Effects Of High Temperature Stress Research Articles

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 & Coss.

Orthosilicic acid and Seaweed Extract Alleviate the Deteriorative Effects of High Temperature Stress in Brassica juncea (L.) Czern & 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’ < ‘Yinhongqiaodui’ < ‘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.

Strategies for indica rice adapted to high-temperature stress in the middle and lower reaches of the Yangtze River.

High temperatures caused by climate warming severely affect the grain yield and quality of rice. In this study, the rice cultivars Longliangyou Huazhan (LLYHZ) and Quanliangyou 2118 (QLY2118) were selected as the experimental materials for investigation of an optimal cultivation system under high-temperature treatment. In addition, the heat-resistant cultivar Huanghuazhan (HHZ) and heat-sensitive cultivar Huiliangyou 858 (HLY858) were chosen as the experimental materials to study the effects of exogenous plant growth regulators on heat stress responses under high-temperature treatment. The results showed that mechanical transplanting of carpet seedlings and delayed sowing effectively increased the leaf area index and reduced the canopy temperature of LLYHZ and QLY2118. Furthermore, carpet seedling mechanical transplantation and delayed sowing improved grain yield and quality. Spray application of five plant growth regulators revealed that brassinolide and salicylic acid had the strongest effects on significantly improving antioxidant enzyme activities in the panicle, which would reduce the damage caused by the accumulation of reactive oxygen species and enhance plant tolerance of high-temperature stress. In addition, brassinolide and salicylic acid enhanced the percentage of anther dehiscence and percentage seed set. In this study, a set of simplified eco-friendly cultivation techniques for single-season indica rice adaptation to high-temperature stress was established. These results will be of great importance in alleviating the effects of high-temperature stress on rice production.

Increased abundances of potential pathogenic bacteria and expressions of inflammatory cytokines in the intestine of oyster Crassostrea gigas after high temperature stress

High temperature stress is a significant threat to the health of oysters, but the effects on their intestinal performances are not well understood. In this study, the effects of high temperature stress on the intestinal histology, immune response and associated microbiota were investigated in Crassostrea gigas after rearing at 20, 25 and 28 °C for 21 days. With the increase of temperature, shortened and shed microvilli as well as increased goblet cells were observed in the intestines of oysters. The transcripts of cytokines CgIL17-5, CgTNF-2 and CgTGF-β and apoptosis-related gene CgCaspase-3 in intestine increased with the increasing temperature. Further, the diversity and composition of the oyster intestinal microbiota changed after high temperature stress. The 16S rRNA gene copy number per ng of DNA in the T25 (5.16 × 105) and T28 (1.63 × 105) groups were higher than that in the control group (8.62 × 104). The Chao 1 index in the T25 (238.00) and T28 (240.17) groups was lower than that in the control group (279.00). The Shannon index decreased progressively with the increasing temperature, with the value in the T28 group (4.44) significantly lower than that in the control group (5.40) (p < 0.05). The abundances of potential pathogenic bacteria such as Acinetobacter, Pseudomonas, Vibrio and Endozoicomonas increased while that of probiotic bacteria Bacillus decreased after high temperature exposure. Functional prediction indicated that the pathways associated with bacterial proliferation were enriched at 25 °C, while those involved in protein synthesis were blocked at 28 °C. Collectively, these results suggested that high temperature stress led to an increased abundances of potential pathogenic bacteria and expressions of inflammatory cytokines in the intestine, which may consequently affect the functional integrity of the intestinal barrier in oysters.

Reduction of High-Temperature Damage on Paeonia ostii through Intercropping with Carya illinoinensis

Paeonia ostii is an emerging woody oil crop, but the high temperature in summer is extremely unfavorable for its growth and development. Understory intercropping cultivation would provide shaded environments which could effectively reduce the ambient temperature. In order to explore whether understory intercropping cultivation would reduce the effects of high-temperature stress on P. ostii, the changes of leaf physiological indicators and leaf microstructures of sole-cropping and intercropping P. ostii were investigated. P. ostii that intercropping cultivated under Illinois pecans (Carya illinoinensis (Wangenh.) K. Koch) with 4 m × 4 m and 4 m × 8 m rowing spaces were used as samples in this study. The results showed that with continuous high temperature, the high-temperature damage index of P. ostii kept increasing, whereas the leaf relative water content continued to decline. Compared to sole-cropping, the high-temperature damage index, relative electrical conductivity, proline content, antioxidant enzymes superoxide dismutase (SOD), and ascorbate peroxidase (APX) activities of intercropping P. ostii under C. illinoinensis were significantly decreased, whereas the leaf relative water content was higher. Moreover, compared to sole-cropping, intercropping P. ostii under C. illinoinensis increased SPAD and chlorophyll contents, made mesophyll cell ultrastructures more intact, and made the chloroplasts rounder and more filled with starch granules and lipid globules, leading to enhanced photosynthesis (Pn) and transpiration rates (Tr). Notably, the reduction of high-temperature damage on intercropping P. ostii under C. illinoinensis with 4 m × 4 m rowing spaces was more significant than that under C. illinoinensis with 4 m × 8 m rowing spaces. This research provides some reference values for efficient plantation of P. ostii in the middle and lower reaches of the Yangtze River in China.

Individual and Combined Effects of High-Temperature Stress at Booting and Flowering Stages on Rice Grain Yield

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

Larval Thermal Tolerance of Kellet's Whelk (Kelletia kelletii) as a Window into the Resilience of a Wild Shellfishery to Marine Heatwaves

Marine heatwave (MHW) events are emerging as dominant and disruptive extreme disturbance events on the Pacific coast. These events are expected to have significant impacts on shellfish species and aquaculture operations. In general, thermal stress induced by MHW events has been documented to have impacts on the productivity and biodiversity of coastal marine ecosystems in California. Yet, there is limited understanding on how thermal stress will affect economically important shellfish species, especially at vulnerable early life stages. This study assessed the effect of high temperature stress that resembled recent local MHW conditions on the larval stages of the Kellet's whelk, Kelletia kelletii, an emerging seafood species from California temperate reefs. Adult whelks were collected at temperate reef sites in the Santa Barbara Channel, and larvae were sourced from egg capsules laid by adult whelks in the laboratory. Thermotolerance trials were determined for two stages of K. kelletii larvae: encapsulated veligers and veligers that had emerged from the capsules as hatchlings. During the trials, larvae were scored for two metrics: (1) mortality and (2) developmental abnormality. After exposure of larvae to a range of temperatures (15°C–37°C) in acute thermotolerance trials (1 h), the mortality of veligers and hatchlings occurred at similar temperatures. In contrast, temperatures that induced developmental abnormalities for both encapsulated veligers and hatchlings were lower than temperatures that caused mortality. And further, temperatures that induced abnormal development were different for the two stages. These results provide some of the first insights on effects of environmentally relevant MHW temperatures on larval forms of the Kellet's whelk, and suggest the potential decline of populations in situ in response to continued stress from local MHW events.

Characterization of Gut Microbiome in the Mud Snail Cipangopaludina cathayensis in Response to High-Temperature Stress.

Simple SummaryThis study investigated the effects of high-temperature stress on the intestinal microbiome of Cipangopaludina cathayensis. High-temperature exposure significantly changed the intestinal microbiota structure of C. cathayensis. The relative abundance of putatively beneficial bacteria decreased, whereas the relative abundance of putatively pathogenic bacteria increased after thermal stress. Consistent with the trends of change in the intestinal microbiota, the high-temperature treatment inhibited some carbohydrate metabolism pathways and induced certain disease-related pathways. Thermal stress disrupts the homeostasis of gut microbiota, which may lead to disease outbreak in C. cathayensis.The mud snail Cipangopaludina cathayensis is a widely distributed species in China. Particularly in Guangxi province, mud snail farming contributes significantly to the economic development. However, global warming in recent decades poses a serious threat to global aquaculture production. The rising water temperature is harmful to aquatic animals. The present study explored the effects of high temperature on the intestinal microbiota of C. cathayensis. Snail intestinal samples were collected from the control and high-temperature groups on days 3 and 7 to determine the gut microbiota composition and diversity. Gut bacterial community composition was investigated using high-throughput sequencing of the V3–V4 region of bacterial 16S rRNA genes. Our results suggested that thermal stress altered the gut microbiome structure of C. cathayensis. At the phylum level, Proteobacteria, Bacteroidetes, and Firmicutes were dominant in C. cathayensis gut microbiota. The T2 treatment (32 ± 1 °C, day 7) significantly decreased the relative abundance of Firmicutes, Actinobacteria, and Deinococcus-Thermus. In T2, the abundance of several genera of putatively beneficial bacteria (Pseudomonas, Aeromonas, Rhodobacter, and Bacteroides) decreased, whereas the abundance of Halomonas—a pathogenic bacterial genus—increased. The functional prediction results indicated that T2 treatment inhibited some carbohydrate metabolism pathways and induced certain disease-related pathways (e.g., those related to systemic lupus erythematosus, Vibrio cholerae infection, hypertrophic cardiomyopathy, and shigellosis). Thus, high temperature profoundly affected the community structure and function of C. cathayensis gut microbiota. The results provide insights into the mechanisms associated with response of C. cathayensis intestinal microbiota to global warming.

Effects of high-temperature stress on photosynthesis of a new variety "SF-2" in Neoporphyra haitanensis

Effects of high-temperature stress on photosynthesis of a new variety "SF-2" in Neoporphyra haitanensis

Effect of long-term temperature stress on the intestinal microbiome of an invasive snail.

The gut microbiome is vital to the physiological and biochemical functions of the host, and changes in the composition of these microbial communities may affect growth and adaptability to the environment. Pomacea canaliculata is an invasive freshwater snail which has become a serious agricultural pest. Temperature adaptation is considered an important reason for the widespread distribution of this species. To date, the contribution of the gut microbes to host fitness of P. canaliculata during long-term temperature stress is not well understood. In this study, the morphological changes and intestinal microbiome of P. canaliculata under long-term stress at low temperature (15°C) and high temperature (35°C) were investigated with laboratory experiments. Compared with control group (25°C), the alpha diversity increased and pathogenic bacteria enriched changed under high and low temperature stress. The effect of high temperature stress on the intestinal microbiome of P. canaliculata was more significant than that of low temperature stress. A sustained high temperature environment led to an increase in the abundance of pathogenic bacteria, such as Aeromonas and Enterobacter, and a decrease in the abundance of immune-related bacteria such as Bacteroidetes, Firmicutes, and Lactococcus. These intestine microbiome changes can increase the risk of diseases like intestinal inflammation, and lead to more deaths at high temperature environments. In addition, with the extension of stress time from 14 to 28 days, the beneficial bacteria such as Bacteroidetes, Firmicutes, and Lactococcus were significantly enriched, while potential pathogenic bacteria such as Pseudomonas, Acinetobacter, Shivalella, and Flavobacterium decreased, suggesting that intestinal microbiota may play an important role in host response to heat stress. These results are consistent with previously reported results that the survival rate of both male and female P. canaliculata no longer significantly reduced after 21 days of high temperature stress, suggesting that the surviving P. canaliculata had gradually adapted to high temperature environments under long-term high temperature stress.

Identification of heat-tolerant rice genotypes and their molecular characterisation using SSR markers

The effect of high-temperature stress has a critical impact in causing reduced crop yield. The focus of the current investigation is the identification of heat-tolerant rice varieties that can alleviate the effects of stress. Among the ten genotypes evaluated across various parameters such as leaf area, dry weight, photosynthetic rate, stomatal conductance and spikelet fertility, N-22 showed superior characteristics for the grain filling parameters along with CR-Dhan 307. The variety CR-Dhan 307 with significantly higher mean pollen viability (80.23%), spikelet fertility (81.18%) and 1000 grain weight (25.45 gm) can be utilized as a heat-tolerant variety. Other genotypes Ptb-7 and CR-Dhan 202 seemed to have tolerance traits beneficial at the vegetative stage. The genotype Rajalakshmi can be characterised as heat susceptible as it had significantly lower values for all parameters. Polymorphic analysis was carried out to validate SSR markers associated with heat tolerance. The polymorphic information content (PIC) was found to be the highest for RM236 and RM6100. The SSR marker RM6100 has been validated in the current investigation to be associated with heat tolerance. As the PIC value is an indication of the ability of the marker in indicating genetic diversity, the PIC values of the 11 polymorphic markers is useful for identify heat-tolerant genotypes. The genetic diversity analysis was carried out using DendroUPGMA to establish the relationship between the genotypes. The genotypes Ptb-7 and CR-Dhan 204 were thus found to be closely related to the heat-tolerant check variety, N-22 indicating genetically related traits for tolerance to heat.

Terminal Heat Stress and Its Mitigation Options through Agronomic Interventions in Wheat Crop: A Review

Climate change will be one of the most critical dangers to agriculture in the coming years. On average, abiotic stresses account for 50% of the production losses in agricultural production. Terminal stress is a major environmental issue limiting wheat production in the majority of wheat-growing regions across the world. The term "terminal heat stress" refers to a rise in temperature (&gt; 30°C) after anthesis during grain development which impairs the process of grain filling in wheat. Rising temperatures shorten the vegetative and reproductive periods of the wheat crop, but the reproductive stage is more vulnerable than the vegetative. The major portion of India, including the north-eastern plain zone, the central zone, and the peninsular zone, experienced terminal stress over the summer. There are numerous solutions available for mitigating the harmful effects of terminal heat stress on wheat crops. Adjusting sowing time is one of the most impactful agronomic techniques. Wheat planting methods such as conservation tillage, bed sowing, conventional tillage plus mulch, and surface residue preservation are considered suitable alternatives for mitigating terminal stress. Moreover, irrigation at a critical period reduces terminal heat stress and boosts wheat grain development. Foliar spraying of osmoprotectants such as KNO3, Thiourea, Zn, and many others during anthesis and post-anthesis can also help in alleviating the effects of high-temperature stress on wheat crops.

High-Temperature Stress Effect on the Red Cusk-Eel (Geypterus chilensis) Liver: Transcriptional Modulation and Oxidative Stress Damage.

Simple SummaryThe red cusk-eel (Genypterus chilensis) is a native Chilean species important for aquaculture diversification in Chile. The effect of high-temperature stress on the liver, a key organ for fish metabolism, is unknown. In this study we determined for the first time the effects of high-temperature stress on the liver of red cusk-eel. The results showed that high-temperature stress increased hepatic enzyme activity in the plasma of stressed fish. Additionally, this stressor generated oxidative damage in liver, and generated a transcriptional response with 1239 down-regulated and 1339 up-regulated transcripts associated with several processes, including unfolded protein response, heat shock response and oxidative stress, among others. Together, these results indicate that high-temperature stress generates a relevant impact on liver, with should be considered for the aquaculture and fisheries industry of this species under a climate change scenario.Environmental stressors, such as temperature, are relevant factors that could generate a negative effect on several tissues in fish. A key fish species for Chilean aquaculture diversification is the red cusk-eel (Genypterus chilensis), a native fish for which knowledge on environmental stressors effects is limited. This study evaluated the effects of high-temperature stress on the liver of red cusk-eel in control (14 °C) and high-temperature (19 °C) groups using multiple approaches: determination of plasmatic hepatic enzymes (ALT, AST, and AP), oxidative damage evaluation (AP sites, lipid peroxidation, and carbonylated proteins), and RNA-seq analysis. High-temperature stress generated a significant increase in hepatic enzyme activity in plasma. In the liver, a transcriptional regulation was observed, with 1239 down-regulated and 1339 up-regulated transcripts. Additionally, high-temperature stress generated oxidative stress in the liver, with oxidative damage and transcriptional modulation of the antioxidant response. Furthermore, an unfolded protein response was observed, with several pathways enriched, as well as a heat shock response, with several heat shock proteins up regulated, suggesting candidate biomarkers (i.e., serpinh1) for thermal stress evaluation in this species. The present study shows that high-temperature stress generated a major effect on the liver of red cusk-eel, knowledge to consider for the aquaculture and fisheries of this species.

Physiological Mechanism of Abscisic Acid-Induced Heat-Tolerance Responses to Cultivation Techniques in Wheat and Maize—Review

Abscisic acid (ABA) plays a physiological role in regulating the heat tolerance of plants and maintaining crop productivity under high-temperature stress. Appropriate cultivation techniques can regulate endogenous ABA and help farmers improve food production under high-temperature stress. Here, the physiological basis for ABA-induced heat tolerance in crops is reviewed. High-temperature stress stimulates ABA, which reduces stomatal opening and promotes root growth. The root system absorbs water to maintain the water status, thus allowing the plant to maintain physiological activities under high-temperature stress. ABA plays a synergistic role with nicotinamide adenine dinucleotide biosynthesis to improve the thermal stability of the cell membrane, maintain a dynamic balance between material and energy, and reduce the negative effects of high-temperature stress on kernel number and kernel weight. Cultivation and tillage techniques adapted to high-temperature stress, such as adjustment of sowing time, application of plant growth regulators and fertilizers, and the use of irrigation, subsoiling and heat acclimation, and the mechanisms by which they improve crop heat tolerance, are also reviewed. The results of the studies reviewed here will help researchers develop techniques for cultivating food crops under heat stress and apply them to food-production fields to improve crop productivity.

WGCNA Analysis Identifies the Hub Genes Related to Heat Stress in Seedling of Rice (Oryza sativa L.).

Frequent high temperature weather affects the growth and development of rice, resulting in the decline of seed–setting rate, deterioration of rice quality and reduction of yield. Although some high temperature tolerance genes have been cloned, there is still little success in solving the effects of high temperature stress in rice (Oryza sativa L.). Based on the transcriptional data of seven time points, the weighted correlation network analysis (WGCNA) method was used to construct a co–expression network of differentially expressed genes (DEGs) between the rice genotypes IR64 (tolerant to heat stress) and Koshihikari (susceptible to heat stress). There were four modules in both genotypes that were highly correlated with the time points after heat stress in the seedling. We further identified candidate hub genes through clustering and analysis of protein interaction network with known–core genes. The results showed that the ribosome and protein processing in the endoplasmic reticulum were the common pathways in response to heat stress between the two genotypes. The changes of starch and sucrose metabolism and the biosynthesis of secondary metabolites pathways are possible reasons for the sensitivity to heat stress for Koshihikari. Our findings provide an important reference for the understanding of high temperature response mechanisms and the cultivation of high temperature resistant materials.

Effects of High Temperature Stress on Physiological and Yield Parameters of Mulberry Varieties

High temperature causes alteration in physiological and yield parameters of mulberry plant. The present study was conducted to examine the tolerance/ susceptibility of five popularly cultivated mulberry varieties viz., V1, G2, G4, MR2 and S36 exposed to high temperature stress. The varieties were maintained in Open Top Chambers (OTCs) at 40 ºC for two weeks. It is found that the variety V1 was tolerant to high temperature stress followed by MR2 and S36. After 14 days of high temperature stress, significant differences were observed among the varieties for leaf yield per plant under control and stress conditions compared to control and 7th day after stress. The variety G2 and G4 recorded highest reduction in Total Dry Matter Accumulation (TDMA) (55.60% and 55.96%) at 14th day after stress. Whereas, the lowest reduction percent of TDMA was recorded in V1 (23.06%) followed by MR2 (30.80%) and S36 (36.76%) compared over its control values at 14th day after stress.

Effects of high temperature stress on conchospore germination and early seedling development ofPyropia haitanensis

Pyropia haitanensis is one of the main cultivated macroalgae in China. In recent years, the cultivation of P. haitanensis conchospores in seawater is conducted in advance to obtain earlier harvest. However, the high seawater temperature may exert negative impacts on the algae. Seven temperature conditions (25, 26, 27, 28, 29, 30 and 31°C) were set in the culture of P. haitanensis to investigate the effects of temperature on the conchospore germination and early seedling development of P. haitanensis. The results showed that conchospore germination rate decreased with the increase in temperature. The temperatures of 25 and 26°C were suitable for P. haitanensis conchospore germination. Higher temperature (27°C) promoted conchospore germination on the 1st and 2nd days but decreased the germination considerably on the 3rd day. The conchospore mortality rate reached 89% after culture at high temperature (31°C) for 4 days. Additionally, the development of conchospore seedlings was normal, the total number of cells increased, and the survival rate was high (53%–90%) in the range of 25–29°C. At 25°C, the absolute growth rate of seedlings was as high as 302%. However, the development slowed down and the absolute growth rate decreased with the increase in temperature. At 30 and 31°C, seedling development was abnormal or even ceased, the survival rate was as low as 20% (30°C) and 11% (31°C), and the absolute growth rates were negative under the two conditions. The mortality of seedling was remarkably higher at 31°C than at other temperatures and gradually increased with the increase in temperature (25–31°C). And, the potential mechanisms underlying high temperature damages were analysed. Therefore, the temperature range suitable for the seedling collection and cultivation of P. haitanensis conchospore is 25–29°C.