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1.
《Environmental and Experimental Botany》2011,71(2-3):212-216
To gain a physiological understanding of the effects of high temperatures on cucumber (Cucumis sativus L.), we subjected seedlings to heat treatment at daytime temperatures of 28 °C, 32 °C, and 36 °C for 7 h a day for 30 days. The amount of active oxygen species, indicators of senescence, and photosynthetic properties in the second and third leaves were determined at the start of temperature treatment and on the 15th and 30th days of treatment. The amount of active oxygen species superoxide in leaves was greatest in the high temperature zones on the 15th day of treatment, and the amount of hydrogen peroxide was greatest in the high temperature zones on both the 15th and 30th days of treatment. The reduction in the amount of protein and the increase in the amount of malondialdehyde, both indicators of senescence, were greatest in the high temperature zones on both the 15th and 30th days of treatment, and the amount of chlorophyll was lowest in the 36 °C zone on the 15th day, and lower in the high temperature zones on the 30th day. It is clear from these results that a large amount of active oxygen species is generated and accumulated in the leaves at high temperatures, and senescence is significantly accelerated. The photosynthetic properties of stomatal conductance, sub-stomatal CO2 concentration, and transpiration rate were at the same level on both the 15th and 30th days of treatment in all three temperature treatment zones. No significant difference was seen in the net photosynthesis rate between the 28 °C and 32 °C zones, was lower in the 36 °C zone than the 32 °C zone on the 15th day, and lowest in the 36 °C zone on the 30th day. CO2 intake and water absorption are only mildly affected by high temperatures, and the reduction in net photosynthesis rate due to the 36 °C high temperature stress suggests that the large amount of active oxygen species induces inhibition of photosynthesis and damage to the mechanism of photosynthesis. 相似文献
2.
《Environmental and Experimental Botany》2006,55(1-2):183-194
The effect of relative humidity (RH) and temperature on CO2 assimilation (An), stomatal conductance (Sc), transpiration rate (Tr), chlorophyll content, fresh and dry weight, leaf length, leaf area, leaf width, formation of new root and survival rate have been assayed in Doritaenopsis in growth chamber after 1 month of acclimatization. Reduced growth was observed at below and above 25 °C whereas it was increased with increasing humidity. Relative water content (RWC) was decreased at 50% and 70% humidity after second day of transfer and recovered completely with the progression of acclimatization. RWC also reduced at high temperature but recovered slowly and a gradual decrease of RWC was observed at 15 °C. A visual symptom of severe leaf tip burn was observed at 50–70% humidity and at 35 °C during acclimatization. At 15 °C and 50% humidity sudden decrease of photosynthetic efficiency (Fv/Fm) was observed, which could not recover in temperature treated plantlets during acclimatization period. Chlorophyll content increased with increasing humidity and at 15 and 35 °C chlorophyll content was decreased compared to 25 °C. Chlorophyll a/b ratio was unchanged while total chlorophyll/carotenoids ratio was increased from low to high temperature. Exposure of plantlets to high temperature led to a noticeable decrease in An, Sc and Tr, and at 15 °C they were more decreased whereas significant differences were not observed in the parameters tested under humidity after 25 days of acclimatization. During daytime at 15 °C, increase in An, Sc and Tr indicates the plantlets adaptability in the new environment. The peroxidase activity remained unaffected in all humidity stress whereas low temperature increased the peroxidase activity compared to high temperature. These finding suggests that photosynthetic properties was greatly affected by air temperature conditions with a reduction of An, Sc and Tr at 15 and 35 °C compared to humidity stress that played a greater role in limiting photosynthesis. 相似文献
3.
The aim of this study was to compare two Portuguese (Alentejana and Mertolenga) and two exotic (Frisian and Limousine) cattle breeds in terms of the relationship between the increase in ambient temperature and the responses of the evaporative heat loss pathways and the effects on homeothermy. In the experiment, six heifers of the Alentejana, Frisian, and Mertolenga breeds and four heifers of the Limousine breed were used. The animals were placed in four temperature levels, the first one under thermoneutral conditions and the other ones with increase levels of thermal stress. When submitted to severe heat stress, the Frisian developed high thermal tachypnea (125 mov/min) and moderate sweating rates (117 g m−2 h−1), which did not prevent an increase in the rectal temperature (from 38.4 °C to 40.0 °C). Moderate increases in rectal temperature were observed in the Alentejana (from 38.8 °C to 39.4 °C) and Limousine (from 38.6 °C to 39.4 °C), especially in the period of highest heat stress. The Limousine showed moderate levels of tachypnea (101 mov/min) while showing the lowest sweating rates. The Alentejana showed significant increases in sweating rate (156 g m−2 h−1) that played a major role in homeothermy. The Mertolenga showed a superior stability of body temperature, even in the period of highest heat stress (from 38.5 °C to 39.1 °C). Uncommonly, the maintenance of homeothermy during moderate heat stress was achieved primarily by intense tachypnea (122 mov/min). The sweating rate remained abnormally low under conditions of moderate heat stress, rising significantly (110 g m−2 h−1) without evidence of stabilization, only when tendency for heat storage occurred. This unusual response of the evaporative heat loss pathways infers a different thermoregulatory strategy, suggesting a different adaptation to semi-arid environment and strong association with water metabolism. 相似文献
4.
《Aquatic Botany》2005,81(2):157-173
The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Thau lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 °C, 982 μmol O2 g−1 dw h−1 and 9.1 μmol O2 g−1 dw h−1/μmol photons m−2 s−1, respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 °C, 583 μmol O2 g−1 dw h−1 and 2.6 μmol O2 g−1 dw h−1/μmol photons m−2 s−1 respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to Rd (ranging 6.7–794 μmol O2 g−1 dw h−1, respectively for Rytiphlaea tinctoria at 7 °C and for Dasya sessilis at 25 °C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of P/I curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species (Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others (N. noltii, Zostera marina, Chaetomorpha linum). 相似文献
5.
《Enzyme and microbial technology》2013,52(6-7):354-358
This work aimed to assess the effect of sub-/super-critical CO2 on the structure and activity of Candida rugosa Lip7 (CRL7) in its solution form. The structure was examined by SDS-PAGE gel electrophoresis, circular dichroism (CD) and fluorescence spectra photometry. Results revealed that the primary structure remained intact after sub-/super-critical CO2 treatment, and the secondary structure altered at the pressure of 10 MPa and temperature 40 °C for 30 min incubation, but it was reflex to its native form with increasing incubation time up to 150 min under 10 MPa and 40 °C. Meanwhile, the tertiary structure via fluorescence spectra analysis showed that the intensity of the maximal emission wavelength at 338 nm decreased under the conditions of 10 MPa and 40 °C for 150 min. Furthermore, the residue hydrolysis activity and kinetics constants (Vmax and Km) of CRL7 treated with sub-/super-critical CO2 were also investigated. In cases of 6 MPa and 35 °C, or 10 MPa and 40 °C for 30 min, activity variance of CRL7 was maybe caused by its secondary structure alteration. But in case of 10 MPa and 40 °C for 150 min, the tertiary structure change was perhaps responsibility for CRL7 activity enhancement. 相似文献
6.
Per Larsson Kristýna Večeřová Hana Cempírková Knut Asbjørn Solhaug Yngvar Gauslaa 《Environmental and Experimental Botany》2009,67(1):215-221
This study aimed to assess biomass growth as a response variable in lichens during short-term laboratory experiments. To do this, we studied the influence of UV-B and temperature on lichen performance including the synthesis of solar radiation screening cortical compounds. The pioneer lichen Xanthoria aureola from exposed sea cliffs and the old forest lichen Lobaria pulmonaria were cultivated for 15 days in the laboratory in a factorial experiments with temperature (12 and 21 °C) and UV-B (0, 0.1, 0.3 and 1.0 W m?2) as treatments. Prior to the experiment, the cortical pigment parietin was non-destructively extracted from X. aureola, whereas the sampled shade-adapted thalli of L. pulmonaria lacked cortical melanic compounds. Therefore both lichens were deficient in cortical sun-screening compounds when the UV-B exposure started. At 12 °C, the relative growth rate was 7.2 ± 0.6 and 3.0 ± 0.8 mg g?1 day?1 in L. pulmonaria and X. aureola, respectively, reduced to 1.8 ± 0.5 and ?2.6 ± 0.9 mg g?1 day?1, at 21 °C. These figures showed that lichen growth is a useful response variable in short-term laboratory experiments. Growth was not influenced by UV-B alone in these pigment-deficient transplants, suggesting that UV-B had little adverse effects on either of the lichen bionts. The cortical sun screens (parietin and melanic compounds) were synthesized in the presence of UV-B, and increased statistically significantly with increasing UV-B at both cultivation temperatures. However, in X. aureola the synthesis was highest at the lowest temperature (12 °C). At 12 °C, changes in chlorophylls, Fv/Fm and NPQ during cultivation were consistent with a substantial level of acclimation to the growth chamber conditions for both species, whereas strong reductions in photosynthetic pigments, Fv/Fm and ФII at 21 °C indicated serious damage and chlorophyll degradation at high temperature. In conclusion, lichen growth and the synthesis of protective compounds are highly responsive lichen processes in short-term experiments. 相似文献
7.
The introduced shrub Tamarix ramosissima invades riparian zones, but loses competitiveness under flooding. Metabolic effects of flooding could be important for T. ramosissima, but have not been previously investigated. Photosynthesis rates, stomatal conductance, internal (intercellular) CO2, transpiration, and root alcohol dehydrogenase (ADH) activity were compared in T. ramosissima across soil types and under drained and flooded conditions in a greenhouse. Photosynthesis at 1500 μmol quanta m−2 s−1 (A1500) in flooded plants ranged from 2.3 to 6.2 μmol CO2 m−2 s−1 during the first week, but A1500 increased to 6.4–12.7 μmol CO2 m−2 s−1 by the third week of flooding. Stomatal conductance (gs) at 1500 μmol quanta m−2 s−1 also decreased initially during flooding, where gs was 0.018 to 0.099 mol H2O m−2 s−1 during the first week, but gs increased to 0.113–0.248 mol H2O m−2 s−1 by the third week of flooding. However, photosynthesis in flooded plants was reduced by non-stomatal limitations, and subsequent increases indicate metabolic acclimation to flooding. Root ADH activities were higher in flooded plants compared to drained plants, indicating oxygen stress. Lower photosynthesis and greater oxygen stress could account for the susceptibility of T. ramosissima at the onset of flooding. Soil type had no effect on photosynthesis or on root ADH activity. In the field, stomatal conductance, leaf water potential, transpiration, and leaf δ13C were compared between T. ramosissima and other flooded species. T. ramosissima had lower stomatal conductance and water potential compared to Populus deltoides and Phragmites australis. Differences in physiological responses for T. ramosissima could become important for ecological concerns. 相似文献
8.
《农业工程》2014,34(1):66-71
Burned and unburned mineral soils (0–10 cm) from a 40-year-old Chinese fir (Cunninghamia lanceolata) forest in Nanping, Fujian, China were incubated for 90 days at different temperatures (25 °C and 35 °C) and humidity [25%, 50%, and 75% of water holding capacity (WHC)] conditions. Carbon (C) mineralization of all soils was determined using CO2 respiration method. The results showed that CO2 evolution rates of the burned and control soils exhibited similar temporal patterns, and similar responses to temperature and moisture. CO2 evolution rates for all soil samples decreased with incubation time. At different humidity conditions, average rate of C mineralization and cumulative mineralized C from burned and control soils were significantly higher at 35 °C than at 25 °C. This implied that C mineralization was less sensitive to soil moisture than to temperature. In both soils at 25 °C or 35 °C, the amount of soil evolved CO2 over the 90 days incubation increased with increasing moisture content from 25% to 75% WHC. A temperature coefficient (Q10) varied with soil moisture contents. The maximum values recorded for Q10 were 1.7 in control soil and 1.6 in burned soil both at 25% WHC. However, there were no significant differences in Q10 values between the control and burned soils over all moisture ranges (P > 0.05). The data of cumulative C–CO2 released from control and burned soils were fitted to two different kinetic models. The two simultaneous reactions model described mineralization better than the first-order exponential model, which reflected the heterogeneity of substrate quality. Based on these results, it is possible to conclude that temperature and moisture are important in the controls of C mineralization, and the combined effects of these variables need to be considered to understand and predict the response of CO2 release in subtropical ecosystems to climate change. 相似文献
9.
《Environmental and Experimental Botany》2008,62(3):224-236
Global atmospheric carbon dioxide concentrations (Ca) are rising. As a consequence, recent climate models have projected that global surface air temperature may increase 1.4–5.8 °C with the doubling of Ca by the end of the century. Because, changes in Ca and temperature are likely to occur concomitantly, it is important to evaluate how the temperature dependence of key physiological processes are affected by rising Ca in major crop plants including maize (Zea mays L.), a globally important grain crop with C4 photosynthetic pathway. We investigated the temperature responses of photosynthesis, growth, and development of maize plants grown at five temperature regimes ranging from 19/13 to 38.5/32.5 °C under current (370 μmol mol−1) and doubled (750 μmol mol−1) Ca throughout the vegetative stages using sunlit controlled environmental chambers in order to test if the temperature dependence of these processes was altered by elevated Ca. Leaf and canopy photosynthetic rates, C4 enzyme activities, leaf appearance rates, above ground biomass accumulation and leaf area were measured. We then applied temperature response functions (e.g., Arrhenius and Beta distribution models) to fit the measured data in order to provide parameter estimates of the temperature dependence for modeling photosynthesis and development at current and elevated Ca in maize. Biomass, leaf area, leaf appearance rate, and photosynthesis measured at growth Ca was not changed in response to CO2 enrichment. Carboxylation efficiency and the activities of C4 enzymes were reduced with CO2 enrichment indicating possible photosynthetic acclimation of the C4 cycle. All measured parameters responded to growth temperatures. Leaf appearance rate and leaf photosynthesis showed curvilinear response with optimal temperatures near 32 and 34 °C, respectively. Total above ground biomass and leaf area were negatively correlated with growth temperature. The dependence of leaf appearance rate, biomass, leaf area, leaf and canopy photosynthesis, and C4 enzyme activities on growth temperatures was comparable between current and elevated Ca. The results of this study suggest that the temperature effects on growth, development, and photosynthesis may remain unchanged in elevated Ca compared with current Ca in maize. 相似文献
10.
Haberlea rhodopensis is a homoiochlorophyllous resurrection plant that shows a low rate of leaf net CO2 uptake (4–6 μmol m?2 s?1) under saturating photosynthetic photon flux densities in air (21% O2 and about 390 ppm CO2). However, leaf net CO2 uptake reaches values of 17–18 μmol m?2 s?1 under saturating CO2 and light. H. rhodopensis leaves have a very low mesophyll CO2 conductance that can partly explain the low rate of leaf net CO2 uptake in normal air. Experimental evidences suggest that mesophyll conductance is not sensitive to temperature in the 20–35 °C range. In addition, it is shown that the (1) transpiration rate of H. rhodopensis is nearly linearly related to the vapour pressure difference between the leaf and the ambient air within the interval from 0.5 kPa to 2.5 kPa at a leaf temperature of 25 °C and (2) leaf net CO2 uptake in normal air under saturating light does not change much with leaf temperature (between 20 °C and 30 °C). At a leaf relative water content of between 90% and 30%, the decrease of leaf net CO2 assimilation during drought can be explained by a decrease of leaf CO2 diffusional conductance. Accordingly the non-photochemical chlorophyll fluorescence quenching decreases only at relative water contents lower than 20%, indicating that photosynthetic activity maintains a trans-thylakoidal proton gradient over a wide range of leaf water contents. Moreover, PSII photochemistry (as estimated by the Fv/Fm ratio and the thermoluminescence B band intensity) is only affected at leaf relative water contents lower than about 20%, thus confirming that primary photosynthetic reactions are resistant to drought. Interestingly, the effect of leaf desiccation on photosynthetic capacity, measured at very high ambient CO2 molar ratios under saturating PPFD, is identical to that observed for three non-resurrection C3 mesophytes. This demonstrates that the photosynthetic apparatus of H. rhodopensis is not more resistant to desiccation when compared to other C3 plants. Since the leaf area decreases by more than 50% when the leaf relative water content is reduced to about 40% during drought it is supposed, following Farrant et al. [Farrant, J.M., Vander, W.C., Lofell, D.A., Bartsch, S., Whittaker, A., 2003. An investigation into the role of light during desiccation of three angiosperms resurrection plants. Plant Cell Environ. 26, 1275–1286], that H. rhodopensis leaf cells avoid mechanical stress. 相似文献
11.
Soo Chool Lee Ho Jin Chae Soo Jae Lee Yong Hee Park Chong Kul Ryu Chang Keun Yi Jae Chang Kim 《Journal of Molecular Catalysis .B, Enzymatic》2009,56(2-3):179-184
A novel potassium-based dry sorbent (KZrI) was developed for CO2 capture at a low temperature range between 50 °C and 200 °C. The CO2 absorption and regeneration properties of this novel regenerable potassium-based dry sorbent were measured in a fixed-bed reactor during multiple absorption/regeneration cycles at low temperature conditions (CO2 absorption at 50–100 °C and regeneration at 130–200 °C). The total CO2 capture capacity of the KZrI sorbent was maintained during the multiple CO2 absorption/regeneration cycles. The XRD patterns and FTIR analyses of the sorbents after CO2 absorption showed the KHCO3 phase only except for the ZrO2 phase used as support. Even after 10 cycles, any other new structures resulting from the by-product during CO2 absorption were not observed. This phase could be easily converted into the original phase during regeneration, even at a low temperature (130 °C). The KZrI sorbent developed in this study showed excellent characteristics in CO2 absorption and regeneration in that it satisfies the requirements of a large amount of CO2 absorption (91.6 mg CO2/g sorbent) and the complete regeneration at a low temperature condition (1 atm, 150 °C) without deactivation. 相似文献
12.
Omera B. Matoo Anna V. Ivanina Claus Ullstad Elia Beniash Inna M. Sokolova 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2013,164(4):545-553
Marine bivalves such as the hard shell clams Mercenaria mercenaria and eastern oysters Crassostrea virginica are affected by multiple stressors, including fluctuations in temperature and CO2 levels in estuaries, and these stresses are expected to be exacerbated by ongoing global climate change. Hypercapnia (elevated CO2 levels) and temperature stress can affect survival, growth and development of marine bivalves, but the cellular mechanisms of these effects are not yet fully understood. In this study, we investigated whether oxidative stress is implicated in cellular responses to elevated temperature and CO2 levels in marine bivalves. We measured the whole-organism standard metabolic rate (SMR), total antioxidant capacity (TAOC), and levels of oxidative stress biomarkers in the muscle tissues of clams and oysters exposed to different temperatures (22 and 27 °C) and CO2 levels (the present day conditions of ~ 400 ppm CO2 and 800 ppm CO2 predicted by a consensus business-as-usual IPCC emission scenario for the year 2100). SMR was significantly higher and the antioxidant capacity was lower in oysters than in clams. Aerobic metabolism was largely temperature-independent in these two species in the studied temperature range (22–27 °C). However, the combined exposure to elevated temperature and hypercapnia led to elevated SMR in clams indicating elevated costs of basal maintenance. No persistent oxidative stress signal (measured by the levels of protein carbonyls, and protein conjugates with malondialdehyde and 4-hydroxynonenal) was observed during the long-term exposure to moderate warming (+ 5 °C) and hypercapnia (~ 800 ppm CO2). This indicates that long-term exposure to moderately elevated CO2 and temperature minimally affects the cellular redox status in these bivalve species and that the earlier observed negative physiological effects of elevated CO2 and temperature must be explained by other cellular mechanisms. 相似文献
13.
The objective of this work was to compare the properties of free and immobilized β-galactosidase (Aspergillus oryzae), entrapped in alginate–gelatin beads and cross-linked with glutaraldehyde. The free and immobilized forms of the enzyme showed no decrease in enzyme activity when incubated in buffer solutions in pH ranges of 4.5–7.0. The kinetics of lactose hydrolysis by the free and immobilized enzymes were studied at maximum substrate concentrations of 90 g/L and 140 g/L, respectively, a temperature of 35 °C and a pH of 4.5. The Michaelis–Menten model with competitive inhibition by galactose fit the experimental results for both forms. The Km and Vm values of the free enzyme were 52.13 ± 2.8 mM and 2.56 ± 0.3 gglucose/L min mgenzyme, respectively, and were 60.30 ± 3.3 mM and 1032.07 ± 51.6 glactose/min m3catalyst, respectively, for the immobilized form. The maximum enzymatic activity of the soluble form of β-galactosidase was obtained at pH 4.5 and 55 °C. Alternatively, the immobilized form was most active at pH 5.0 at 60 °C. The free and immobilized enzymes presented activation energies of 6.90 ± 0.5 kcal/mol and 7.7 ± 0.7 kcal/mol, respectively, which suggested that the immobilized enzyme possessed a lower resistance to substrate transfer. 相似文献
14.
The functional properties of extremophilic Dictyoglomus thermophilum xylanase (XYNB) and the N-terminal disulphide-bridge mutant (XYNB-DS) were studied at high pressure and temperature. The enzymes were quite stable even at the pressure of 500 MPa at 80 °C. The half-life of inactivation in these conditions was over 30 h. The inactivation at 80 °C in atmospheric pressure was only 3-times slower. The increase of pressure up to 500 MPa at 80 °C decreased only slightly the enzyme's stability, whereas in 500 MPa the increase of temperature from 22 to 80 °C decreased significantly more the enzyme's stability. While the high temperature (80–100 °C) decreased the enzyme reaction with short xylooligosaccharides (xylotetraose and xylotriose), the high pressure (100–300 MPa) had an opposite effect. The temperature of 100 °C strongly increased the Km but did not affect the kcat to the same extent, thus indicating that the interaction of the substrate with the active site suffers before the catalytic reaction begins to decrease as the temperature rises. Circular dichroism spectroscopy showed the high structural stability of XYNB and XYNB-DS at 93 °C. 相似文献
15.
Thermal limits of insects can be influenced by recent thermal history: here we used thermolimit respirometry to determine metabolic rate responses and thermal limits of the dominant meat ant, Iridomyrmex purpureus. Firstly, we tested the hypothesis that nest surface temperatures have a pervasive influence on thermal limits. Metabolic rates and activity of freshly field collected individuals were measured continuously while ramping temperatures from 44 °C to 62 °C at 0.25 °C/minute. At all the stages of thermolimit respirometry, metabolic rates were independent of nest surface temperatures, and CTmax did not differ between ants collected from nest with different surface temperatures. Secondly, we tested the effect of brain control on upper thermal limits of meat ants via ant decapitation experiments (‘headedness’). Decapitated ants exhibited similar upper critical temperature (CTmax) results to living ants (Decapitated 50.3±1.2 °C: Living 50.1±1.8 °C). Throughout the temperature ramping process, ‘headedness’ had a significant effect on metabolic rate in total (Decapitated V̇CO2 140±30 µl CO2 mg−1 min−1: Living V̇CO2 250±50 CO2 mg−1 min−1), as well as at temperatures below and above CTmax. At high temperatures (>44 °C) pre- CTmax the relationships between I. purpureus CTmax values and mass specific metabolic rates for living ants exhibited a negative slope whilst decapitated ants exhibited a positive slope. The decapitated ants also had a significantly higher Q10:25–35 °C when compared to living ants (1.91±0.43 vs. 1.29±0.35). Our findings suggest that physiological responses of ants may be able to cope with increasing surface temperatures, as shown by metabolic rates across the thermolimit continuum, making them physiologically resilient to a rapidly changing climate. We also demonstrate that the brain plays a role in respiration, but critical thermal limits are independent of respiration levels. 相似文献
16.
Temperature compensation in whole-animal metabolic rate is one of the responses thought, controversially, to characterize insects from low temperature environments. Temperature compensation may either involve a change in absolute values of metabolic rates or a change in the slope of the metabolic rate – temperature relationship. Moreover, assessments of compensation may be complicated by animal responses to fluctuating temperatures. Here we examined whole animal metabolic rates, at 0 °C, 5 °C, 10 °C and 15 °C, in caterpillars of the sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae), following one week acclimations to 5 °C, 10 °C and 15 °C, and fluctuating temperatures of 0–10 °C, 5–15 °C, and 10–20 °C. Over the short term, temperature compensation was found following acclimation to 5 °C, but the effect size was small (3–14%). By comparison with caterpillars of 13 other lepidopteran species, no effect of temperature compensation was present, with the relationship between metabolic rate and temperature having a Q10 of 2 among species, and no effect of latitude on temperature-corrected metabolic rate. Fluctuating temperature acclimations for the most part had little effect compared with constant temperatures of the same mean value. Nonetheless, fluctuating temperatures of 5–15 °C resulted in lower metabolic rates at all test temperatures compared with constant 10 °C acclimation, in keeping with expectations from the literature. Absence of significant responses, or those of large effect, in metabolic rates in response to acclimation, may be a consequence of the unpredictable temperature variation over the short-term on sub-Antarctic Marion Island, to which P. marioni is endemic. 相似文献
17.
S.T. Yoon Gerrit Hoogenboom Ian Flitcroft Mohammad Bannayan 《Environmental and Experimental Botany》2009,67(1):178-187
An increase in atmospheric CO2 concentration ([CO2]) together with other climate change factors could greatly affect agricultural productivity. Understanding the impact of the change in atmospheric [CO2] in conjunction with the ongoing global change is crucial to prepare for mitigation and any adaptation for future agricultural production. The main goal of this project was to study the time-course pattern of cotton plant growth in response to [CO2] and temperature to investigate the hypothesis that whether response to elevated [CO2] would change at different temperatures. An experiment was conducted in the controlled-environment chambers of the Georgia Envirotron with two different day/night temperatures levels, e.g., 25/15 °C and 35/25 °C, and three CO2 concentrations, e.g., 400, 600 and 800 μmol l?1. The experimental design was completely randomized with four replicates (plastic containers) per treatment. Growth analysis was conducted at bi-weekly intervals during the growing season. In addition, leaf area, leaf dry mass, root dry mass, square dry mass, boll dry mass and total above dry mass per plant were also measured at each sampling. Plant traits, including plant height, number of leaves, number of squares and number of bolls were recorded weekly. The number of days to emergence, squaring, flowering and maturity were also observed. The results showed that by increasing [CO2] to 600 μmol l?1 total biomass increased at both temperature levels, but a further increase of [CO2] up to 800 μmol l?1 increased total biomass only at the temperature of 35/25 °C. Throughout the growing season, there was no significant effect of [CO2] levels on LAI. Increasing temperature from 25/15 °C to 35/25 °C had a positive impact on LAI across all CO2 levels (P < 0.05). Increasing CO2 from 400 to 600 μmol l?1 significantly increased the number of squares by 31.4%, but a further increase to 800 μmol l?1 caused a 6.6% decrease (non-significant) in the number of squares. The interactive effects of [CO2] and temperature indicated that at a higher temperature, CO2 would be more beneficial as we proceed towards the end of the growing season. However, further studies are needed to really understand the interaction between higher [CO2] and temperature levels and cultivar characteristics. 相似文献
18.
《Environmental and Experimental Botany》2008,62(3):281-290
Climate change factors interact to modify plant growth and development. The objective of this study was to evaluate the response to temperature of big bluestem (Andropogon gerardii Vitman) development, growth, reproduction and biomass partitioning under low and high carbon dioxide concentrations ([CO2]) grown in controlled environmental conditions. Ten sunlit soil–plant–atmosphere-research (SPAR) chambers were used to study the effects of two [CO2] of low (360 μL L−1) and high (720 μL L−1), and five different day/night temperatures of 20/12, 25/17, 30/22, 35/27 and 40/32 °C. Big bluestem cv. Bonelli seeds were sown in pure, fine sand, in 11 rows at equal spacing and after emergence were thinned to 10 plants per row. At maturity, individual plants were harvested and divided into leaves, stems, panicles and roots. Biomass decreased either above or below the optimum temperature of 30/22 °C. The effect of high [CO2] on biomass accumulation (12–30% increase) was visible at less than optimum temperature (30/22 °C) and absent at two high temperatures. With increase in temperature, irrespective of the [CO2], biomass partitioned to leaves increased (35%) where as that to stems decreased (33%). Panicle weight was 6–7% of biomass at 25/17 °C and fell to 1.6% at 40/32 °C. The biomass partitioned to roots, across the temperatures, was constant for plants grown at low [CO2] but decreased by 7% for those grown at high [CO2]. The decrease in panicle/seed production at two high temperatures (>30/22 °C) might reduce this species population and dominance in tallgrass prairies. The temperature response functions at different [CO2] will be useful to improve the predictive capabilities of dynamic global vegetation models in simulating dynamics of rangelands, where big bluestem is the dominant species. 相似文献
19.
Appropriate resource partitioning to either production of new tillers or growth of individual tillers is a critical factor for increasing rice biomass production and facilitating adaptation to climate change. We examined the contributions of genotypic variation to the tiller number and individual tiller growth of 24 rice cultivars in response to an elevated atmospheric CO2 concentration [CO2] (control + 191 μmol mol−1) and a low air temperature (control minus 4.7 °C) during 56 days of vegetative growth after transplanting. For all genotypes combined, biomass increased by 27% under elevated [CO2] and decreased by 34% at low temperature, with a significant genotype × temperature interaction. The increase caused by elevated [CO2] resulted from increased tiller number, and the decrease caused by low temperature resulted from decreased growth of individual tillers. Despite the different overall responses to elevated [CO2] and low temperature, most of the genotypic variation in biomass at elevated [CO2] and low temperature was explained by the responses of tiller number rather than by individual tiller growth. The genotypes with the highest biomass response to elevated [CO2] had a smaller reduction of biomass under low temperature. These results highlight the greater importance of genotypic variation in tiller number than in individual tiller growth in the response of biomass to environmental change. 相似文献
20.
《Journal of Asia》2014,17(3):349-354
Temperature-dependent development of Spodoptera exigua (Hübner) were evaluated at eight constant temperatures of 12, 15, 20, 25, 30, 33, 34 and 36 °C with a variation of 0.5 °C on sugar beet leaves. No development occurred at 12 °C and 36 °C. Total developmental time varied from 120.50 days at 15 °C to 14.50 days at 33 °C. As temperature increased from 15 °C to 33 °C, developmental rate (1/developmental time) of S. exigua increased but declined at 34 °C. The lower temperature threshold (Tmin) was estimated to be 12.98 °C and 12.45 °C, and the thermal constant (K) was 294.99 DD and 311.76 DD, using the traditional and Ikemoto–Takai linear models, respectively. The slopes of the Ikemoto–Takai linear model for different immature stages were different, violating the assumption of rate isomorphy. Data were fitted to three nonlinear models to predict the developmental rate and estimate the critical temperatures. The Tmin values estimated by Lactin-2 (12.90 °C) and SSI (13.35 °C) were higher than the value estimated by Briere-2 (8.67 °C). The estimated fastest development temperatures (Tfast) by the Briere-2, Lactin-2 and SSI models for overall immature stages development of S. exigua were 33.4 °C, 33.9 °C and 32.4 °C, respectively. The intrinsic optimum temperature (TΦ) estimated from the SSI model was 28.5 °C, in which the probability of enzyme being in its native state is maximal. The upper temperature threshold (Tmax) values estimated by these three nonlinear models varied from 34.00 °C to 34.69 °C. These findings on thermal requirements can be used to predict the occurrence, number of generations and population dynamics of S. exigua. 相似文献