Negative Effects Of Elevated Temperature Research Articles

Response of aestivum and durum wheat varieties to elevated CO2 and temperature under OTC condition

An experiment was undertaken during rabi season of 2020-2021 and 2021-2022 at experimental field of Division of Environmental Science, ICAR-Indian Agriculture Research Institute (IARI), New Delhi inside Open Top Chambers (OTCs) to study the growth and physiological response of aestivum (HD 3226) and durum wheat (HI 8627) varieties to elevated temperature and CO2 concentration. Results showed that days to maturity hastened under elevated temperature condition. Photosynthesis rate, leaf area index and tiller number of wheat varieties reduced in elevated temperature treatment while elevated CO2 concentration of 550 ppm was able to partially compensate the reduction. In aestivum variety of wheat, transpiration rate significantly reduced in elevated CO2 plus high temperature interaction treatment than ambient while transpiration rate of durum variety remained unaffected. The negative effect of elevated temperature on aboveground biomass was more in aestivum variety than durum variety. Elevated CO2 concentration compensated reduction in aboveground biomass by 5.9% in HD 3226 (aestivum) and by 3.6% in HI 8627 (durum) varieties under elevated temperature condition. Hence elevated CO2 concentration will be able to partially compensate reduced crop growth in both aestivum and durum wheat varieties under high temperature condition.

Predicting the strengths of date fiber reinforced concrete subjected to elevated temperature using artificial neural network, and Weibull distribution

Date palm fiber (DPF) is normally used as fiber material in concrete. Though its addition to concrete leads to decline in durability and mechanical strengths performance. Additionally, due to its high ligno-cellulose content and organic nature, when used in concrete for high temperature application, the DPF can easily degrade causing reduction in strength and increase in weight loss. To reduce these effects, the DPF is treated using alkaline solutions. Furthermore, pozzolanic materials are normally added to the DPF composites to reduce the effects of the ligno-cellulose content. Therefore, in this study silica fume was used as supplementary cementitious material in DPF reinforced concrete (DPFRC) to reduce the negative effects of elevated temperature. Hence this study aimed at predicting the residual strengths of DPFRC enhanced/improved with silica fume subjected to elevated temperature using different models such as artificial neural network (ANN), multi-variable regression analysis (MRA) and Weibull distribution. The DPFRC is produced by adding DPF in proportions of 0%, 1%, 2% and 3% by mass. Silica fume was used as partial substitute to cement in dosages of 0%, 5%, 10% and 15% by volume. The DPFRC was then subjected to elevated temperatures between 200 and 800 °C. The weight loss, residual compressive strength and relative strengths were measured. The residual compressive strength and relative strength of the DPFRC declined with addition of DPF at any temperature. Silica fume enhanced the residual and relative strengths of the DPFRC when heated to a temperature up to 400 °C. To forecast residual compressive strength (RCS) and relative strength (RS), we provide two distinct ANN models. The first layer's inputs include DPF (%), silica fume (%), temperature (°C), and weight loss (%). The hidden layer is thought to have ten neurons. M-I is the scenario in which we use RCS as an output, whereas M-II is the scenario in which we use RS as an output. The ANN models were trained using the Levenberg–Marquardt backpropagation algorithm (LMBA). Both neural networking models exhibit a significant correlation between the predicted and actual values, as seen by their respective R = 0.99462 and R = 0.98917. The constructed neural models M-I and M-II are highly accurate at predicting RCS and RS values. MRA and Weibull distribution were used for prediction of the strengths of the DPFRC under high temperature. The developed MRA was found to have a good prediction accuracy. The residual compressive strength and relative strength followed the two-parameter Weibull distribution.

Mitigation of Elevated CO2 Concentration on Warming-Induced Changes in Wheat Is Limited under Extreme Temperature during the Grain Filling Period

Elevated CO2 concentration (eCO2) generally increases plant growth by improving photosynthesis, but it is unclear whether eCO2 can alleviate the negative effects of elevated temperatures, especially in high-temperature years. Manipulative experiments with elevated [CO2] and temperature were conducted in North China to understand the effect of elevated CO2 concentration and temperature on wheat. The photosynthesis, An–PAR and A–Ci curve parameters, growth period, biomass, yield component, and yield of wheat were investigated under different [CO2] (around 400 and 600 ppm) and temperatures (ambient temperature and ambient temperature +2 °C) for 3 years by using controlled chambers. Results showed that elevated temperature significantly shortened the growth period and decreased the yield and biomass of wheat. Elevated [CO2] significantly increased the maximum net photosynthetic rate (Anmax) but reduced the maximum carboxylation rate (Vcmax) and the maximum electron transport rate (Jmax). The extremely high temperature during the grain filling period in 2019 exerted a serious negative impact on wheat production. Elevated [CO2] stimulated photosynthesis, increased kernel number per spike, and extended the duration of the grain filling period, which consequently increased biomass and grain yield under elevated temperatures in normal years (2018 and 2020). Although the combination of CO2 and temperature reduced photosynthesis and biomass, it also alleviated the negative impact of elevated temperatures on grain yield to some extent under extremely high temperature during the grain filling period in 2019. The mitigative effect of eCO2 under extreme high temperature is limited, and planting early-maturing cultivars or increasing the genotypes of kernel number per spike help to escape the extreme high temperature of the critical growth period.

Elevated CO2 and temperature under future climate change increase severity of rice sheath blight.

Sheath blight (ShB), caused by Rhizoctonia solani, is one of the major threats to rice (Oryza sativa L.) production. However, it is not clear how the risk of rice ShB will respond to elevated CO2 and temperature under future climate change. Here, we conducted, field experiments of inoculated R. solani under combinations of two CO2 levels (ambient and enriched up to 590 μmol mol-1) and two temperature levels (ambient and increased by 2.0°C) in temperature by free-air CO2 enrichment (T-FACE) system for two cultivars (a susceptible cultivar, Lemont and a resistant cultivar, YSBR1). Results indicate that for the inoculation of plants with R. solani, the vertical length of ShB lesions for cv. Lemont was significantly longer than that for cv. YSBR1 under four CO2 and temperature treatments. The vertical length of ShB lesions was significantly increased by elevated temperature, but not by elevated CO2, for both cultivars. The vertical length of ShB lesions under the combination of elevated CO2 and elevated temperature was increased by 21-38% for cv. Lemont and by -1-6% for cv. YSBR1. A significant increase in MDA level was related to a significant increase in the vertical length of ShB lesions under the combination of elevated CO2 and elevated temperature. Elevated CO2 could not compensate for the negative effect of elevated temperature on yield of both cultivars under future climate change. Rice yield and biomass were further decreased by 2.0-2.5% and 2.9-4.2% by an increase in the severity of ShB under the combination of elevated CO2 and elevated temperature. Thus, reasonable agronomic management practices are required to improve both resistance to ShB disease and grain yield for rice under future climate change.

Response mechanisms to ocean warming exposure in Effrenium voratum (Symbiodiniaceae).

Ocean warming is an extreme environment event that has profound and lasting impacts on Symbiodiniaceae. However, their response mechanisms to elevated temperature exposure are poorly understood. In this study, the physiological and transcriptional responses of Effrenium voratum (Symbiodiniaceae) to ocean warming were examined. After exposure to 30°C, no significant variations in growth, chlorophyll a, or photosynthetic and respiration rates were observed, while a higher temperature (34°C) significantly reduced these physiological measurements. Meanwhile, lipid content and fatty acid composition were altered at high temperature (i.e., elevated degree of fatty acid saturation). Such biochemical constituents likely contributed to the mitigation of the negative effects of elevated temperatures. Furthermore, higher expression levels of genes related to the synthesis and elongation of fatty acids were detected at high temperature. The adjustment of lipids and fatty acid composition may be a potential mechanism by which E. voratum may survive under future global warming. ONE SENTENCE SUMMARY: The adjustment of lipids and fatty acid composition may be a potential mechanism by which E. voratum acclimate to future global warming.

Ecdysteroid responses to urban heat island conditions during development of the western black widow spider (Latrodectus hesperus).

The steroid hormone 20-hydroxyecdysone (20E) controls molting in arthropods. The timing of 20E production, and subsequent developmental transitions, is influenced by a variety of environmental factors including nutrition, photoperiod, and temperature, which is particularly relevant in the face of climate change. Environmental changes, combined with rapid urbanization, and the increasing prevalence of urban heat islands (UHI) have contributed to an overall decrease in biodiversity making it critical to understand how organisms respond to elevating global temperatures. Some arthropods, such as the Western black widow spider, Latrodectus hesperus, appear to thrive under UHI conditions, but the physiological mechanism underlying their success has not been explored. Here we examine the relationship between hemolymph 20E titers and spiderling development under non-urban desert (27°C), intermediate (30°C), and urban (33°C) temperatures. We found that a presumptive molt-inducing 20E peak observed in spiders at non-urban desert temperatures was reduced and delayed at higher temperatures. Intermolt 20E titers were also significantly altered in spiders reared under UHI temperatures. Despite the apparent success of black widows in urban environments, we noted that, coincident with the effects on 20E, there were numerous negative effects of elevated temperatures on spiderling development. The differential effects of temperature on pre-molt and intermolt 20E titers suggest distinct hormonal mechanisms underlying the physiological, developmental, and behavioral response to heat, allowing spiders to better cope with urban environments.

The Effects of Temperature, Light, and Feeding on the Physiology of Pocillopora damicornis, Stylophora pistillata, and Turbinaria reniformis Corals

Evidence has shown that individually feeding or reduced light can mitigate the negative effects of elevated temperature on coral physiology. We aimed to evaluate if simultaneous low light and feeding would mitigate, minimize, or exacerbate negative effects of elevated temperature on coral physiology and carbon budgets. Pocillopora damicornis, Stylophora pistillata, and Turbinaria reniformis were grown for 28 days under a fully factorial experiment including two seawater temperatures (ambient temperature of 25 °C, elevated temperature of 30 °C), two light levels (high light of 300 μmol photons m−2 s−1, low light of 150 μmol photons m−2 s−1), and either fed (Artemia nauplii) or unfed. Coral physiology was significantly affected by temperature in all species, but the way in which low light and feeding altered their physiological responses was species-specific. All three species photo-acclimated to low light by increasing chlorophyll a. Pocillopora damicornis required feeding to meet metabolic demand irrespective of temperature but was unable to maintain calcification under low light when fed. In T. reniformis, low light mitigated the negative effect of elevated temperature on total lipids, while feeding mitigated the negative effects of elevated temperature on metabolic demand. In S. pistillata, low light compounded the negative effects of elevated temperature on metabolic demand, while feeding minimized this negative effect but was not sufficient to provide 100% metabolic demand. Overall, low light and feeding did not act synergistically, nor additively, to mitigate the negative effects of elevated temperature on P. damicornis, S. pistillata, or T. reniformis. However, feeding alone was critical to the maintenance of metabolic demand at elevated temperature, suggesting that sufficient supply of heterotrophic food sources is likely essential for corals during thermal stress (bleaching) events.

Effect of dispersing media and temperature on inter-yarn frictional properties of Kevlar fabrics impregnated with shear thickening fluid

Shear thickening fluid (STF) treated Kevlar fabrics is a potential method to improve the stab resistance of flexible body armors, whereas the STFs were significantly influenced by the temperature during their practical application. In this study, four kinds of STFs were prepared using constant silica and various dispersing media with different number of hydroxyl groups and chain length. The steady state and dynamic rheological properties of STFs were investigated in the temperature range of 20 to 50 °C. The pull-out test of the STF/Kevlar fabrics were also studied at different speeds and temperatures to evaluate the contribution of shear thickening effect. The results indicated that the STF/Kevlar fabrics had higher inter-yarn friction than the neat fabrics, suggesting a correlation of shear thickening effect. At 50 °C, the STFs with more hydroxyl groups and longer chains could reduce the negative effect of elevated temperature on the inter-yarn friction from 88.94% to 49.23%. Therefore, according to the different environment temperature, it is necessary to choose suitable dispersing medium to design application-specific of STFs.

Adjustments in fatty acid composition is a mechanism that can explain resilience to marine heatwaves and future ocean conditions in the habitat-forming seaweed Phyllospora comosa (Labillardière) C.Agardh.

Marine heatwaves are extreme events that can have profound and lasting impacts on marine species. Field observations have shown seaweeds to be highly susceptible to marine heatwaves, but the physiological drivers of this susceptibility are poorly understood. Furthermore, the effects of marine heatwaves in conjunction with ocean warming and acidification are yet to be investigated. To address this knowledge gap, we conducted a laboratory culture experiment in which we tested the growth and physiological responses of Phyllospora comosa juveniles from the southern extent of its range (43-31°S) to marine heatwaves, ocean warming and acidification. We used a 'collapsed factorial design' in which marine heatwaves were superimposed on current (today's pH and temperature) and future (pH and temperature projected by 2100) ocean conditions. Responses were tested both during the heatwaves, and after a 7-day recovery period. Heatwaves reduced net photosynthetic rates in both current and future conditions, while respiration rates were elevated under heatwaves in the current conditions only. Following the recovery period, there was little evidence of heatwaves having lasting negative effects on growth, photosynthesis or respiration. Exposure to heatwaves, future ocean conditions or both caused an increase in the degree of saturation of fatty acids. This adjustment may have counteracted negative effects of elevated temperatures by decreasing membrane fluidity, which increases at higher temperatures. Furthermore, P. comosa appeared to down-regulate the energetically expensive carbon dioxide concentrating mechanism in the future conditions with a reduction in δ13 C values detected in these treatments. Any saved energy arising from this down-regulation was not invested in growth and was likely invested in the adjustment of fatty acid composition. This adjustment is a mechanism by which P. comosa and other seaweeds may tolerate the negative effects of ocean warming and marine heatwaves through benefits arising from ocean acidification.

Impaired growth and survival of tropical macroalgae (Sargassum spp.) at elevated temperatures

Increasing ocean temperatures associated with ongoing climate change have resulted in regional reductions in the cover of live coral and increasing concerns that coral reefs will be overgrown by macroalgae. The likelihood of macroalgal overgrowth will, however, depend on the thermal sensitivities of the macroalgae themselves. We exposed recently settled propagules of the common canopy-forming macroalga Sargassum swartzii and adult thalli of three species of Sargassum (S. swatzii, S. cristaefolium, S. polycystum) to three experimental temperatures: ambient, + 2 °C, and + 3.5 °C, reflective of summer minimum, mean, and maximum temperatures for the region. Growth and survival of Sargassum swartzii propagules were assessed over 48 days, and the growth, physical toughness, elemental composition, and susceptibility to herbivory of adult thalli were assessed after short-term exposure (2-weeks) to experimental temperatures. Growth and survival of S. swartzii propagules were reduced by 43% and 84%, respectively, when cultured at the elevated (+ 3.5 °C) temperature compared to ambient temperature. Similarly, elevated temperature resulted in a 17–49% decline in the growth of adult Sargassum thalli relative to controls. Susceptability of S. swartzii and S. cristaefolium to herbivory (i.e. mass removed by herbivores) was 50% less for thalli cultured at elevated (+ 3.5 °C) compared to ambient temperature, but this pattern was not related to changes in the physical or chemical properties of the thalli as a result of elevated temperature. The negative effects of elevated temperatures on the growth and survival of both Sargassum propagules and adult thalli will likely restrict the capacity of Sargassum, and potentially other macroalgae, to establish in new areas, and may also threaten the persistence of existing macroalgal meadows under future ocean temperatures. The thermal sensitivities of tropical Sargassum, together with those of corals, suggest ongoing ocean warming may lead to novel reef ecosystems that are low in both coral cover and macroalgal cover.

Oxidation of reactive azo-dyes with pulsed corona discharge: Surface reaction enhancement

Emissions of textile dyes result in biological hazard. The technology response to the problem of textile dyes suffers unaffordable costs. Application of pulsed corona discharge (PCD) to azo-dyes oxidation requires establishing operation conditions. Experimental studies in oxidation of reactive blue RB4 and RB19 were undertaken with variation of pulse, temperature, electrolyte and surfactant parameters. Application of PCD demonstrated dyes removed at high energy efficiency, up to 340–360 g kW−1 h−1 in presence of a surfactant. Sodium sulphate and chloride reduced RBs’ oxidation efficiencies equally in respect to conductivity with no electrolysis observed. The negative effect of elevated temperature was quantified.

Cover Feature: Cellular Biocatalysts Using Synthetic Genetic Circuits for Prolonged and Durable Enzymatic Activity (ChemBioChem 14/2019)

A genetic logic-gate-based operation can activate a cellular biocatalyst. The biocatalyst needs two different inputs to be activated. Two different approaches were employed to build the AND genetic logic gate, the first approach uses a recombinase-based gate; the other approach uses a toehold-switch-based approach. The Boolean logic gate enables the formation of a biofilm-supported biocatalyst. The first circuit triggers the cell to express alkaline phosphatase and an additional circuit provides the secretion of a biofilm matrix composed of proteins that are called functional amyloids. The biofilm matrix protects the cellular biocatalyst against the negative effects of elevated temperatures. More information can be found in the full paper by U. O. S. Seker et al. on page 1799 in Issue 14, 2019 (DOI: 10.1002/cbic.201800767).

Can Future CO2 Concentrations Mitigate the Negative Effects of High Temperature and Longer Droughts on Forest Growth?

(1) Background: Climate change may subject forests to climate conditions to which they are not adapted. Elevated temperatures can potentially reduce net photosynthesis by increasing respiration rates and increasingly long droughts dramatically increase morbidity. While CO2 enrichment enhances productivity, it is not clear to what extent CO2 enrichment can offset the negative effects of elevated temperatures and longer droughts; (2) Methods: We used a mechanistic landscape model to conduct controlled simulation experiments manipulating CO2 concentration, temperature, drought length and soil water capacity; (3) Results: We found that elevated CO2 stimulates productivity such that it dwarfs the negative effect caused by elevated temperature. Energy reserves were not as strongly mitigated by elevated CO2, and the mortality of less competitive cohorts increased. Drought length had a surprisingly small effect on productivity measures, but longer droughts increased the risk of mortality; (4) Conclusions: Elevated CO2 compensated for the negative effect of longer droughts in terms of productivity measures, but not survival measures.

Physiology of juvenile hydroids - High food availability mitigates stress responses of Hydractinia echinata to increasing seawater temperatures

Ocean warming due to climate change is predicted to profoundly affect marine ecosystems. These effects are expected to be intensified for shelf seas like the North Sea, where sea surface temperatures are predicted to increase 3 °C by 2100. Increasing seawater temperature is suggested to alter physiological performance of benthic marine invertebrates, while predicted changes in ocean dynamics and primary production might limit nutrient availability. At present, the combined effect of temperature and nutrition stress on marine biota is largely understudied. We investigated physiological responses in highly polymorphic hydroids Hydractinia echinata from two locations in the North Sea in response to two temperatures (18 °C = ambient, 21 °C = increased) cross factored with two food regimes (high, low). After 50 days of experimental exposure, morphological (biomass), physiological (standard metabolic rate) and biochemical performance (contents of protein and protein carbonyl) was determined in juvenile hydroids. Reduced growth and low total protein contents combined with high standard metabolic rates and high protein carbonyl contents in H. echinata exposed to 21 °C/low food compared to 18 °C/high food point towards an energy deficiency in the former animals. Meanwhile, high food availability seems to mitigate negative effects of elevated temperature, as energy budgets were sufficient to maintain growth and to keep oxidative damage accumulation low at 21 °C/high food. Our results suggest that high nutrition will increase resilience in juvenile hydroids to seawater temperatures predicted for 2100 in the North Sea. This study illustrates that habitat energy availability is a major driver of species distribution ranges and should be considered in when predicting responses of marine invertebrates to future environmental stressors.

Effect of growth temperature on photosynthetic capacity and respiration in three ecotypes of Eriophorum vaginatum.

Ecotypic differentiation in the tussock‐forming sedge Eriophorum vaginatum has led to the development of populations that are locally adapted to climate in Alaska's moist tussock tundra. As a foundation species, E. vaginatum plays a central role in providing topographic and microclimatic variation essential to these ecosystems, but a changing climate could diminish the importance of this species. As Arctic temperatures have increased, there is evidence of adaptational lag in E. vaginatum, as locally adapted ecotypes now exhibit reduced population growth rates. Whether there is a physiological underpinning to adaptational lag is unknown. Accordingly, this possibility was investigated in reciprocal transplant gardens. Tussocks of E. vaginatum from sites separated by ~1° latitude (Coldfoot: 67°15′N, Toolik Lake: 68°37′, Sagwon: 69°25′) were transplanted into the Toolik Lake and Sagwon sites and exposed to either an ambient or an experimental warming treatment. Five tussocks pertreatment combination were measured at each garden to determine photosynthetic capacity (i.e., V cmax and J max) and dark respiration rate (R d) at measurement temperatures of 15, 20, and 25°C. Photosynthetic enhancements or homeostasis were observed for all ecotypes at both gardens under increased growth temperature, indicating no negative effect of elevated temperature on photosynthetic capacity. Further, no evidence of thermal acclimation in R d was observed for any ecotype, and there was little evidence of ecotypic variation in R d. As such, no physiological contribution to adaptational lag was observed given the increase in growth temperature (up to ~2°C) provided by this study. Despite neutral to positive effects of increased growth temperature on photosynthesis in E. vaginatum, it appears to confer no lasting advantage to the species.

Ecological complexity buffers the impacts of future climate on marine consumers

Ecological complexity represents a network of interacting components that either propagate or counter the effects of environmental change on individuals and communities1–3. Yet, our understanding of the ecological imprint of ocean acidification (elevated CO2) and climate change (elevated temperature) is largely based on reports of negative effects on single species in simplified laboratory systems4,5. By combining a large mesocosm experiment with a global meta-analysis, we reveal the capacity of consumers (fish and crustaceans) to resist the impacts of elevated CO2. While individual behaviours were impaired by elevated CO2, consumers could restore their performances in more complex environments that allowed for compensatory processes. Consequently, consumers maintained key traits such as foraging, habitat selection and predator avoidance despite elevated CO2 and sustained their populations. Our observed increase in risk-taking under elevated temperature, however, predicts greater vulnerability of consumers to predation. Yet, CO2 as a resource boosted the biomass of consumers through species interactions and may stabilize communities by countering the negative effects of elevated temperature. We conclude that compensatory dynamics inherent in the complexity of nature can buffer the impacts of future climate on species and their communities. The complexity of ecosystems could influence how warmer waters and acidification affect marine biota. In this study, whilst individual behaviours were affected by increased CO2, community dynamics buffered the impacts on fish and crustaceans.

Feral horses influence both spatial and temporal patterns of water use by native ungulates in a semi‐arid environment

AbstractThe horse (Equus caballus) is a feral ungulate that currently exceeds target population sizes in many areas of western North America. Horses are behaviorally dominant over native ungulates and outcompete the latter for access to water sources. However, a better understanding of the broader spatial and temporal implications of horse‐induced competition on access to water by native ungulates will enable better conservation and management of native species. Our objective was to determine whether pronghorn (Antilocapra americana) and mule deer (Odocoileus hemionus) spatially or temporally altered their use of water to minimize interactions with horses. From 2010 to 2014, we used remote cameras to monitor ungulates at 32 water sources in the Great Basin Desert. We evaluated spatial and temporal partitioning by these species at water sources using generalized linear models, mixed‐effects models, and Mann–Whitney U tests. We found that both native ungulates used water sources less often where horse activity at water sources was high, indicating that spatial avoidance occurred. Further, we observed significant differences in peak arrival time for pronghorn, but not mule deer at horse‐occupied sites versus sites where horses were absent or uncommon, indicating that temporal avoidance may be more important for pronghorn than mule deer. Because mule deer are primarily crepuscular and nocturnal whereas horses are largely diurnal, we did not expect to observe a temporal shift for mule deer. We also found strong support for the interactive negative effect of elevated temperature and subsequent increased activity of horses at water sources on drinking patterns of pronghorn and mule deer. Our findings indicate that feral horses further constrain access to an already limited resource for native species in a semi‐arid environment.

Effect of elevated CO2 and temperature on growth and yield of wheat grown in sub-humid climate of eastern Indo-Gangetic Plain (IGP)

The atmospheric CO2 will be in the range of 510 to 760 L-1 by the end of 21st century and mean global temperature will be 1.5 to 4.5 oC higher than the present day which has a direct and indirect effect on agriculture. India is a key global region vulnerable to climate change; however, limited studies have focused on the combine effect of CO2 enrichment and temperature on wheat production in Sub-humid climate of eastern IGP in India. To address this issue, an Open top chamber (OTCs) experiment was conducted during 2013-14, to determine the effects of elevated atmospheric carbon dioxide (CO2) and temperature on growth, yield attributes and yield of wheat. Wheat cultivars (DBW 14 and HD 2967) were grown with four treatment combination of CO2 and temperature in OTCs, during the rabi season. The study revealed that wheat genotypes performed better under elevated CO2 condition in term of grain number, test weight and grain yield than an ambient condition. The greater biomass under elevated CO2 was brought about by an increase in radiation use efficiency (RUE) during both heading and physiological maturity periods. Elevated temperature decreased the grain yield but increase plant height compared to ambient temperature. Days to physiological maturity was reduced by 4 to 7 days in both the cultivars under elevated temperature condition and increased by 3 to 4 days under the elevated CO2 condition with respect to ambient condition. The elevated CO2 had positive effects whereas elevated temperature had negative effects on growth, yield attributes and yield of wheat. With elevation of both CO2 and temperature, elevated CO2 compensate the negative effects of elevated temperature on growth, yield attributes and yield of wheat.

Interactive effects of nutrient availability and temperature on growth and survival of different size classes of Saccharina japonica (Laminariales, Phaeophyceae)

:In northern Japan, the production of Saccharina japonica exhibits marked annual fluctuation due to changes in seawater temperature and nutrient availability during winter and spring. To better understand this phenomenon, we examined the combined effects of temperature (5°C, 10°C, 15°C and 20°C) and nutrient availability (seawater enriched with 25% Provasoli's enriched seawater vs nonenriched seawater) on photosynthesis, growth and survival and nitrogen and chlorophyll a contents of juvenile sporophytes (2–3 cm) and larger size class sporophytes (100–150 cm) from southern Hokkaido. Both juvenile sporophytes and discs from 100–150-cm-class sporophytes cultured in enriched seawater showed significantly higher growth rates and photosynthetic activities than those cultured in nonenriched seawater. This difference likely was due to the significantly higher nitrogen and chlorophyll a contents of thalli grown in enriched seawater. Significant effects of temperature on growth and photosynthesis were also detected. A significant interaction between temperature and nutrient availability for relative growth rate (RGR) was detected. The positive effect of elevated nutrient availability on RGRs was magnified by an increase in temperature from 5°C to 15°C for juvenile sporophytes and from 5°C to 10°C for 100–150-cm-class sporophytes; whereas, the negative effect of elevated temperature from 10°C to 15°C on RGRs of 100–150-cm-class sporophytes was antagonised by a reduction in nutrient availability. In contrast to the 100% survival rate in enriched seawater, dead juvenile sporophytes and discs from 100–150-cm-class sporophytes were found at 15°C and 20°C in nonenriched seawater, and the survival rates decreased with increasing temperature. Therefore, the growth and survival of sporophytes of S. japonica are significantly affected by nutrient availability and temperature, which may lead to marked fluctuations in annual production.

Interactive effects of elevated summer temperature, nutrient availability, and irradiance on growth and chemical compositions of juvenile kelp, Eisenia bicyclis

SUMMARYPrevious experiments with a factorial design have revealed the effects of several environmental factors on species performance and their interactions, which indicate synergistic or antagonistic effects. Temperature, nutrient availability, and irradiance are well‐known environmental factors that affect the growth and chemical composition of brown algae. However, relatively few studies have tested their combined effect on brown algal growth and chemical composition using a three‐way factorial design. We conducted a culture experiment to test the combined effects of elevated summer temperatures (23 and 26°C), irradiance (180 and 30 μmol photon m−2 s−1), and nutrient availability (enriched and non‐enriched seawater) on four relative growth rates (RGRs; based on wet weight, blade width, length, and area) and three chemical compositions (including carbon, nitrogen, and phlorotannin content) in juvenile sporophytes of the kelp Eisenia bicyclis. RGR based on blade width was the most sensitive to abiotic factors among all RGRs. A significant interaction between temperature and nutrient availability on this RGR suggested that the negative effect of elevated temperature was antagonized by a reduction in nutrient availability. Similarly, the positive effect of elevated irradiance on carbon content was synergized by reduced nutrient availability. Moreover, the negative effect of increased irradiance on nitrogen content was antagonized by elevated temperature in nutrient‐enriched treatments, but not in non‐enriched treatments. The content of carbon‐based phlorotannins increased with reduced nutrient availability but not with elevated irradiance. These results suggest that these abiotic factors have complex interactions on the growth and chemical composition of this species.