but eT + eCO2 condition helped in reverting its impact to some extent. In term of leaf composition, the highest level of total soluble sugars (TSS) and starch was observed under eT + eCO2 conditions, possibly due to improved Anet in the presence of elevated eCO2. The negative impact of eT was also evident through increased proline and MDA content, but eT + eCO2 ameliorated the adverse effect of eT. The biomass and grain yield also responded similarly, among the hybrids 900M GOLD recorded superior performance for grain yield at eT condition exceeding 35 °C. On the other hand, DHM117 experienced a significant reduction in grain yield under eT, but performed better under eT + eCO2 due to its improved physiological response to eCO2. The study indicated that elevated levels of carbon dioxide can actually mitigate the detrimental effects of elevated temperature on maize crop. This positive impact on maize crop can be attributed to an enhanced physiological performance in the presence of eCO2 which enables the plants to maintain satisfactory yield levels despite the challenging environmental conditions.

Alleviating the Effects of High-Temperature Stress on Parsley Plants by Foliar Application of Proline, Glycine Betaine, and Salicylic Acid

Alleviating the Effects of High-Temperature Stress on Parsley Plants by Foliar Application of Proline, Glycine Betaine, and Salicylic Acid

Response Mechanisms of Woody Plants to High-Temperature Stress.

High-temperature stress is the main environmental stress that restricts the growth and development of woody plants, and the growth and development of woody plants are affected by high-temperature stress. The influence of high temperature on woody plants varies with the degree and duration of the high temperature and the species of woody plants. Woody plants have the mechanism of adapting to high temperature, and the mechanism for activating tolerance in woody plants mainly counteracts the biochemical and physiological changes induced by stress by regulating osmotic adjustment substances, antioxidant enzyme activities and transcription control factors. Under high-temperature stress, woody plants ability to perceive high-temperature stimuli and initiate the appropriate physiological, biochemical and genomic changes is the key to determining the survival of woody plants. The gene expression induced by high-temperature stress also greatly improves tolerance. Changes in the morphological structure, physiology, biochemistry and genomics of woody plants are usually used as indicators of high-temperature tolerance. In this paper, the effects of high-temperature stress on seed germination, plant morphology and anatomical structure characteristics, physiological and biochemical indicators, genomics and other aspects of woody plants are reviewed, which provides a reference for the study of the heat-tolerance mechanism of woody plants.

High temperature stress induced oxidative stress, gut inflammation and disordered metabolome and microbiome in tsinling lenok trout

Tsinling lenok trout (Brachymystax lenok tsinlingensis Li) is a species of cold-water salmon that faces serious challenges due to global warming. High temperature stress has been found to damage the gut integrity of cold-water fish, impacting their growth and immunity. However, limited research exists on the causal relationship between gut microbial disturbance and metabolic dysfunction in cold-water fish induced by high temperature stress. To address this gap, we conducted a study to investigate the effects of high temperature stress (24 °C) on the gut tissue structure, antioxidant capacity, gut microorganisms, and metabolome reactions of tsinling lenok trout. Our analysis using 16 S rDNA gene sequencing revealed significant changes in the gut microbial composition and metabolic profile. Specifically, the abundance of Firmicutes and Gemmatimonadetes decreased significantly with increasing temperature, while the abundance of Bacteroidetes increased significantly. Metabolic analysis revealed a significant decrease in the abundance of glutathione, which is synthesized from glutamate and glycine, under high temperature stress. Additionally, there was a notable reduction in the levels of adenosine, inosine, xanthine, guanosine, and deoxyguanosine, which are essential for DNA/RNA synthesis. Conversely, there was a significant increase in the abundance of D-glucose 6 P. Furthermore, high temperature stress adversely affects intestinal structure and barrier function. Our findings provide valuable insights into the mechanism of high temperature stress in cold-water fish and serve as a foundation for future research aimed at mitigating the decline in production performance caused by such stress.

Negative effects of high-temperature stress on gametophyte performance and their consequences for seed reproduction in wild plants

(1) Plant regeneration by seeds is highly sensitive to temperature stress, particularly in the gametophyte stage. However, most of the existing research has focused on one single stage of gametophyte development and/or conducted using cultivated or a very few model species. Thus, it is unclear whether the results of such studies can be applied to natural populations. (2) To fill this gap, we investigated a) the effects of chronic heat stress (CHS; 17 days) at 35/30 °C (moderate stress) and 40/35 °C (severe stress) on gametophyte performance, and b) how these effects translated into seed quantity and quality. We measured six traits related to male (anther length, pollen production and size) and female (ovary length, ovule production, and size) gametophyte performance and leaf chlorophyll fluorescence (Fv/Fm) in four wild Silene species. The ripe seeds of the treated plants were used to measure seed mass and seed production; the seed germination was characterized in terms of germination percentage, speed, and synchrony. (3) Fv/Fm decreased significantly in both heat treatments, confirming a negative effect of CHS on overall plant performance. All male gametophyte traits decreased significantly in both CHS treatments compared to the control. The length and size of the ovary were significantly smaller in the 40/35 °C treatment than in the 35/30 °C treatment and the control, while ovule production decreased significantly in both CHS treatments compared to the control. The negative effects on gametophyte performance translated into significantly fewer seeds in the 35/30 °C and 40/35 °C treatments compared to the control. CHS treatments did not affect the seed mass. The final germination percentage differed weakly significantly between the severe treatment and the control but did not show any negative impacts by heat stress, whereas seed germination was significantly faster in the treated plants, both moderate and severe. Germination synchrony was not affected by heat treatments. (4) The high sensitivity of gametophytes in vascular plants to high-temperature stress implies that climate change-associated heat waves can significantly impact seed reproduction in wild plants. The altered seed quantity could have potential consequences for the long-term survival of the wild plant populations and the performance of the granivores.

Resistance index and browning mechanism of apple peel under high temperature stress

Apples are one of the most important economic crops worldwide. Because of global warming and an aggravation of environmental, abnormally high temperatures occur frequently in fruit-growing season and seriously affect normal fruit growth and reduce fruit quality and yield. We took five-year-old ‘Ruixue’ (Qinfu 1 × Pink Lady; CNA20151469.1) fruits as test materials, and the ambient temperature during fruit development was monitored. The results showed that during the fruit-growing season, especially during the rapid growth stage (July to August), the maximum daily temperature exceeded 30 °C and lasted for more than 40 days. To determine the effects of high temperature stress on the apple fruit resistance, we treated expanding, veraison, and maturity-period fruits at different temperatures. It was found that the fruits of the expanding period showed strong resistance to high temperature stress, whereas during veraison and maturity, fruit resistance to high temperature stress decreased, and the fruit peel browning phenotype appeared. Meanwhile, the content of malonaldehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2.-) in the peel gradually increased with increasing temperature. The content of total phenols, flavanol, and flavonoids in the peel decreased substantially at 45 °C. Moreover, it was found that polyphenol oxidase gene (MdPPO1) was most sensitive to high temperature stress in apple. Furthermore, transient and stable MdPPO1 overexpression significantly promoted peel browning. The transgenic materials were more sensitive to high temperatures, and browning was more severe compared to non-genetically modified organism (WT). Stable MdPPO1 knockout calli obtained via clustered regularly interspersed short palindromic repeats (CRISPR/Cas9) gene knockout technology reduced the browning phenotype, and the resultant fruits were not sensitive to the effects of high temperature stress. Thus, MdPPO1 expression may be a key factor of high temperature–related changes observed in the browning phenotype that provides a scientific theoretical basis for the selection of high temperature–resistant varieties and apple cultivation and management in the future.

Effects of High Temperature Stress on the Physiological and Biochemical Characteristics of Paeonia ostii.

In order to explore the effects of high temperature stress on the physiological characteristics of Paeonia ostii, the Paeonia ostii were subjected to 25 °C, 35 °C, 38 °C, and 40 °C for 7 days. Meanwhile, the physiological indicators of oxidative stress (hydrogen peroxide, H2O2; malondialdehyde, MDA; relative electrical conductivity, REC), antioxidant enzyme activity (superoxide dismutase, SOD; ascorbate peroxidase, APX; catalase, CAT; peroxidase, POD), photosynthetic pigment content (chlorophyll a, Chla; chlorophyll b, Chlb), photosynthetic characteristics (net photosynthetic rate, Pn; intercellular CO2 concentration, Ci; stomatal conductance, Gs; transpiration rate, Tr), and osmoregulatory substances content (soluble protein, SP; soluble sugar, SS) were determined. The results showed that, with the increase in temperature and stress time, the H2O2 content, MDA content, REC value, CAT activity, and APX activity increased, while Chla content, Chlb content, SS content, and SP content decreased. With the extension of stress time, the SOD activity, POD activity, and Tr value of each high temperature stress group first increased and then decreased; Ci first decreased, then increased, and then decreased; meanwhile, Pn and Gs showed an overall downward trend. PLS-DA (partial least squares discriminant analysis) was used to analyze the changes in physiological and biochemical indexes of peony leaves under 40 °C stress for different days. SOD was found to be the biggest factor affecting the changes in physiological and biochemical indexes of peony leaves treated with different days of stress.

Effect of high temperature stress on glycogen metabolism in gills of Yesso scallop Patinopecten yessoensis.

Glycogen is the main energy storage material in mollusc, and the regulation of its metabolism is essential for the response against high temperature stress. In the present study, the alternation of lactic acid (LD) content, glycogen reserves, mRNA expression level of genes encoding glycogen metabolism enzymes and activities of glycogen metabolism enzymes in gills of Yesso scallop Patinopecten yessoensis after an acute high temperature treatment at 25°C were examined to understand the effect of high temperature on glycogen metabolism. The activity of T-ATPase in gills of scallops presented a gradual increase trend especially at 6h after the acute high temperature treatment (p<0.05). The glycogen reserves did not change significantly even there was a downward trend at 24h after the acute high temperature treatment (p>0.05). The mRNA transcripts of glycogen synthase (PyGCS) in gills of scallops decreased significantly at 1, 3, 6 and 12h (p<0.05), and recovered to normal level at 24h (p>0.05) after the acute high temperature treatment, while that of glycogen phosphorylase a (PyGPa) and phosphoenol pyruvate carboxy kinase (PyPEPCK) were both significantly down-regulated from 1h to 24h (p<0.05) after the acute high temperature treatment. The activity of PyGPa at 1, 12 and 24h and the content of LD at 3 and 24h in gills of scallops after the acute high temperature treatment both increased significantly (p<0.05). Furthermore, the mRNA transcripts of hexokinase (PyHK) and pyruvate kinase (PyPK) in gills of scallops increased significantly (p<0.05) after the acute high temperature treatment, and the response of PyHK was stronger. However, there was no significant difference on the activity of PyPK in gills of scallops between the experimental samples and the blank samples (p>0.05). In addition, the mRNA transcripts of citrate synthase (PyCS) in gills of scallops were significantly down-regulated at 6h and 12h (p<0.05), and finally returned to normal level at 24h (p>0.05) after the acute high temperature treatment. These results collectively indicated acute high temperature stress leaded the alternation of glycogen metabolism in the gills of Yesso scallop, glycogenesis, gluconeogenesis and TCA cycle were inhibited, and the glycolysis pathway of glycogen was enhanced to produce more energy for coping with environmental pressure.

Investigation of generative high temperature tolerances of some cotton (Gossypium hirsutum L.) varieties

The potential of cotton genotypes to form buds, flowers and bolls is not sufficient to achieve cotton seed yield targets. Despite global warming buds, flowers and bolls that mature in cotton plants must be successfully transformed into products. However, this is related to the generative tolerance of the genotype to high temperature. In study aims to scan the negative effects of high temperature stress on the generative development on cotton varieties registered in Turkey in the last 10 years. The experiment was established in the GAP International Agricultural Research and Training Center trial field in 2020, with 4 blocks according to the Augmented design. Six standards (Tamcot Spnhix, SJU86, AGC208, ST468, ST474, Carmen) and 88 cotton varieties registered in Turkey National Variety List were used as trial material. In this study, high temperature pollen vitality stress index (HTPVSI) and high temperature shedding stress index (HTSSI) properties were investigated. According to the results of the experiments we conducted, it was determined that the HTPVSI values ranged between 0.17-1.26, the HTPVSI averages of the standards were 1.17, and the HTPVSI averages of the genotypes were 0.99. It has been determined that HTSSI values vary between 0.30-1.71. It was determined that the mean HTSSI values of the standards were 0.89 and the genotypes were 1.00. It was determined that there was a wide variation among the genotypes screened for generatively high temperature stress. Using HTSSI and HTPVSI features is recommended as a selection criterion since it is an important trait for screening genotypes in terms of tolerance or sensitivity to generative high temperature stress in cotton plants. In our study, the results were not similar to each other in terms of HTPVSI and HTSSI traits, due to the low share of flower shedding after applying HTSP (High Temperature Shock Practice: 96 hours of uninterrupted exposure to high temperature during generative periods) in the shedding rate. When the examined HTSSI and HTPVSI traits were examined together, no cotton genotypes were found to be generatively tolerant. In terms of sensitivity of genotypes to high temperature, 18 cotton genotypes were found in the medium tolerant group and 25 cotton genotypes were found in the sensitive group.

Effect of high-temperature stress on rice grain quality

High-temperature stress (HS) due to global warming has become a serious threat to global food and nutritional security. Among the various agro-morphological and physiological changes observed in rice (Oryza Sativa L.) due to high-temperature sress, yield and grain quality are highly important and they vary among the germplasm. As reports on the effect of high-temperature stress on grain quality are less, rice grown under ambient as well as high-temperature conditions were subjected to important grain quality aspects to identify the least affected rice. Twenty-five entries were cultivated in two neighboring experimental plots, one for normal and the other for high-temperature stress (HS). High-temperature stress was imposed by enclosing the field-grown crop with a transparent polyethylene sheet supported by a metal frame at the onset of the reproductive phase. Temperature inside the above structure (treatment) as well as outside (control) was recorded until the crop was harvested. The mean minimum and maximum increase in temperatures were 0.67°C and 10.2°C respectively over the ambient conditions. After harvesting, all the paddy samples of both control and treatment were dried under shade and processed to brown rice which was manually separated into chalky and normal grains on a trans-illuminator. Further, total starch and protein contents were estimated separately in the chalky and normal grains of each sample. ANOVA indicated that temperature during the reproductive stage significantly (p&lt;0.01) influenced the starch as well as protein contents. An increase in total starch content was observed in both normal and chalky grains under high-temperature stress. The difference in total starch amongst the genotypes was significant (p&lt;0.01), however, the differences in total starch content between normal and chalky grain under both control and high-temperature stress condition was non-significant. Although the mean protein content for all the genotypes was not significantly affected in chalky and normal grains under control, it was reduced by &gt;5% in chalky grains under high-temperature stress. Five entries noted £10% yield loss. Of these, IET29944 appears to be less affected in multiple parameters.

Investigation of Vegetative High Temperature Tolerance of Some Cotton (Gossypium hirsutum L.) Varieties

Our aims to scan the harmful effects of high temperature stress on vegetative development on cotton varieties registered in our country. The experiment was established in the GAPUTAEM trial area in 2020, with 4 blocks according to the Augmented design. Six standards (Tamcot Spnhix, SJU86, AGC208, STV468, ST474, Carmen) and 88 cotton varieties registered in the national variety list were used as trial material. In this study, relative cell injury rate (RCI) and leaf high temperature stress index values (LHTSI) were investigated. Our investigation results show cell membrane damage (%RCI) varied between 41.81% and 74.84%. While the average of the standards used in the experiment was 68.15%, the overall average was found to be 62.42%. Leaf high temperature stress index (LHTSI) values varied between 0.48 and 1.85, while the LHTSI average of the standards was 0.98, and the overall LHTSI average of the experiment was found to be 1.02. It was determined that there was a wide variation among the genotypes screened for vegetatively high temperature stress. Using LHTSI and RCI features, it has been concluded that it is an important, effective, easy, and applicable selection criterion for screening genotypes regarding tolerance or sensitivity to high temperature stress vegetatively in cotton plants. Applying these two parameters together is recommended to obtain more accurate results. It was determined that only the Teksa415 cotton variety was vegetatively tolerant. Vegetatively, 31 cotton genotypes were found in the medium tolerant group and 62 cotton genotypes in the sensitive group.

Effects of high-temperature stress on crop plants

High-temperature stress is leading abiotic stress that restricts plant growth, development and yield globally. It reduces plants' productivity, affecting their morphological, physiological, phenological, biochemical and molecular reactions. Major effects of heat stress include impaired membrane systems, denaturation of proteins, enzyme inactivation etc. Responses of plants towards high-temperature stress vary from species to species, with duration and degree of the stress. Plant scientists' main goal is to develop various techniques/practices for satisfying enhanced crop yields and quality. In the cropping system, legumes grains have a significant role in promising food security to the increasing world population. However, legumes are susceptible to several abiotic stresses and heat stress has been known as a primary constraint in limiting their production. Also, the quantity and quality of seed storage proteins are negatively affected by high-temperature stress. Therefore, new approaches to improve legume heat tolerance are critical for reducing yield losses. Plants have several mechanisms for high-temperature stress such as enzymatic and non-enzymatic antioxidant systems, ion transporter and heat shock proteins activated to cope with stress-induced alterations. This review highlights the current research on various responses of plants to heat stress and plant thermo-tolerance mechanisms at the molecular level and illustrates the role of different exogenous molecules in alleviating the heat-induced damages and transgenic methods used to improve plants' tolerance to high temperatures.

Effects of Post-Anthesis High-Temperature Stress on Carbon Partitioning and Starch Biosynthesis in a Spring Wheat (Triticum aestivum L.) Adapted to Moderate Growth Temperatures.

This study investigates carbon partitioning in the developing endosperm of a European variety of spring wheat subjected to moderately elevated daytime temperatures (27°C/16°C d/night) from anthesis to grain maturity. Elevated daytime temperatures caused significant reductions in both fresh and dry weights and reduced the starch content of harvested grains compared to plants grown under a 20°C/16°C d/night regimen. Accelerated grain development caused by elevated temperatures was accounted for by representing plant development as thermal time (°C DPA). We examined the effects of high-temperature stress (HTS) on the uptake and partitioning of [U-14C]-sucrose supplied to isolated endosperms. HTS caused reduced sucrose uptake into developing endosperms from the second major grain-filling stage (approximately 260°C DPA) up to maturity. Enzymes involved in sucrose metabolism were unaffected by HTS, whereas key enzyme activities involved in endosperm starch deposition such as ADP-glucose pyrophosphorylase and soluble isoforms of starch synthase were sensitive to HTS throughout grain development. HTS caused a decrease in other major carbon sinks such as evolved CO2, ethanol-soluble material, cell walls and protein. Despite reductions in the labeling of carbon pools caused by HTS, the relative proportions of sucrose taken up by endosperm cells allocated to each cellular pool remain unchanged, except for evolved CO2, which increased under HTS and may reflect enhanced respiratory activity. The results of this study show that moderate temperature increases can cause significant yield reductions in some temperate wheat cultivars chiefly through three effects: reduced sucrose uptake by the endosperm, reduced starch synthesis and increased partitioning of carbon into evolved CO2.

Wheat cultivar mixtures increase grain yield under varied climate conditions

Scaling current cereal production to meet the globally increasing food demand will be a challenge under climate change. Previous studies have shown that crop diversification, such as intercropping, can increase crop yield, stability, resource-use efficiency and resistance to both biotic and abiotic stresses in agroecosystems. However, more evidence is needed to explain the influence of inter-annual climate variations on crop yield in the context of genetic diversity. Here, we conducted a field experiment over four years in the North China Plain to test the effect of genetic diversity on yield under varied climate conditions. We compared the performance of eight winter wheat cultivars in monocropping with that of mixed cropping of two (mixture-2), four (mixture-4), and eight (mixture-8) cultivars. Our results showed that the yields of all cultivar mixtures were higher than those of their component cultivars in monocropping from 2017 to 2020. In particular, the grain yields of mixture-4 and mixture-8 were significantly increased by 7.37% and 5.94% in the drier years (2017 and 2019), compared with that of the highest yield of local cultivar (LY502). From 2017 to 2020, yield components in wheat mixed cropping had synergetic effects that could offset the tradeoffs among them and obtained an optimized combination at population level. Moreover, the yield stability of all mixtures was higher than the weighted means of monocultures averaged across the four years. The cultivation of mixtures of wheat cultivars effectively alleviated the negative effect of high temperature stress on 1000-grain weight, and improved grain water use efficiency in the drier years. Our findings showed that enhancing wheat genetic diversity at population level can effectively promote grain yield under drought and high temperature, which can be considered as an ecological approach to cope with global climate change towards food security.

Orthosilicic acid and Seaweed Extract Alleviate the Deteriorative Effects of High Temperature Stress in Brassica juncea (L.) Czern &amp; Coss.

Orthosilicic acid and Seaweed Extract Alleviate the Deteriorative Effects of High Temperature Stress in Brassica juncea (L.) Czern &amp; Coss.

Study on Heat Resistance of Peony Using Photosynthetic Indexes and Rapid Fluorescence Kinetics

To investigate the effects of high-temperature stress on the chlorophyll fluorescence induction kinetics of peony and to determine indicators for the rapid screening of varieties responding to high temperatures, three four-year-old peony variety, ‘Fengdanbai’, ‘Huhong’, and ‘Yinhongqiaodui’, were selected as materials. The photosynthetic curves (Pn-PAR) and fast chlorophyll fluorescence curves (OJIP curves) of peony leaves were measured at different times under high-temperature stress conditions (40 °C), the changes in the photosynthetic characteristics of different peony varieties under high-temperature stress were analyzed, and the heat tolerance of peony was evaluated. The results showed that ‘Huhong’ grew well within 16 days, while all of the other varieties showed obvious wilting at 6–9 days. High temperatures damaged the structure and function of the photosystem of peony leaves, indicating that the maximum net photosynthetic rate (Pnmax), apparent quantum efficiency (AQE), maximum photochemical efficiency (Fv/Fm), and photosynthetic performance index (PIABS) all tended to decrease under high-temperature stress, while the rate of closing the PS II reaction center (Mo) and the absorption per reaction center (ABS/RC), the capture (TRo/RC), and the dissipation (Dio/RC) of light energy per reaction center showed an overall increasing trend. The ability to cope with high-temperature stress differed among varieties, and the heat tolerance was determined to be in the descending order of ‘Fengdanbai’ &lt; ‘Yinhongqiaodui’ &lt; ‘Huhong’. The correlation analysis among the parameters and the analysis of the morphological change patterns in peony leaves concluded that PIABS, Dio/RC, and Mo could be used as indicators of peony tolerance to high-temperature stress. The results of the study can provide a basis for the screening of heat-tolerant peony species and peony heat defense in the Jiangnan area.