|
| ||
|
|
||
Acclimation
Kinds of Acclimation Terms modified by Acclimation Selected AbstractsACCLIMATION TO VARYING LIGHT QUALITIES: TOWARD THE FUNCTIONAL RELATIONSHIP OF STATE TRANSITIONS AND ADJUSTMENT OF PHOTOSYSTEM STOICHIOMETRYJOURNAL OF PHYCOLOGY, Issue 4 2005Thomas PfannschmidtArticle first published online: 31 AUG 200 No abstract is available for this article. [source] CYANOBACTERIAL ACCLIMATION TO RAPIDLY FLUCTUATING LIGHT IS CONSTRAINED BY INORGANIC CARBON STATUS,JOURNAL OF PHYCOLOGY, Issue 4 2005Tyler D. B. MacKenzie Acclimation to rapidly fluctuating light, simulating shallow aquatic habitats, is altered depending on inorganic carbon (Ci) availability. Under steady light of 50 ,mol photons·m,2·s,1, the growth rate of Synechococcus elongatus PCC7942 was similar in cells grown in high Ci (4 mM) and low Ci (0.02 mM), with induced carbon concentrating mechanisms compensating for low Ci. Growth under fluctuating light of a 1-s period averaging 50 ,mol photons·m,2·s,1 caused a drop in growth rate of 28%±6% in high Ci cells and 38%±8% in low Ci cells. In high Ci cells under fluctuating light, the PSI/PSII ratio increased, the PSII absorption cross-section decreased, and the PSII turnover rate increased in a pattern similar to high-light acclimation. In low Ci cells under fluctuating light, the PSI/PSII ratio decreased, the PSII absorption cross-section decreased, and the PSII turnover remained slow. Electron transport rate was similar in high and low Ci cells but in both was lower under fluctuating than under steady light. After acclimation to a 1-s period fluctuating light, electron transport rate decreased under steady or long-period fluctuating light. We hypothesize that high Ci cells acclimated to exploit the bright phases of the fluctuating light, whereas low Ci cells enlarged their PSII pool to integrate the fluctuating light and dampen the variation of the electron flux into a rate-restricted Ci pool. Light response curves measured under steady light, widely used to predict photosynthetic rates, do not properly predict photosynthetic rates achieved under fluctuating light, and exploitation of fluctuating light is altered by Ci status. [source] INORGANIC CARBON REPLETION DISRUPTS PHOTOSYNTHETIC ACCLIMATION TO LOW TEMPERATURE IN THE CYANOBACTERIUM SYNECHOCOCCUS ELONGATUS,JOURNAL OF PHYCOLOGY, Issue 2 2005Robert A. Burns Acclimation of cyanobacteria to ambient fluctuations in inorganic carbon (Ci) and temperature requires reorganization of the major protein complexes involved in photosynthesis. We grew cultures of the picoplanktonic cyanobacterium Synechococcus elongatus Naegeli across most of its range of tolerable temperatures from 23 to 35°C at both low (<0.1 mM) and high Ci (approximately 4 mM). Over that range of temperatures, the chl-based doubling time did not differ between low and high Ci grown cells but did increase with decreasing temperature. Cells grown at 23°C high Ci showed an elongated morphology, which was not present in 23°C low Ci cells nor at 35°C high and low Ci. Furthermore, 23°C high Ci cells showed premature senescence and death compared with all other treatments. Phycocyanin per cell was greater in high Ci grown cells at all temperatures but showed a characteristic decrease with decreasing temperature. Functional PSII determination showed that 23°C high Ci cells had 1.5 × 105 PSII·cell,1 compared with only 6.9 × 104 PSII·cell,1 for 23°C low Ci. The 35°C high and low Ci cells had 7.7 × 104 and 6.4 × 104 PSII·cell,1, respectively. These data were supported by immunoblot determinations of PsbA content·cell,1. As a result of their high PSII·cell,1, 23°C high Ci cells generated more reductant from PSII than could be accommodated by downstream assimilative metabolism, resulting in early senescence and death of 23°C high Ci cells, probably as a result of the generation of reactive byproducts of electron transport. [source] Uptake kinetics and subcellular compartmentalization of cadmium in acclimated and unacclimated earthworms (Eisenia andrei)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2010Shuo Yu Abstract Acclimation to cadmium (Cd) levels exceeding background concentrations may influence the ability of earthworms to accumulate Cd with minimum adverse effects. In the present study, earthworms (Eisenia andrei) were acclimated by exposure to 20,mg/kg Cd (dry wt) in Webster soil for 28 d. A 224-d bioaccumulation test was subsequently conducted with both acclimated and unacclimated worms exposed in Webster soils spiked with 20,mg/kg and 100,mg/kg Cd (dry wt). Uptake kinetics and subcellular compartmentalization of Cd were examined. Results suggest that acclimated earthworms accumulated more Cd and required a longer time to reach steady state than unacclimated worms. Most of the Cd was present in the metallothionein (MT) fraction. Cadmium in the MT fraction increased approximately linearly with time and required a relatively longer time to reach steady state than Cd in cell debris and granule fractions, which quickly reached steady state. Cadmium in the cell debris fraction is considered potentially toxic, but low steady state concentrations observed in the present study would not suggest the potential for adverse effects. Future use of earthworms in ecological risk assessment should take into consideration pre-exposure histories of the test organisms. A prolonged test period may be required for a comprehensive understanding of Cd uptake kinetics and compartmentalization. Environ. Toxicol. Chem. 2010;29:1568,1574. © 2010 SETAC [source] Acclimation of photosynthesis and respiration to elevated atmospheric CO2 in two Scrub OaksGLOBAL CHANGE BIOLOGY, Issue 4 2002Graham J. Hymus Abstract For two species of oak, we determined whether increasing atmospheric CO2 concentration (Ca) would decrease leaf mitochondrial respiration (R) directly, or indirectly owing to their growth in elevated Ca, or both. In particular, we tested whether acclimatory decreases in leaf-Rubisco content in elevated Ca would decrease R associated with its maintenance. This hypothesis was tested in summer 2000 on sun and shade leaves of Quercus myrtifolia Willd. and Quercus geminata Small. We also measured R on five occasions between summer 1999 and 2000 on leaves of Q. myrtifolia. The oaks were grown in the field for 4 years, in either current ambient or elevated (current ambient + 350 µmol mol,1) Ca, in open-top chambers (OTCs). For Q. myrtifolia, an increase in Ca from 360 to 710 µmol mol,1 had no direct effect on R at any time during the year. In April 1999, R in young Q. myrtifolia leaves was significantly higher in elevated Ca,the only evidence for an indirect effect of growth in elevated Ca. Leaf R was significantly correlated with leaf nitrogen (N) concentration for the sun and shade leaves of both the species of oak. Acclimation of photosynthesis in elevated Ca significantly reduced maximum RuBP-saturated carboxylation capacity (Vc max) for both the sun and shade leaves of only Q. geminata. However, we estimated that only 11,12% of total leaf N was invested in Rubisco; consequently, acclimation in this plant resulted in a small effect on N and an insignificant effect on R. In this study measurements of respiration and photosynthesis were made on material removed from the field; this procedure had no effect on gas exchange properties. The findings of this study were applicable to R expressed either per unit leaf area or unit dry weight, and did not support the hypothesis that elevated Ca decreases R directly, or indirectly owing to acclimatory decreases in Rubisco content. [source] Antagonistic Effects of Hydrogen Peroxide and Glutathione on Acclimation to Excess Excitation Energy in ArabidopsisIUBMB LIFE, Issue 1 2000Barbara Karpinska Abstract The redox status of the quinone B (QB) and plastoquinone (PQ) pools plays a key role in the cellular and systemic signalling processes that control acclimatory responses in plants. In this study, we demonstrate the effects of hydrogen peroxide and glutathione on acclimatory responses controlled by redox events in the proximity of the QB-PQ pools. Our results suggest that the chloroplast is a sink for H2O2 and that, paradoxically, high concentrations of H2O2 in the chloroplast protect the photosynthetic apparatus and the plant cell from photoinhibition and photooxidative damage. Excess glutathione, however, caused an effect antagonistic to that observed for high H2O2. An explanation of this apparent paradox and a hypothetical redox-signalling model are suggested. [source] Contrasts in the hypo-osmoregulatory abilities of a freshwater and an anadromous population of inconnuJOURNAL OF FISH BIOLOGY, Issue 4 2001K. L. Howland Juvenile freshwater and anadromous inconnu Stenodus leucichthys regulated plasma ions following a direct transfer from fresh to brackish water (10,15,), but suffered osmoregulatory collapse with 100% mortality in 48 h when directly transferred to 25, salinity. Acclimation to brackish water for 2 weeks improved hypo-osmoregulatory capacity in both populations, with acclimated fish showing smaller increases in blood plasma ion concentrations, higher Na+ -K+ ATPase activity, and lower mortality than non-acclimated fish following transfer to 25, sea water. Anadromous inconnu maintained pre-treatment plasma ion levels during acclimation, whereas these levels increased during acclimation in freshwater inconnu. Juvenile anadromous inconnu are therefore able to adapt physiologically to sea water of at least 25,, if brackish-water acclimation is available, but freshwater inconnu have diminished saltwater tolerance, relative to the anadromous form. [source] CYANOBACTERIAL ACCLIMATION TO RAPIDLY FLUCTUATING LIGHT IS CONSTRAINED BY INORGANIC CARBON STATUS,JOURNAL OF PHYCOLOGY, Issue 4 2005Tyler D. B. MacKenzie Acclimation to rapidly fluctuating light, simulating shallow aquatic habitats, is altered depending on inorganic carbon (Ci) availability. Under steady light of 50 ,mol photons·m,2·s,1, the growth rate of Synechococcus elongatus PCC7942 was similar in cells grown in high Ci (4 mM) and low Ci (0.02 mM), with induced carbon concentrating mechanisms compensating for low Ci. Growth under fluctuating light of a 1-s period averaging 50 ,mol photons·m,2·s,1 caused a drop in growth rate of 28%±6% in high Ci cells and 38%±8% in low Ci cells. In high Ci cells under fluctuating light, the PSI/PSII ratio increased, the PSII absorption cross-section decreased, and the PSII turnover rate increased in a pattern similar to high-light acclimation. In low Ci cells under fluctuating light, the PSI/PSII ratio decreased, the PSII absorption cross-section decreased, and the PSII turnover remained slow. Electron transport rate was similar in high and low Ci cells but in both was lower under fluctuating than under steady light. After acclimation to a 1-s period fluctuating light, electron transport rate decreased under steady or long-period fluctuating light. We hypothesize that high Ci cells acclimated to exploit the bright phases of the fluctuating light, whereas low Ci cells enlarged their PSII pool to integrate the fluctuating light and dampen the variation of the electron flux into a rate-restricted Ci pool. Light response curves measured under steady light, widely used to predict photosynthetic rates, do not properly predict photosynthetic rates achieved under fluctuating light, and exploitation of fluctuating light is altered by Ci status. [source] INORGANIC CARBON REPLETION DISRUPTS PHOTOSYNTHETIC ACCLIMATION TO LOW TEMPERATURE IN THE CYANOBACTERIUM SYNECHOCOCCUS ELONGATUS,JOURNAL OF PHYCOLOGY, Issue 2 2005Robert A. Burns Acclimation of cyanobacteria to ambient fluctuations in inorganic carbon (Ci) and temperature requires reorganization of the major protein complexes involved in photosynthesis. We grew cultures of the picoplanktonic cyanobacterium Synechococcus elongatus Naegeli across most of its range of tolerable temperatures from 23 to 35°C at both low (<0.1 mM) and high Ci (approximately 4 mM). Over that range of temperatures, the chl-based doubling time did not differ between low and high Ci grown cells but did increase with decreasing temperature. Cells grown at 23°C high Ci showed an elongated morphology, which was not present in 23°C low Ci cells nor at 35°C high and low Ci. Furthermore, 23°C high Ci cells showed premature senescence and death compared with all other treatments. Phycocyanin per cell was greater in high Ci grown cells at all temperatures but showed a characteristic decrease with decreasing temperature. Functional PSII determination showed that 23°C high Ci cells had 1.5 × 105 PSII·cell,1 compared with only 6.9 × 104 PSII·cell,1 for 23°C low Ci. The 35°C high and low Ci cells had 7.7 × 104 and 6.4 × 104 PSII·cell,1, respectively. These data were supported by immunoblot determinations of PsbA content·cell,1. As a result of their high PSII·cell,1, 23°C high Ci cells generated more reductant from PSII than could be accommodated by downstream assimilative metabolism, resulting in early senescence and death of 23°C high Ci cells, probably as a result of the generation of reactive byproducts of electron transport. [source] Submergence-induced leaf acclimation in terrestrial species varying in flooding toleranceNEW PHYTOLOGIST, Issue 2 2007Liesje Mommer Summary ,,Earlier work on the submergence-tolerant species Rumex palustris revealed that leaf anatomical and morphological changes induced by submergence enhance underwater gas exchange considerably. Here, the hypothesis is tested that these plastic responses are typical properties of submergence-tolerant species. ,,Submergence-induced plasticity in leaf mass area (LMA) and leaf, cell wall and cuticle thickness was investigated in nine plant species differing considerably in tolerance to complete submergence. The functionality of the responses for underwater gas exchange was evaluated by recording oxygen partial pressures inside the petioles when plants were submerged. ,,Acclimation to submergence resulted in a decrease in all leaf parameters, including cuticle thickness, in all species irrespective of flooding tolerance. Consequently, internal oxygen partial pressures (pO2) increased significantly in all species until values were close to air saturation. Only in nonacclimated leaves in darkness did intolerant species have a significantly lower pO2 than tolerant species. ,,These results suggest that submergence-induced leaf plasticity, albeit a prerequisite for underwater survival, does not discriminate tolerant from intolerant species. It is hypothesized that these plastic leaf responses may be induced in all species by several signals present during submergence; for example, low LMA may be a response to low photosynthate concentrations and a thin cuticle may be a response to high relative humidity. [source] Cold adaptation in Arctic and Antarctic fungiNEW PHYTOLOGIST, Issue 2 2001Clare H. Robinson Summary Growth and activity at low temperatures and possible physiological and ecological mechanisms underlying survival of fungi isolated from the cold Arctic and Antarctic are reviewed here. Physiological mechanisms conferring cold tolerance in fungi are complex; they include increases in intracellular trehalose and polyol concentrations and unsaturated membrane lipids as well as secretion of antifreeze proteins and enzymes active at low temperatures. A combination of these mechanisms is necessary for the psychrotroph or psychrophile to function. Ecological mechanisms for survival might include cold avoidance; fungal spores may germinate annually in spring and summer, so avoiding the coldest months. Whether spores survive over winter or are dispersed from elsewhere is unknown. There are also few data on persistence of basidiomycete vs microfungal mycelia and on the relationship between low temperatures and the predominance of sterile mycelia in tundra soils. Acclimation of mycelia is a physiological adaptation to subzero temperatures; however, the extent to which this occurs in the natural environment is unclear. Melanin in dark septate hyphae, which predominate in polar soils, could protect hyphae from extreme temperatures and play a significant role in their persistence from year to year. [source] Antioxidative Responses of Two Marine Microalgae During Acclimation to Static and Fluctuating Natural UV RadiationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2009Paul J. Janknegt Photoacclimation properties were investigated in two marine microalgae exposed to four ambient irradiance conditions: static photosynthetically active radiation (PAR: 400,700 nm), static PAR + UVR (280,700 nm), dynamic PAR and dynamic PAR + UVR. High light acclimated cultures of Thalassiosira weissflogii and Dunaliella tertiolecta were exposed outdoors for a maximum of 7 days. Dynamic irradiance was established by computer controlled vertical movement of 2 L bottles in a water filled basin. Immediate (<24 h), short-term (1,3 days) and long-term (4,7 days) photoacclimation was followed for antioxidants (superoxide dismutase, ascorbate peroxidase and glutathione cycling), growth and pigment pools. Changes in UVR sensitivity during photoacclimation were monitored by measuring UVR-induced inhibition of carbon assimilation under standardized UV conditions using an indoor solar simulator. Both species showed immediate antioxidant responses due to their transfer to the outdoor conditions. Furthermore, upon outdoor exposure, carbon assimilation and growth rates were reduced in both species compared with initial conditions; however, these effects were most pronounced in D. tertiolecta. Outdoor UV exposure did not alter antioxidant levels when compared with PAR-only controls in both species. In contrast, growth was significantly affected in the static UVR cultures, concurrent with significantly enhanced UVR resistance. We conclude that antioxidants play a minor role in the reinforcement of natural UVR resistance in T. weissflogii and D. tertiolecta. [source] Respiratory Q10 of marigold (Tagetes patula) in response to long-term temperature differences and its relationship to growth and maintenance respirationPHYSIOLOGIA PLANTARUM, Issue 2 2006Marc W. Van Iersel Acclimation of respiration to temperature is not well understood. To determine whether whole plant respiration responses to long-term temperature treatments can be described using the Q10 concept, the CO2 exchange rate of marigolds (Tagetes patula L. ,Queen Sophia'), grown at 20°C or 30°C, was measured for 62 days. When plants of the same age were compared, plants grown at 20°C consistently had a higher specific respiration (Rspc) than plants grown at 30°C (long-term Q10= 0.71,0.97). This was due to a combination of greater dry mass at 30°C and a decrease in Rspc with increasing mass. When plants of the same dry mass were compared, the long-term Q10 was 1.35,1.55; i.e. Rspc was higher at 30°C than at 20°C. Whole plant respiration could be accurately described by dividing respiration into growth and maintenance components. The maintenance respiration coefficient was higher at 30°C than at 20°C, while the growth respiration coefficient was lower at 30°C, partly because of temperature-dependent changes in plant composition. These results suggest difficulties with interpreting temperature effects on whole plant respiration, because conclusions depend greatly on whether plants of the same age or mass are compared. These difficulties can be minimized by describing whole plant respiration on the basis of growth and maintenance components. [source] Photosynthetic Acclimation to Simultaneous and Interacting Environmental Stresses Along Natural Light Gradients: Optimality and ConstraintsPLANT BIOLOGY, Issue 3 2004ü. Niinemets Abstract: There is a strong natural light gradient from the top to the bottom in plant canopies and along gap-understorey continua. Leaf structure and photosynthetic capacities change close to proportionally along these gradients, leading to maximisation of whole canopy photosynthesis. However, other environmental factors also vary within the light gradients in a correlative manner. Specifically, the leaves exposed to higher irradiance suffer from more severe heat, water, and photoinhibition stresses. Research in tree canopies and across gap-understorey gradients demonstrates that plants have a large potential to acclimate to interacting environmental limitations. The optimum temperature for photosynthetic electron transport increases with increasing growth irradiance in the canopy, improving the resistance of photosynthetic apparatus to heat stress. Stomatal constraints on photosynthesis are also larger at higher irradiance because the leaves at greater evaporative demands regulate water use more efficiently. Furthermore, upper canopy leaves are more rigid and have lower leaf osmotic potentials to improve water extraction from drying soil. The current review highlights that such an array of complex interactions significantly modifies the potential and realized whole canopy photosynthetic productivity, but also that the interactive effects cannot be simply predicted as composites of additive partial environmental stresses. We hypothesize that plant photosynthetic capacities deviate from the theoretical optimum values because of the interacting stresses in plant canopies and evolutionary trade-offs between leaf- and canopy-level plastic adjustments in light capture and use. [source] Long-term growth of soybean at elevated [CO2] does not cause acclimation of stomatal conductance under fully open-air conditionsPLANT CELL & ENVIRONMENT, Issue 9 2006ANDREW D. B. LEAKEY ABSTRACT Accurately predicting plant function and global biogeochemical cycles later in this century will be complicated if stomatal conductance (gs) acclimates to growth at elevated [CO2], in the sense of a long-term alteration of the response of gs to [CO2], humidity (h) and/or photosynthetic rate (A). If so, photosynthetic and stomatal models will require parameterization at each growth [CO2] of interest. Photosynthetic acclimation to long-term growth at elevated [CO2] occurs frequently. Acclimation of gs has rarely been examined, even though stomatal density commonly changes with growth [CO2]. Soybean was grown under field conditions at ambient [CO2] (378 µmol mol,1) and elevated [CO2] (552 µmol mol,1) using free-air [CO2] enrichment (FACE). This study tested for stomatal acclimation by parameterizing and validating the widely used Ball et al. model (1987, Progress in Photosynthesis Research, vol IV, 221,224) with measurements of leaf gas exchange. The dependence of gs on A, h and [CO2] at the leaf surface was unaltered by long-term growth at elevated [CO2]. This suggests that the commonly observed decrease in gs under elevated [CO2] is due entirely to the direct instantaneous effect of [CO2] on gs and that there is no longer-term acclimation of gs independent of photosynthetic acclimation. The model accurately predicted gs for soybean growing under ambient and elevated [CO2] in the field. Model parameters under ambient and elevated [CO2] were indistinguishable, demonstrating that stomatal function under ambient and elevated [CO2] could be modelled without the need for parameterization at each growth [CO2]. [source] Relative enhancement of photosynthesis and growth at elevated CO2 is greater under sunflecks than uniform irradiance in a tropical rain forest tree seedlingPLANT CELL & ENVIRONMENT, Issue 12 2002A. D. B. LEAKEY Abstract The survivorship of dipterocarp seedlings in the deeply shaded understorey of South-east Asian rain forests is limited by their ability to maintain a positive carbon balance. Photosynthesis during sunflecks is an important component of carbon gain. To investigate the effect of elevated CO2 upon photosynthesis and growth under sunflecks, seedlings of Shorealeprosula were grown in controlled environment conditions at ambient or elevated CO2. Equal total daily photon flux density (PFD) (,7·7 mol m,2 d,1) was supplied as either uniform irradiance (,170 µmol m,2 s,1) or shade/fleck sequences (,30 µmol m,2 s,1/,525 µmol m,2 s,1). Photosynthesis and growth were enhanced by elevated CO2 treatments but lower under flecked irradiance treatments. Acclimation of photosynthetic capacity occurred in response to elevated CO2 but not flecked irradiance. Importantly, the relative enhancement effects of elevated CO2 were greater under sunflecks (growth 60%, carbon gain 89%) compared with uniform irradiance (growth 25%, carbon gain 59%). This was driven by two factors: (1) greater efficiency of dynamic photosynthesis (photosynthetic induction gain and loss, post-irradiance gas exchange); and (2) photosynthetic enhancement being greatest at very low PFD. This allowed improved carbon gain during both clusters of lightflecks (73%) and intervening periods of deep shade (99%). The relatively greater enhancement of growth and photosynthesis at elevated CO2 under sunflecks has important potential consequences for seedling regeneration processes and hence forest structure and composition. [source] Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit areaPLANT CELL & ENVIRONMENT, Issue 3 2002P. Meir Abstract The observation of acclimation in leaf photosynthetic capacity to differences in growth irradiance has been widely used as support for a hypothesis that enables a simplification of some soil-vegetation-atmosphere transfer (SVAT) photosynthesis models. The acclimation hypothesis requires that relative leaf nitrogen concentration declines with relative irradiance from the top of a canopy to the bottom, in 1 : 1 proportion. In combination with a light transmission model it enables a simple estimate of the vertical profile in leaf nitrogen concentration (which is assumed to determine maximum carboxylation capacity), and in combination with estimates of the fraction of absorbed radiation it also leads to simple ,big-leaf' analytical solutions for canopy photosynthesis. We tested how forests deviate from this condition in five tree canopies, including four broadleaf stands, and one needle-leaf stand: a mixed-species tropical rain forest, oak (Quercus petraea (Matt.) Liebl), birch (Betula pendula Roth), beech (Fagus sylvatica L.) and Sitka spruce (Picea sitchensis (Bong.) Carr). Each canopy was studied when fully developed (mid-to-late summer for temperate stands). Irradiance (Q, µmol m,2 s,1) was measured for 20 d using quantum sensors placed throughout the vertical canopy profile. Measurements were made to obtain parameters from leaves adjacent to the radiation sensors: maximum carboxylation and electron transfer capacity (Va, Ja, µmol m,2 s,1), day respiration (Rda, µmol m,2 s,1), leaf nitrogen concentration (Nm, mg g,1) and leaf mass per unit area (La, g m,2). Relative to upper-canopy values, Va declined linearly in 1 : 1 proportion with Na. Relative Va also declined linearly with relative Q, but with a significant intercept at zero irradiance (P < 0·01). This intercept was strongly related to La of the lowest leaves in each canopy (P < 0·01, r2 = 0·98, n= 5). For each canopy, daily lnQ was also linearly related with lnVa(P < 0·05), and the intercept was correlated with the value for photosynthetic capacity per unit nitrogen (PUN: Va/Na, µmol g,1 s,1) of the lowest leaves in each canopy (P < 0·05). Va was linearly related with La and Na(P < 0·01), but the slope of the Va : Na relationship varied widely among sites. Hence, whilst there was a unique Va : Na ratio in each stand, acclimation in Va to Q varied predictably with La of the lowest leaves in each canopy. The specific leaf area, Lm(cm2 g,1), of the canopy-bottom foliage was also found to predict carboxylation capacity (expressed on a mass basis; Vm, µmol g,1 s,1) at all sites (P < 0·01). These results invalidate the hypothesis of full acclimation to irradiance, but suggest that La and Lm of the most light-limited leaves in a canopy are widely applicable indicators of the distribution of photosynthetic capacity with height in forests. [source] Acclimation of tropical tree seedlings to excessive light in simulated tree-fall gapsPLANT CELL & ENVIRONMENT, Issue 12 2001G. H. Krause Abstract Acclimation to periodic high-light stress was studied in tree seedlings from a neotropical forest. Seedlings of several pioneer and late-succession species were cultivated under simulated tree-fall gap conditions; they were placed under frames covered with shade cloth with apertures of different widths that permitted defined periods of daily leaf exposure to direct sunlight. During direct sun exposure, all plants exhibited a marked reversible decline in potential photosystem II (PSII) efficiency, determined by means of the ratio of variable to maximum Chl a fluorescence (Fv/Fm). The decline in Fv/Fm under full sunlight was much stronger in late-succession than in pioneer species. For each gap size, all species exhibited a similar degree of de-epoxidation of violaxanthin in direct sunlight and similar pool sizes of xanthophyll cycle pigments. Pool sizes increased with increasing gap size. Pioneer plants possessed high levels of , -carotene that also increased with gap size, whereas , -carotene decreased. In contrast to late-succession plants, pioneer plants were capable of adjusting their Chl a/b ratio to a high value in wide gaps. The content of extractable UV-B-absorbing compounds was highest in the plants acclimated to large gaps and did not depend on the successional status of the plants. The results demonstrate a better performance of pioneer species under high-light conditions as compared with late-succession plants, manifested by reduced photoinhibition of PSII in pioneer species. This was not related to increased pool size and turnover of xanthophyll cycle pigments, nor to higher contents of UV-B-absorbing substances. High , -carotene levels and increased Chl a/b ratios, i.e. reduced size of the Chl a and b binding antennae, may contribute to photoprotection in pioneer species. [source] UV-B-induced DNA damage and expression of defence genes under UV-B stress: tissue-specific molecular marker analysis in leavesPLANT CELL & ENVIRONMENT, Issue 9 2001G. Kalbin Abstract The aim of this study was to investigate the regulatory effect of ultraviolet-B (UV-B) radiation on a number of key stress response genes found in the epidermis and mesophyll of Pisum sativum L., Argenteum mutant. This mutant was chosen for the ease with which the entire epidermis can be removed from the mesophyll tissue. An additional goal was to explore the potential modifying effect of pre-acclimation of plants to UV-B radiation prior to exposure by UV-B during treatment. Results showed that mRNA accumulation was similar during acute short-term UV-B exposure for chalcone synthase (Chs) and short-chain alcohol dehydrogenase (SadA) in both epidermis and mesophyll. In contrast, the mRNA levels differed considerably between tissues for phenylalanine ammonia lyase, chalcone isomerase and lipid transfer protein. After 24 h incubation in visible light after cessation of UV-B exposure, the regulation of mRNA levels also differed between Chs and SadA, the former showing no expression in the epidermis and the latter none in the mesophyll. Acclimation to low UV-B levels before acute exposures resulted in delayed induction of Chs and SadA. Measurements of UV-B-induced cyclobutane pyrimidine dimers (CPDs) showed a greater formation in epidermis than in mesophyll. In addition, acclimation at low UV-B levels resulted in significantly higher basal levels of CPDs than in non-acclimated plants in both mesophyll and epidermis and also in increased damage in concomitant acute exposures. The lack of correlation between the number of CPDs and levels of transcripts for defence genes, indicates that DNA damage does not control transcription of these genes. [source] Strategies providing success in a variable habitat: III.PLANT CELL & ENVIRONMENT, Issue 8 2001Dynamic control of photosynthesis in Cladophora glomerata Abstract Diurnal patterns of photosynthesis were studied in July and April populations of Cladophora glomerata (L.) Kütz. from open and from shaded sites. Summer samples exposed to full sunlight showed decreased efficiency of open photosystem II at noon, and only slight differences were found between samples that had grown at open or at shaded sites. Electron transport rate was limited at highest fluence rates in shade plants, and non-photochemical quenching (NPQ) revealed faster regulation in samples from open sites. Daily course of de-epoxidation was not linearly correlated with the course of NPQ. The comparison of samples from open and from shaded sites revealed a higher capacity of thermal energy dissipation and an increase in the total amount of xanthophyll-cycle pigments (21%) in samples from open sites. In April, down-regulation of the efficiency of open photosystem II was related to lower water temperature, and hence, increased excitation pressure. In April the pool size of xanthophyll-cycle pigments was increased by 21% in comparison with summer and suggested higher levels of thermal energy dissipation via de-epoxidized xanthophylls. In both, summer and spring the amount of xanthophyll-cycle pigments was 20% higher in samples from open sites. Acclimation of C. glomerata to growth light conditions was further shown by experimental induction of NPQ, indicating NPQ increases of 23%, and increases of 77% in the reversible component of NPQ in open site samples. The effect of temperature on photosynthetic rate was non-linear, and different optimum temperatures of electron transport rate and oxygen evolution were exhibited. [source] Acclimation of snow gum (Eucalyptus pauciflora) leaf respiration to seasonal and diurnal variations in temperature: the importance of changes in the capacity and temperature sensitivity of respirationPLANT CELL & ENVIRONMENT, Issue 1 2000O. K. Atkin ABSTRACT We investigated the relationship between daily and seasonal temperature variation and dark respiratory CO2 release by leaves of snow gum (Eucalyptus pauciflora Sieb. ex Spreng) that were grown in their natural habitat or under controlled-environment conditions. The open grassland field site in SE Australia was characterized by large seasonal and diurnal changes in air temperature. On each measurement day, leaf respiration rates in darkness were measured in situ at 2,3 h intervals over a 24 h period, with measurements being conducted at the ambient leaf temperature. The rate of respiration at a set measuring temperature (i.e. apparent ,respiratory capacity') was greater in seedlings grown under low average daily temperatures (i.e. acclimation occurred), both in the field and under controlled-environment conditions. The sensitivity of leaf respiration to diurnal changes in temperature (i.e. the Q10 of leaf respiration) exhibited little seasonal variation over much of the year. However, Q10 values were significantly greater on cold winter days (i.e. when daily average and minimum air temperatures were below 6° and ,1 °C, respectively). These differences in Q10 values were not due to bias arizing from the contrasting daily temperature amplitudes in winter and summer, as the Q10 of leaf respiration was constant over a wide temperature range in short-term experiments. Due to the higher Q10 values in winter, there was less difference between winter and summer leaf respiration rates measured at 5 °C than at 25 °C. The net result of these changes was that there was relatively little difference in total daily leaf respiratory CO2 release per unit leaf dry mass in winter and summer. Under controlled-environment conditions, acclimation of respiration to growth temperature occurred in as little as 1,3 d. Acclimation was associated with a change in the concentration of soluble sugars under controlled conditions, but not in the field. Our data suggest that acclimation in the field may be associated with the onset of cold-induced photo-inhibition. We conclude that cold-acclimation of dark respiration in snow gum leaves is characterized by changes in both the temperature sensitivity and apparent ,capacity' of the respiratory apparatus, and that such changes will have an important impact on the carbon economy of snow gum plants. [source] Banana (Musa spp.) as a model to study the meristem proteome: Acclimation to osmotic stressPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 1 2007Sebastien C. Carpentier Abstract Banana (Musa spp.) multiple shoot meristems are an excellent model to study the meristem proteome. Using a 2-DE protocol developed for small amounts of tissue and MS-based cross species polypeptide identification, we have revealed the meristem proteome and investigated the influence of sucrose-mediated osmotic stress in a dehydration-tolerant variety. Proteins that were significantly up- or down-regulated due to the high-sucrose treatment were classified using non-parametric univariate statistics. Our results suggest that the maintenance of an osmoprotective intracellular sucrose concentration, the enhanced expression of particular genes of the energy-conserving glycolysis and the conservation of the cell wall integrity are essential to maintain homeostasis, to acclimate and to survive dehydration. By comparing the dehydration-tolerant variety with a dehydration-sensitive variety, we were able to distinguish several genotype-specific proteins (isoforms), and could associate the dehydration-tolerant variety with proteins involved in energy metabolism (e.g., phosphoglycerate kinase, phosphoglucomutase, UDP-glucose pyrophosphorylase) and proteins that are associated with stress adaptation (e.g., OSR40-like protein, abscisic stress ripening protein-like protein). This work shows that proteome analysis can be used successfully to perform quantitative difference analysis and to characterize genetic variations in a recalcitrant crop. [source] CO2 limitation induces specific redox-dependent protein phosphorylation in Chlamydomonas reinhardtiiPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 9 2006Maria V. Turkina Abstract Acclimation of the green alga Chlamydomonas reinhardtii to limiting environmental CO2 induced specific protein phosphorylation at the surface of photosynthetic thylakoid membranes. Four phosphopeptides were identified and sequenced by nanospray quadrupole TOF MS from the cells acclimating to limiting CO2. One phosphopeptide originated from a protein that has not been annotated. We found that this unknown expressed protein (UEP) was encoded in the genome of C.,reinhardtii. Three other phosphorylated peptides belonged to Lci5 protein encoded by the low-CO2 -inducible gene,5 (lci5). The phosphorylation sites were mapped in the tandem repeats of Lci5 ensuring phosphorylation of four serine and three threonine residues in the protein. Immunoblotting with Lci5-specific antibodies revealed that Lci5 was localized in chloroplast and confined to the stromal side of the thylakoid membranes. Phosphorylation of Lci5 and UEP occurred strictly at limiting CO2; it required reduction of electron carriers in the thylakoid membrane, but was not induced by light. Both proteins were phosphorylated in the low-CO2 -exposed algal mutant deficient in the light-activated protein kinase,Stt7. Phosphorylation of previously unknown basic proteins UEP and Lci5 by specific redox-dependent protein kinase(s) in the photosynthetic membranes reveals the early response of green algae to limitation in the environmental inorganic carbon. [source] Acclimation of photosynthesis to elevated CO2 in onion (Allium cepa) grown at a range of temperaturesANNALS OF APPLIED BIOLOGY, Issue 1 2004T R WHEELER Summary Onion (Allium cepa) was grown in the field within temperature gradient tunnels (providing about -2.5°C to +2.5°C from outside temperatures) maintained at either 374 or 532 ,mol mol,1 CO2. Plant leaf area was determined non-destructively at 7 day intervals until the time of bulbing in 12 combinations of temperature and CO2 concentration. Gas exchange was measured in each plot at the time of bulbing, and the carbohydrate content of the leaf (source) and bulb (sink) was determined. Maximum rate of leaf area expansion increased with mean temperature. Leaf area duration and maximum rate of leaf area expansion were not significantly affected by CO2. The light-saturated rates of leaf photosynthesis (Asat) were greater in plants grown at normal than at elevated CO2 concentrations at the same measurement CO2 concentration. Acclimation of photosynthesis decreased with an increase in growth temperature, and with an increase in leaf nitrogen content at elevated CO2. The ratio of intercellular to atmospheric CO2 (C1/C3 ratio) was 7.4% less for plants grown at elevated compared with normal CO2. Asat in plants grown at elevated CO2 was less than in plants grown at normal CO2 when compared at the same C1. Hence, acclimation of photosynthesis was due both to stomatal acclimation and to limitations to biochemical CO2 fixation. Carbohydrate content of the onion bulbs was greater at elevated than at normal CO2. In contrast, carbohydrate content was less at elevated compared with normal CO2 in the leaf sections in which CO2 exchange was measured at the same developmental stage. Therefore, acclimation of photosynthesis in fully expanded onion leaves was detected despite the absence of localised carbohydrate accumulation in these field-grown crops. [source] Animal performance and stress: responses and tolerance limits at different levels of biological organisationBIOLOGICAL REVIEWS, Issue 2 2009Karin S. Kassahn ABSTRACT Recent advances in molecular biology and the use of DNA microarrays for gene expression profiling are providing new insights into the animal stress response, particularly the effects of stress on gene regulation. However, interpretation of the complex transcriptional changes that occur during stress still poses many challenges because the relationship between changes at the transcriptional level and other levels of biological organisation is not well understood. To confront these challenges, a conceptual model linking physiological and transcriptional responses to stress would be helpful. Here, we provide the basis for one such model by synthesising data from organismal, endocrine, cellular, molecular, and genomic studies. We show using available examples from ectothermic vertebrates that reduced oxygen levels and oxidative stress are common to many stress conditions and that the responses to different types of stress, such as environmental, handling and confinement stress, often converge at the challenge of dealing with oxygen imbalance and oxidative stress. As a result, a common set of stress responses exists that is largely independent of the type of stressor applied. These common responses include the repair of DNA and protein damage, cell cycle arrest or apoptosis, changes in cellular metabolism that reflect the transition from a state of cellular growth to one of cellular repair, the release of stress hormones, changes in mitochondrial densities and properties, changes in oxygen transport capacities and changes in cardio-respiratory function. Changes at the transcriptional level recapitulate these common responses, with many stress-responsive genes functioning in cell cycle control, regulation of transcription, protein turnover, metabolism, and cellular repair. These common transcriptional responses to stress appear coordinated by only a limited number of stress-inducible and redox-sensitive transcription factors and signal transduction pathways, such as the immediate early genes c-fos and c-jun, the transcription factors NF,B and HIF - 1,, and the JNK and p38 kinase signalling pathways. As an example of environmental stress responses, we present temperature response curves at organismal, cellular and molecular levels. Acclimation and physiological adjustments that can shift the threshold temperatures for the onset of these responses are discussed and include, for example, adjustments of the oxygen delivery system, the heat shock response, cellular repair system, and transcriptome. Ultimately, however, an organism's ability to cope with environmental change is largely determined by its ability to maintain aerobic scope and to prevent loss in performance. These systemic constraints can determine an organism's long-term survival well before cellular and molecular functions are disturbed. The conceptual model we propose here discusses some of the crosslinks between responses at different levels of biological organisation and the central role of oxygen balance and oxidative stress in eliciting these responses with the aim to help the interpretation of environmental genomic data in the context of organismal function and performance. [source] Microbial Hydrogen Production with Immobilized Sewage SludgeBIOTECHNOLOGY PROGRESS, Issue 5 2002Shu-Yii Wu Municipal sewage sludge was immobilized to produce hydrogen gas under anaerobic conditions. Cell immobilization was essentially achieved by gel entrapment approaches, which were physically or chemically modified by addition of activated carbon (AC), polyurethane (PU), and acrylic latex plus silicone (ALSC). The performance of hydrogen fermentation with a variety of immobilized-cell systems was assessed to identify the optimal type of immobilized cells for practical uses. With sucrose as the limiting carbon source, hydrogen production was more efficient with the immobilized-cell system than with the suspended-cell system, and in both cases the predominant soluble metabolites were butyric acid and acetic acid. Addition of activated carbon into alginate gel (denoted as CA/AC cells) enhanced the hydrogen production rate ( vH2) and substrate-based yield ( YH2/sucrose) by 70% and 52%, respectively, over the conventional alginate-immobilized cells. Further supplementation of polyurethane or acrylic latex/silicone increased the mechanical strength and operation stability of the immobilized cells but caused a decrease in the hydrogen production rate. Kinetic studies show that the dependence of specific hydrogen production rates on the concentration of limiting substrate (sucrose) can be described by Michaelis-Menten model with good agreement. The kinetic analysis suggests that CA/AC cells may contain higher concentration of active biocatalysts for hydrogen production, while PU and ALSC cells had better affinity to the substrate. Acclimation of the immobilized cells led to a remarkable enhancement in vH2 with a 25-fold increase for CA/AC and ca. 10- to 15-fold increases for PU and ALSC cells. However, the ALSC cells were found to have better durability than PU and CA/AC cells as they allowed stable hydrogen production for over 24 repeated runs. [source] Intergenerational acclimation in aphid overwinteringECOLOGICAL ENTOMOLOGY, Issue 1 2008S. J. POWELL Abstract 1.,When first instar nymphs and adults of the grain aphid Sitobion avenae (Fabricius) (Hemiptera: Aphidiae) were maintained in long-term cultures (>6 months) at 20 °C and 10 °C, the LT50 decreased from ,8 and ,8.8 °C to ,16.0 and ,13.5 °C, respectively. 2.,When aphids from the 20 °C culture were transferred to 10 °C, there was a progressive increase in cold tolerance through three successive generations. Transfer of newly moulted pre-reproductive adults reared at 10 °C for three generations back to 20 °C resulted in a rapid loss of cold hardiness in their nymphal offspring. 3.,In all generations reared at 10 °C, first born nymphs were more cold hardy than those born later in the birth sequence. The LT50 of nymphs produced on the first day of reproduction in the first, second and third generations maintained at 10 °C were ,14.8, ,17.0 and ,16.6 °C, respectively. Thereafter, nymphal cold hardiness decreased over the subsequent 14 days of reproduction in each generation at 10 °C with mean LT50 values of ,10.3, ,12.6 and ,14.8 °C, respectively. By contrast, the cold tolerance of first born nymphs of aphids reared continuously at 20 °C did not differ in comparison with later born siblings. The LT50 of adult aphids was also unaffected by ageing. 4.,The ecological relevance of these findings is discussed in relation to the overwintering survival of aphids such as S. avenae. [source] Cover Picture: Electrophoresis 17'09ELECTROPHORESIS, Issue 17 2009Article first published online: 26 AUG 200 Issue no. 17 is an Emphasis Issue with 10 articles on various aspects of "Proteins and Proteomics" while the remaining 10 articles are arranged into 3 different parts including "Chip Technology", "Nucleic Acids", and "Methodologies, Assays and Applications." Selected articles are: Proteomic analysis of Oenococcus oeni freeze-dried culture to assess the importance of cell acclimation to conduct malolactic fermentation in wine ((10.1002/elps.200900228)) Complete sequencing and oxidative modification of Mn-SOD (SOD2) in medulloblastoma cells ((10.1002/elps.200900168)) Differentiation of Staphylococcus aureus strains by capillary electrophoresis, zeta potential and coagulase gene polymorphism ((10.1002/elps.200900186)) [source] Acclimation Strategy of a Biohydrogen Producing Population in a Continuous-Flow Reactor with Carbohydrate FermentationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2006Q. Ren Abstract Poor startup of biological hydrogen production systems can cause an ineffective hydrogen production rate and poor biomass growth at a high hydraulic retention time (HRT), or cause a prolonged period of acclimation. In this paper a new startup strategy was developed in order to improve the enrichment of the hydrogen-producing population and the efficiency of hydrogen production. A continuously-stirred tank reactor (CSTR) and molasses were used to evaluate the hydrogen productivity of the sewage sludge microflora at a temperature of 35,°C. The experimental results indicated that the feed to microorganism ratio (F/M ratio) was a key parameter for the enrichment of hydrogen producing sludge in a continuous-flow reactor. When the initial biomass was inoculated with 6.24,g of volatile suspended solids (VSS)/L, an HRT of 6,h, an initial organic loading rate (OLR) of 7.0,kg chemical oxygen demand (COD)/(m3,×,d) and an feed to microorganism ratio (F/M) ratio of about 2,3,g COD/(g of volatile suspended solids (VSS) per day) were maintained during startup. Under these conditions, a hydrogen producing population at an equilibrium state could be established within 30,days. The main liquid fermentation products were acetate and ethanol. Biogas was composed of H2 and CO2. The hydrogen content in the biogas amounted to 47.5,%. The average hydrogen yield was 2.01,mol/mol hexose consumed. It was also observed that a special hydrogen producing population was formed when this startup strategy was used. It is supposed that the population may have had some special metabolic pathways to produce hydrogen along with ethanol as the main fermentation products. [source] Cold hardiness of diapausing and non-diapausing pupae of the European grapevine moth, Lobesia botranaENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2005Stefanos S. Andreadis Abstract Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) is a key pest of grapes in Europe. It overwinters as a pupa in the bark crevices of the plant. Supercooling point (SCP) and low temperature survival was investigated in the laboratory and was determined using a cool bath and a 1 °C min,1 cooling rate. Freezing was fatal both to diapausing and non-diapausing pupae. SCP was significantly lower in diapausing male (,24.8 °C) and female (,24.5 °C) pupae than in non-diapausing ones (,22.7 and ,22.5 °C, respectively). Sex had no influence on SCP both for diapausing and non-diapausing pupae. Supercooling was also not affected by acclimation. However, acclimation did improve survival of diapausing pupae at temperatures above the SCP. Survival increased as acclimation period increased and the influence was more profound at the lower temperatures examined. Diapausing pupae could withstand lower temperatures than non-diapausing ones and lethal temperature was significantly lower than for non-diapausing pupae. Freezing injury above the SCP has been well documented for both physiological stages of L. botrana pupae. Our findings suggest a diapause-related cold hardiness for L. botrana and given its cold hardiness ability, winter mortality due to low temperatures is not expected to occur, especially in southern Europe. [source] | ||||||||||||||||||||||||||||||||||