High Temperature Acclimation Research Articles

Formation of phospholipid nitrogenous bases in euryhaline fish and crustaceans. II. Phosphatidylethanolamine methylation in liver and hepatopancreas

In this report we demonstrate the presence of a phospholipid N-methylation in tissues of fish and crustaceans. In liver and hepatopancreas this pathway participates very actively to the synthesis of different molecular species of PC which are later exchanged with plasma and distributed to the other tissues by the blood flow. In all tissues an enhancing effect of salinity on the biosynthesis of PC through PE methylation is observed in euryhaline fish and crustaceans. The effect of temperature upon this biosynthesis of PC appears specific for each organ. High acclimation temperatures diminish in fish the percentage of PC synthesized through this pathway in all organs. In crustaceans, the effect of temperature is more species dependent.

The interaction of high temperature and elevated CO2on photosynthetic acclimation of single leaves of rice in situ

The interaction of high temperature and elevated CO2on photosynthetic acclimation of single leaves of rice in situ

Thermal modulation of channel catfish intestinal dimensions, BBM fluidity, and glucose transport.

In light of the direct influence of temperature on metabolic rates and dietary loads of ectotherms, intestinal responses were evaluated by measuring 1) dimensions, 2) transapical initial rates of transport using intact tissues and brush-border membrane vesicles (BBMV), and 3) BBMV fluidity using two size groups of channel catfish (Ictalurus punctatus) acclimated to different water temperatures. Intestines of larger fish at 15 degrees C were 23% longer and 61% heavier than those at 30 degrees C. Regardless of assay temperature, rates of glucose uptake by fish held at 30 degrees C relative to those at 15 degrees C were twofold higher for intact tissues and over fivefold higher for BBMV. Although rates of PBMV transport were higher for smaller fish, adaptive responses were greater for larger fish. Temperature coefficients (Q10S) for BBMV transport were higher between 5 and 15 degrees C (3.5-4.5) relative to 15 to 35 degrees C (1.9-2.0) and may be partly related to the inability of catfish held at low temperatures to adjust apical membrane fluidity. Our findings indicate that 1) cold-acclimated catfish maintain transport capacities by increasing intestinal dimensions, 2) high acclimation temperatures increase rates of uptake by as yet unknown mechanisms, 3) thermal modulation of transport varies among species and nutrients, and 4) adaptive responses of ectotherms are different from those of homeotherms).

Protein Synthesis Inhibitors Block High-temperature Acclimation in Bell Pepper Leaves

Pepper (Capsicum annuum L. `Early Calwonder') leaf disks were vacuum-infiltrated in distilled water (control), anisomycin, aurintricarboxylic acid, cycloheximide, ethionine, norvanine, or puromycin to determine whether protein synthesis inhibitors blocked high-temperature acclimation. After infiltration, one-half of the leaf disks were placed in an incubator at 24C as a control, and the other half were kept in a water bath at 38C for 2 h to induce acclimation. Test tubes containing the disks then were placed in a water bath at 50.5C for 0, 1, 5, 10, 15, 25, 35, or 50 minutes. Thermotolerance was evaluated using electrolyte leakage. High-temperature acclimation was blocked in all six protein synthesis-inhibitor treatments. Only control disks infiltrated with distilled water acclimated. It seems that protein synthesis is required for high-temperature acclimation in bell pepper leaves.

Enhanced hypo-osmoregulation induced by warm-acclimation in antarctic fish is mediated by increased gill and kidney Na+/K(+)-ATPase activities.

Serum osmolality and serum inorganic ion concentrations were studied in two antarctic fish species, Trematomus bernacchii and T. newnesi, during 5 weeks of acclimation to 4 degrees C and compared with control values for groups acclimated to -1.5 degrees C. Acclimation to 4 degrees C significantly decreased the serum osmolality of both species, thereby increasing their seawater-to-extracellular fluid (ECF) osmotic gradient. The decline in osmolality with acclimation to 4 degrees C was accompanied by significant and rapid losses of Na+ and Cl- during the first 14 days of acclimation and was maintained throughout the study period. At day 35 of acclimation, the lipid composition and microsomal Na+/K(+)-ATPase specific activities at 4 degrees C and 37 degrees C were determined in membranes from gill, kidney, liver and muscle tissues. No warm-induced decrease in fatty acid unsaturation was found in the tissues of either species. In the gills and kidneys of both species, the Na+/K(+)-ATPase activities assayed at 4 degrees C were increased after acclimation to 4 degrees C. The Na+/K(+)-ATPase activities at 37 degrees C increased at the higher acclimation temperature in T. newnesi kidneys and T. bernacchii gills, but in both species there was no compensation to temperature in the liver, regardless of assay temperature. Muscle Na+/K(+)-ATPase activity decreased in response to warm-acclimation in T. bernacchii and T. newnesi assayed at 4 degrees C and 37 degrees C, respectively. During acclimation to 4 degrees C, the discontinuity in the Arrhenius plot of the Na+/K(+)-ATPase activities of T. newnesi gill moved to a lower temperature, whereas that of kidney remained unchanged. The results indicate that acclimation to 4 degrees C induced a decrease in serum osmolality which resulted from the positive compensation of Na+/K(+)-ATPase in osmoregulatory tissues. The enhancement in Na+/K(+)-ATPase activity at 4 degrees C suggests that energy expenditure in antarctic fish may be lessened, in part, by maintaining a reduced seawater-to-ECF osmotic gradient.

Northern Squawfish,Ptychocheilus oregonensis, O2Consumption Rate and Respiration Model: Effects of Temperature and Body Size

Northern squawfish, Ptychocheilus oregonensis (live weight range 0.361–1.973 kg), O2consumption was measured with temperature-controlled, flow-through respirometers for >24 h. Mean standard O2consumption rate of northern squawfish increased with acclimation temperature: 24.3, 49.1, 75.0, and 89.4 mg∙kg−0.67∙h−1at 9, 15, 18, and 21 °C, respectively. Q10analysis showed that O2consumption rate temperature sensitivity was greatest at the intermediate acclimation temperatures (15–18 °C, Q10 = 4.10), moderate at the lower acclimation temperatures (9–15 °C, Q10 = 3.23), and lowest at the higher acclimation temperatures (18–21 °C, Q10 = 1.80). Overall Q10was 2.96 (9–21 °C). Body size (W, grams) and temperature (T, degrees Celcius) were related to O2consumption ([Formula: see text], grams per gram per day) by [Formula: see text]W−0.285∙e0.105T. Northern squawfish red to white muscle ratios significantly exceeded those of rainbow trout, Oncorhynchus mykiss, in cross sections at 50 and 75% of standard length. High metabolic rates and red to white muscle ratios argue for comparability of northern squawfish with active predators such as sympatric rainbow trout.

Abscisic Acid Accumulation in Leaves and Cultured Cells during Heat Acclimation in Grapes

Heat tolerance and endogenous ABA levels in leaves and cultured grape cells (Vitis spp., cultivars Venus and Veeblanc) were evaluated during beat acclimation. Plants and cultured cells were acclimated at 38 and 36C, respectively. Heat tolerance increased rapidly after exposing plants or cells to acclimation temperatures, reaching a maximum after 10 to 16 hours and 10 to 12 hours for leaves and cultured cells, respectively. Free and bound ABA levels increased sharply during the first hour of heat acclimation, before leaves and cultured cells reached their maximum beat tolerance. The increase in ABA during heat acclimation was 2- to 3-fold that of the nonacclimated control, and the time of the ABA accumulation peak in tissue roughly corresponded to the maximum heat tolerance in leaves and cultured cells. Heat tolerance was induced in cultured cells by exogenous ABA application. Heat tolerance increased significantly after 24 hours of ABA application at 7.6 or 9.5 μm. The results suggest that ABA may be a factor in high-temperature acclimation and beat-tolerance induction in grapes. Chemical name used: abscisic acid (ABA).

Acclimatory responses in enzymatic activity and metabolite concentrations in the tropical scorpion Heterometrus fulvipes

1. 1.|Changes in tissue metabolite concentrations and enzyme activities in the pedipalpal (PM) and heart (HM) muscles of the tropical scorpion Heterometrus fulvipes show that the metabolism in PM and HM is fundamentally reorganized following low (18°C) and high (38°C) temperature acclimation. 2. 2.|Changes in metabolite concentrations show that metabolite biosynthesis showed increases after cold acclimation but decreases after warm acclimation. 3. 3.|Similarly, changes in enzyme activities show a preponderance of glycolysis and HMP shunt activity after cold acclimation, while after warm acclimation glycogenolysis, oxidative metabolism and gluconeogenesis predominated. 4. 4.|Higher metabolite concentrations and enzyme activities both before and after thermal acclimation in HM reflect its greater compensatory abilities.

The effects of temperature on benzo[a]pyrene metabolism and adduct formation in the gulf toadfish,Opsanus beta

In order to examine the effects of temperature on benzo[a]pyrene (BaP) metabolism and adduct formation in the absence of the effects of temperature on uptake, gulf toadfish,Opsanus beta, were given a dose of 0.05 mg/kg(3)H-BaPvia caudal vein cannulae at their acclimation temperatures. (18 or 28°C) or following an acute temperature change (18 to 28°C or 28 to 18°C). After 72h, BaP-derived radioactivity was detected in all tissues examined and, as in otherin vivo studies of fish, the highest levels were found in the bile, the liver and the kidney. Temperature did not affect the total amount of BaP metabolized and excreted to the bile, but there were significant quantitative differences between temperature treatments in the classes of Phase I metabolites accumulated. Fish acclimated to high temperature accumulated more BaP triols and tetrols (breakdown products of highly carcinogenic BaP diol epoxides) than fish acclimated at low temperature regardless of exposure temperature: the proportion of biliary metabolites as tetrols and triols in each of the four temperature treatments (acclimation: exposure temperature), 28:18, 28:28, 18:18 and 18:28°C were 21.3±3.6, 58.1±6.1, 14.2±1.8 and 20.9±3.2% (mean±SEM, n=4), respectively. Significant quantities of BaP-DNA and BaP-hemoglobin adducts were detected; however, only the amounts of BaP-DNA adducts showed sensitivity to temperature. As predicted from our metabolite data, high acclimation or exposure temperature led to a significant increase in the amount of BaP-DNA adducts formed: adduct formation in the temperature treatments, 28:18, 28:28, 18:18 and 18:28°C were 342±52, 526±51, 155±42 and 252±55 fg BaP/ µg DNA (mean±SEM, n=4), respectively. These results are discussed in the context of mechanisms of high temperature-enhancement of carcinogenesis in fish.

High Temperature Acclimation in Pepper Leaves

Electrolyte leakage was used to quantify heat stress injury in `Early Calwonder' pepper (Capsicum annuum L.) leaf disks. Lethal temperatures were estimated from the midpoint of the sigmoidal response curve. An interaction between exposure temperature and duration was observed, with lethal temperatures decreasing linearly from 53 to 46C as exposure duration increased exponentially from 5 to 240 min. Exposure to two 7.5-min periods at 51.5C, interrupted by 4 hours at 21C, resulted in the same injury as a continuous 15-min exposure to 51.5C. Plants grown at 22/20C day/night cycles and held 24 hours at 38/30C had increased their heat tolerance by 3C, 51 to 54C; these plants reacclimated to 52C 48 hours after having been transferred back to 22/20C. Leaf disks acclimated significantly in vitro in 1 hour and were fully acclimated by 4 hours at 38C.

Distribution of California stream fishes: influence of environmental temperature and hypoxia

Metabolic rates of seven fish species were used to assess the importance of temperature and dissolved oxygen as factors affecting longitudinal distributions of stream fish within California drainages. Metabolic rates of all species generally increased at higher acclimation temperatures and with abrupt temperature increases. In response to low dissolved oxygen, four species showed no change in metabolic rates up to a threshold temperature where hypoxia-induced metabolic depression was apparent. These threshold temperatures were near the lethal temperatures for each species. In contrast, two species showed metabolic depressions at every temperature, whereas one showed no depression at any temperature. In general, species occupying similar longitudinal positions in California streams behaved similarly in their metabolic responses. For most species, there was good correspondence between metabolic response and relevant field observations of occurrence. In cases where our analysis predicted species presence in waters where they did not exist, other abiotic factors, such as flow rate, or biotic factors, such as predation or competition, must be considered.

Simulation of Maize Phenology

AbstractIn order to perform reliably, crop simulation models require an accurate treatment of crop phenology. A procedure for simulating maize (Zea mays L.) phenology was developed as a subroutine for a maize growth model which ran on an hourly time step. Maize development is simulated from hourly rates of leaf initiation and appearance during three phases of organ differentiation: juvenile, inductive, and reproductive. Leaf initiation occurs during the first two phases, and is terminated by tassel initiation, at which time final leaf number is established. The timing of tassel initiation during the inductive phase is determined by photoperiod and temperature effects on leaf number. The reproductive phase begins at tassel initiation and ends at silking shortly after the appearance of the last leaf before the tassel. Functions used to calculate leaf numbers and rates of leaf initiation and appearance are taken from published results of phytotron studies. Model estimates of leaf number, and of dates of tassel initiation and silking were compared with those observed from a maize phenology trial conducted at five sites in North America. Estimated dates of silking were also compared with those from other data sets. Estimated leaf numbers were usually within one of those observed at all but one site in the phenology trial, where leaf numbers were overestimated by as much as four leaves. Estimated dates of tassel initiation and silking were usually within 5 d of observed dates except at the warmer sites in Texas where estimated dates preceded observed dates by 5 to 15 d. The data suggest that high temperature acclimation may have resulted in slower rates of development than those predicted at some of the warmer sites. Chilling, acclimation, and other effects on phenology not present in phytotron studies will have to be considered further before the results of these studies may be widely used in models of maize phenology.

Photosynthetic Temperature Acclimation in Eucalyptus Species From Diverse Habitats, and a Comparison With Nerium oleander

The response of net photosynthesis per unit leaf area to growth and measurement temperature was measured for Eucalyptus species from diverse natural habitats in Australia and the results compared to Nerium oleander, a species known to exhibit a large degree of temperature acclimation. Eucalyptus species did not show the same degree of temperature acclimation observed for N. oleander in this and previous studies. Photosynthetic acclimation to temperature varied with species of Eucalyptus, apparently in relation to their subgeneric groupings. The estimated parameter, the preferred temperature for photosynthesis, correlated broadly with temperature conditions in the natural habitat. Estimates of two biochemical parameters, Rubisco (estimated from the initial slope of the A/pI curve) and RuP2 regeneration capacity (calculated from the A/pI curve at high CO2) were found to parallel changes in assimilation rate. High temperature acclimation in the Eucalyptus species differed from that of N. oleander. Low temperature grown species, except E. miniata, had a higher temperature threshold for reversible inactivation of Rubisco. In E. miniata, Rubisco, but not regeneration capacity, was sensitive to high temperatures in low temperature grown plants. High growth temperatures appeared to affect the thermolability of the photosynthetic components of the two E. pauciflora provenances. Low temperature acclimation was similar for N. oleander and most of the Eucalyptus species and was accompanied by an increase in both biochemical parameters. Regeneration capacity was sensitive to low temperatures in high temperature grown E. miniata.

Effect of temperature on rate of water loss in some water boatmen (Hemiptera: Corixidae)

Evaporative water loss was compared in Cenocorixa bifida, Cenocorixa expleta, Cenocorixa blaisdelli, and Callicorixa vulnerata and examined in relation to environmental temperature change. In Ce. bifida, evaporative water loss was also studied with respect to rearing temperature and temperature of adult acclimation. Cenocorixa bifida (reared at 20 °C and acclimated to 20 °C) had the lowest rate of water loss at 20 °C of all species, while Ce. expleta had the highest. This pattern also occurred when the activation energy for water loss among species was compared: Ce. expleta had the lowest and Ce. bifida, the highest. High rearing temperatures and high acclimation temperature both reduced water loss at 20 °C in Ce. bifida. This pattern was also reflected in the activation energy for water loss in the different groups of insects exposed to the various temperatures of emergence or acclimation. These data suggest that cuticle lipids vary among these water boatman species and that changes in the proportions of unsaturated lipids may occur in relation to prior long-term exposure to high temperature. Despite differences in rates of water loss and activation energy for water loss, it appears that temperature does not restrict the distribution of any of these insects.

High-temperature damage and acclimation of the photosynthetic apparatus

The thermosensitivity of delayed fluorescence, the relative values of variable chlorophyll fluorescence and the degree of quenching of 9-aminoacridine fluorescene were studied in the chloroplasts from heat-acclimated and non-acclimated (treated 6 h at 52,5°C) young bean plants. The temperature sensitivity of each parameter studied was defined by that temperature at which chloroplast activity decreased by 50% (T50) of its maximum value. There was appreciable increase in the thermostability of membrane energization in chloroplasts isolated from acclimated and non-acclimated plants compared with the controls. The photosynthetic parameters differed according to the suspending medium and the preacclimation treatment. When chloroplast were suspended in phosphate buffer with the addition of stabilizing compounds (2 M sucrose or 0.5% human serum albumin) the thermostability of the thylakoid membranes increased, as was evident by the increases in T50 of about 8-10° C (sucrose) and 2-5° C (human serum albumin) for all the parameters investigated. Photoinduced quenching of 9-aminoacridine fluorescence decreased to some extent in the presence of protective compounds, but in chloroplasts from acclimated plants the T50 was practically equal to that for their long-lived luminescence under the same conditions. At the thylakoid membrane level, acclimation was clearly manifested as an increased thermostability of photoinduced proton-gradient formation.

High-temperature damage and acclimation of the photosynthetic apparatus

The influence of mono- (K(+)) and divalent (Mg(2+)) cations and protons (pH) on the temperature sensitivity of thylakoid membranes was investigated in three groups of young bean plants (control, heat-acclimated and non-acclimated). Thylakoid-membrane function was monitored by second and millisecond delayed fluorescence and 9-aminoacridine fluorescence quenching. It was established that metal ions at investigated concentrations decreased the thermostability of the photosynthetic parameters - an increase of MgSO4 concentration from 0.1 to 20 mM decreased the temperature of their half-inactivation (T50) by 13°C. At the same time the pH dependence of the thermal stability of these parameters showed a maximum at pH 5.5-6.5. The half-inactivation temperatures of those photosynthetic parameters connected with the ability of the thylakoid membrane to form light-induced proton gradients increased by 6-7°C in the heat-acclimated plants compared with the control. It was assumed that the temperature inactivation of photosynthetic electron transfer and the energization of the thylakoid membrane was determined both by the thermoinduced dissociation of the light-harvesting chlorophyll a/b protein complex from PSII, leading to destruction of the excitation energy transfer to the reaction centres, and by the thermal denaturation of the membrane-protein components. The rate of these processes was probably controlled by the size of the negative surface charge and the viscosity of the thylakoid membrane.

Thermostability of acid phosphatase inSelinum vaginatum Clarke andAcer caesium Wall. grown at low and high altitudes

Acid phosphatase isolated from low altitude grown plants of two high altitude plant species,Selinum vaginatum Clarke andAcer caesium Wall, displayed higher thermostability than that from plants of the same species grown at high altitude. The isozyme composition, however, remained unchanged inSelinum vaginatum. InA. caesium, one of four isozymes, was thermolabile in the samples from high altitude and was lost after 10 min heating of the extracts at 60 °c. In the samples from low altitude, this isozyme was not detected and a band with slightly lower Rf value was present which was thermostable. The described changes in the thermal properties of acid phosphatase reflect an adaptive step towards high temperature acclimation at low altitude.

Concomitant Changes in High Temperature Tolerance and Heat-Shock Proteins in Desert Succulents

Raising the day/night air temperatures from 30 degrees C/20 degrees C to 50 degrees C/40 degrees C increases the high temperature tolerated by Agave deserti, Carnegiea gigantea, and Ferocactus acanthodes by 6 degrees C to 8 degrees C; the increase is about half completed in 3 days and fully completed in 10 days. A 25 to 27 kilodalton protein concomitantly accumulates for all three desert succulents upon transfer to 50 degrees C/40 degrees C, while accumulation of other heat "heat-shock" proteins is species specific. Some of the induced proteins are more abundant at 3 days, while others (including the 25-27 kilodalton protein) remain after completion of high temperature acclimation.

Thermal acclimation of photosynthesis by the arctic plant Saxifraga cernua

The thermal acclimations of net photosynthesis, dark respiration, and photorespiration have been studied in the arctic plant Saxifraga cernua. The gas exchange of whole plants grown to maturity under different temperature regimes was analysed for individual plants transferred from (i) 10 to 20 (referred to as high-temperature acclimation) and (ii) 20 to 5 °C (low-temperature acclimation). High- and low-temperature acclimation resulted in shifts of the leaf temperature optimum for net photosynthesis of whole plants in the direction of the new growth temperature. That the acclimating temperature directly affected the photosynthetic apparatus was indicated by (i) changes in the optimum temperature for gross photosynthesis of whole plants and (ii) a change in the oxygen sensitivity of net photosynthesis after acclimation to a new growth temperature. The change in the optimum temperature for net photosynthesis was also due, in part, to altered dark respiration rates which increased during acclimation to low growth temperatures. These results suggest that such acclimation in arctic species like S. cernua arose as a result of the selective pressure of fluctuating temperatures which are experienced during the growth season to maximize annual growth under arctic and subarctic conditions.

Effects of Photoperiod and Starvation on the Temperature Tolerance of Larvae of the Giant Toad, Bufo marinus

The effect of photoperiod on the heat and cold tolerance of Bufo marinus larvae was greatest under conditions that were potentially lethal. Larvae that were acclimated to high temperatures and long days had a higher critical thermal maximum (CTMax) than those acclimated to short days. Similarly, larvae acclimated to lower temperatures and short days were more tolerant to cold than those acclimated to long days. Larvae responded to periods of starvation in a similar way. At high acclimation temperatures, CTMax was relatively constant while CTMin increased significantly with duration of starvation (became less tolerant), and at low acclimation temperatures, CTMin remained constant and CTMax decreased significantly with starvation. CTMax and CTMin acclimated independently such that tolerance under critical conditions was maximized. The effects of photoperiod and starvation on temperature tolerance were not simple but varied with acclimation temperature.