A field study of photosynthetic temperature acclimation in Carex eleocharis Bailey

Abstract. Seasonal patterns in photosynthetic temperature acclimation and growth were investigated in the sedge, Carex eleocharis Bailey, a species which has demonstrated a marked capacity for shifts in the photosynthetic temperature optimum in previous growth chamber studies. The seasonal production of new leaves was 90% complete by the earliest study date, June 3. Shifts in the photosynthetic temperature optimum of 10°C (from 15 to 25°C) were observed during the months of June and July. These results indicate that in situ acclimatory adjustments in C. eleocharis occur in existing leaf tissue, rather than new leaves which are produced as the season progresses. Despite the 10°C increase in the temperature optimum, mean mid-day leaf temperatures were higher than the optimum throughout the summer. A broad temperature response appeared to be more important than the acclimation adjustments in maintaining near-maximum photosynthesis rates during the mid-day period. Seasonal shifts in the photosynthetic temperature optimum were not as great as those previously observed in growth chamber studies. This discrepancy arises because of the capacity for growth chamber grown plants to produce new leaves with temperature response characteristics closely tuned to the growth temperature regime. In field-grown plants the production of 90% of the leaves during the cool portion of the season places limitations on the potential for acclimation to the warmer midsummer temperatures.     

Effects of day and night temperature and temperature variation on photosynthetic characteristics

Net photosynthetic rates and mesophyll conductances were measured under standardized conditions for leaves of two C₃ and one C₄ annual species grown at temperatures of 20 to 32°C. Plants were grown with varying day and night temperatures, and also at constant temperatures equal to all the day and night temperatures used. Plants were grown with 8, 12, and 16 hours of light per day. This design allowed determination of whether photosynthetic characteristics were best correlated with day, night, mean, or time-weighted mean temperatures, The results showed that for Glycine max (L.) Merr. (C₃) night temperature was most important in determining photosynthetic characteristics, while in Helianthus annuus L. (C₃) and Amaranthus hypochondriacus L. (C₄) the time-weighted mean temperature was most important. The results for all species were consistent with the hypothesis that development of photosynthetic characteristics is related to a balance between the rate of leaf expansion and the rate of photosynthesis under the growth conditions.     

An analysis of photosynthetic response and adaptation to temperature in higher plants: temperature acclimation in the desert evergreen Nerium oleander L*

Abstract. Factors underlying the process of photosynthetic acclimation to temperature were investigated for the shrub Nerium oleander L. Ramets of a single clone were grown under day/night temperature regimes of 20°C/15°C or 45°C/32°C. Plants grown at the lower temperature regime possessed rates of photosynthesis twice that of the high-temperature grown plants when CO₂ fixation was measured at 20°C. In contrast, the plants grown at the high-temperature regime had twice the rate of CO₂ fixation of the 20°C/l 5°C-grown plants at a measurement temperature of 45° C. It was determined that the ability to acclimate to changes in temperature regime was present in fully mature leaves. A reciprocal transfer of plants between the two growth regimes resulted in the appearance of the CO₂ fixation characteristics appropriate to the new growth temperature after 12–14d. The response of CO₂ fixation to light, temperature, and CO₂ partial pressure and the temperature responses of soluble and membrane-bound photosynthetic enzyme systems were analysed to determine which components might be responsible for the superior photosynthetic performance of the 20°C/I5°C-grown plants at 20°C, and the enhanced high-temperature stability of the 45°C/32°C plants. The measured photosynthetic capacity of the 20°C/15°C plants could not be attributed to gross morphological, stomatal, or other physical changes, or to a general increase in the concentration of components of the photosynthetic process. Only a single enzyme, Fru-P₂ phosphatase, was affected to an extent similar to that of photosynthesis. The enhanced thermal stability of the 45°C/32°C plants may be attributed primarily to an enhanced stability of the chloroplast membrane-bound enzymatic activities and the stability of the photosynthetic carbon metabolism enzymes which require lighl for activation.     

Seasonal patterns of photosynthetic response and acclimation to elevated carbon dioxide in field-grown strawberry

Strawberry (Fragaria × ananassa) plants were grown in field plots at the current ambient [CO₂], and at ambient + 300 and ambient + 600 μmol mol⁻¹ [CO₂]. Approximately weekly measurements were made of single leaf gas exchange of upper canopy leaves from early spring through fall of two years, in order to determine the temperature dependence of the stimulation of photosynthesis by elevated [CO₂], whether growth at elevated [CO₂] resulted in acclimation of photosynthesis, and whether any photosynthetic acclimation was reduced when fruiting created additional demand for the products of photosynthesis. Stimulation of photosynthetic CO₂ assimilation by short-term increases in [CO₂] increased strongly with measurement temperature. The stimulation exceeded that predicted from the kinetic characteristics of ribulose-1,5-bisphosphate carboxylase at all temperatures. Acclimation of photosynthesis to growth at elevated [CO₂] was evident from early spring through summer, including the fruiting period in early summer, with lower rates under standard measurement conditions in plants grown at elevated [CO₂]. The degree of acclimation increased with growth [CO₂]. However, there were no significant differences between [CO₂] treatments in total nitrogen per leaf area, and photosynthetic acclimation was reversed one day after switching the [CO₂] treatments. Tests showed that acclimation did not result from a limitation of photosynthesis by triose phosphate utilization rate at elevated [CO₂]. Photosynthetic acclimation was not evident during dry periods in midsummer, when the elevated [CO₂] treatments conserved soil water and photosynthesis declined more at ambient than at elevated [CO₂]. Acclimation was also not evident during the fall, when plants were vegetative, despite wet conditions and continued higher leaf starch content at elevated [CO₂]. Stomatal conductance responded little to short-term changes in [CO₂] except during drought, and changed in parallel with photosynthetic acclimation through the seasons in response to the long-term [CO₂] treatments. The data do not support the hypothesis that source-sink balance controls the seasonal occurrence of photosynthetic acclimation to elevated [CO₂] in this species. This revised version was published online in June 2006 with corrections to the Cover Date.     

The vertical distribution of nitrogen and photosynthetic activity at different plant densities in Carex acutiformis

Shoots of the monocotyledonous perennial Carex acutiformis were grown in open (28 shoots m⁻²) and dense stands (280 shoots m⁻²). For fully grown stands the distribution of relative PPFD and leaf nitrogen per unit leaf area over canopy depth was determined. Light response of photosynthesis was measured on leaf segments sampled at various heights in the stands. Relations between parameters of these curves and leaf nitrogen were investigated. Simulations showed that in the open stand daily canopy photosynthesis was not affected by nitrogen redistribution in the canopy. For the dense stand however, a uniform nitrogen distribution would lead to only 73% of the maximum net carbon gain by the stand under optimal nitrogen distribution. The actual canopy photosynthesis was only 7% less than this theoretical maximum; the actual nitrogen distribution of the dense stand clearly tended to the optimal distribution. The vertical pattern of the nitrogen distribution was to a large extent determined by the minimum leaf nitrogen content. The relatively high minimum leaf nitrogen content found for Carex leaves may perhaps be necessary to maintain the physiological function of the basal parts of the leaves.     

A mechanistic evaluation of photosynthetic acclimation at elevated CO2

Plants grown at elevated pCO₂ often fail to sustain the initial stimulation of net CO₂ uptake rate (A). This reduced, acclimated, stimulation of A often occurs concomitantly with a reduction in the maximum carboxylation velocity (V_c,max) of Rubisco. To investigate this relationship we used the Farquhar model of C₃ photosynthesis to predict the minimum V_c,max capable of supporting the acclimated stimulation in A observed at elevated pCO₂. For a wide range of species grown at elevated pCO₂ under contrasting conditions we found a strong correlation between observed and predicted values of V_c,max. This exercise mechanistically and quantitatively demonstrated that the observed acclimated stimulation of A and the simultaneous decrease in V_c,max observed at elevated pCO₂ is mechanistically consistent. With the exception of plants grown at a high elevated pCO₂ (> 90 Pa), which show evidence of an excess investment in Rubisco, the failure to maintain the initial stimulation of A is almost entirely attributable to the decrease in V_c,max and investment in Rubisco is coupled to requirements.     

Nitrogen supply as a factor influencing photoinhibition and photosynthetic acclimation after transfer of shade-grown Solanum dulcamara to bright light

We have compared the ability of shadegrown clones of Solamum dulcamara L. from shade and sun habitats to acclimate to bright light, as a function of nitrogen nutrition before and after transfer to bright light. Leaves of S. dulcamara grown in the shade with 0.6 mM NO ₃ ^- have similar photosynthetic properties as leaves of plants grown with 12.0 mM NO ₃ ^- . When transferred to bright light for 1–2 d the leaves of these plants show substantial photoinhibition which is characterized by about 50% decrease in apparent quantum yield and a reduction in the rate of photosynthesis in air at light saturation. Photoinhibition of leaf photosynthesis is associated with reduction in the variable component of low-temperature fluorescence emission, and with loss of in-vitro electron transport, especially of photosystem II-dependent processes.We find no evidence for ecotypic differentiation in the potential for photosynthetic acclimation among shade and sun clones of S. dulcamara, or of differentiation with respect to nitrogen requirements for acclimation. Recovery from photoinhibition and subsequent acclimation of photosynthesis to bright light only occurs in leaves of plants provided with 12.0 mM NO ₃ ^- . In these, apparent quantum yield is fully restored after 14 d, and photosynthetic acclimation is shown by an increase in light-saturated photosynthesis in air, of light-and CO₂-saturated photosynthesis, and of the initial slope of the CO₂-response curve. The latter changes are highly correlated with changes in ribulose-bisphosphate-carboxylase activity in vitro. Plants supplied with 0.6 mM NO ₃ ^- show incomplete recovery of apparent quantum yield after 14 d, but CO₂-dependent leaf photosynthetic parameters return to control levels.Symbols and abbreviations F_o initial level of fluorescence at 77 K - F_m maximum level of fluorescence at 77 K - F_v variable components of fluorescence at 77 K (F_v=F_m-F_o) - PSI, PSII photosystem I and II, respectively - RuBP ribulose-1,5-bisphosphate - RuBPCase ribulose-1,5-bisphosphate carboxylase-oxygenase (EC 4.1.1.39)     

Protein kinases and phosphatases involved in the acclimation of the photosynthetic apparatus to a changing light environment

Photosynthetic organisms are subjected to frequent changes in light quality and quantity and need to respond accordingly. These acclimatory processes are mediated to a large extent through thylakoid protein phosphorylation. Recently, two major thylakoid protein kinases have been identified and characterized. The Stt7/STN7 kinase is mainly involved in the phosphorylation of the LHCII antenna proteins and is required for state transitions. It is firmly associated with the cytochrome b₆f complex, and its activity is regulated by the redox state of the plastoquinone pool. The other kinase, Stl1/STN8, is responsible for the phosphorylation of the PSII core proteins. Using a reverse genetics approach, we have recently identified the chloroplast PPH1/TAP38 and PBPC protein phosphatases, which counteract the activity of STN7 and STN8 kinases, respectively. They belong to the PP2C-type phosphatase family and are conserved in land plants and algae. The picture that emerges from these studies is that of a complex regulatory network of chloroplast protein kinases and phosphatases that is involved in light acclimation, in maintenance of the plastoquinone redox poise under fluctuating light and in the adjustment to metabolic needs.     

Effects of weather during leaf development on photosynthetic characteristics of soybean leaves

Net photosynthetic rates and mesophyll conductances at 25 °C at light saturation and air levels of carbon dioxide and oxygen were measured on recently fully expanded leaflets of second trifoliolate leaves of soybeans (Glycine max cv. Kent). Plants were grown outdoors in pots at Beltsville, Maryland with 14 planting times from May through August, 1983. Air temperature and humidity, and photosynthetically active radiation (PAR) were measured for the expansion periods of the second trifoliolate leaves. Rates of net photosynthesis ranged from 24 to 33 mol m^–2 s^–1, and mesophyll conductances from 0.24 to 0.35 cm s^–1 for the different planting dates. Mean 24-h air temperatures ranged from 20.6 to 29.0 °C, and mean daily PAR ranged from 29.4 to 58.4 mol m^–2 d^–1 for the leaf expansion periods. There was a positive relationship between photosynthetic characteristics and PAR during leaf expansion, and a negative relationship between photosynthetic characteristics and leaf expansion rates, with 96% of the variation in photosynthetic characteristics accounted for by these two variables. Leaf expansion rates were highly correlated with air temperature.     

斑马鱼热耐受性对温度驯化的响应及其性别差异

为了探究斑马鱼(Danio rerio)热耐受性对温度驯化的响应及其性别差异,将性成熟斑马鱼分别于适温(28℃)、低温(20℃)和高温(34℃)下驯化14 d,之后测定不同温度驯化下雌鱼和雄鱼的临界高温(critical thermal maxima,CTmax)、致死高温(lethal thermal maxima,LTmax)、临界低温(critical thermal minima,CTmin)、致死低温(lethal thermal minima,LTmin)等热耐受性参数.结果表明:驯化温度对雄鱼和雌鱼的所有热忍耐参数(CTmax、LTmax、CTmin和LTmin)均影响显著(P<0.05),并且驯化温度和性别对热耐受性参数的影响具有交互作用(P<0.05).适温(28℃)驯化下,雌鱼与雄鱼各个热忍耐参数相比无显著差异(P> 0.05);低温(20℃)驯化下雌鱼的耐高温能力强于雄鱼,而高温(34℃)驯化下雌鱼的耐低温能力弱于雄鱼.结果提示:繁殖适温下雌雄斑马鱼的热耐受性趋于一致,而非繁殖适温下二者的热耐受性出现分化.     

Influence of photoperiod on low temperature acclimation for cold-hardiness in Drosophila auraria

ABSTRACT. Imagines of Drosophila auraria Peng, a reproductive diapause species, developed cold-hardiness at low temperatures to a greater extent when exposed to a diapause-inducing photoperiod (LD10:14 h) than when exposed to a diapause-preventing photoperiod (LD 16:8h). Imagines kept at 18°C, which was the temperature at which they were reared to eclosion, did not survive a test exposure to -5°C for 8 days regardless of age or photoperiod. When transferred to 10 or 5°C, either from eclosion or from 8 days after eclosion, the survival rate, on testing, rose with time since transfer and rose faster and higher with a photoperiod of LD 10:14h than with LD16:8h. Flies transferred to 15°C only showed improved ability to survive the test if they were kept in LD 10:14h. When cultured at 18°C to the age of 8 days after eclosion, diapause was terminated in about 30% of females even at LD 10:14h. In these post-diapause females the ability to develop cold-hardiness at lower temperatures was somewhat less than in the diapausing females, but apparently greater than in the non-diapause females. These results suggest that the physiological mechanism which promotes cold-hardiness under a diapause-inducing photoperiod is not directly linked to the process causing reproductive diapause.
In Sapporo, flies from a natural population became tolerant to cold in October when they entered diapause and daily mean temperature fell below 15°C and the light/dark cycle fell below LD 12:12h.     

Protein, leucine aminopeptidase, esterase, acid phosphatase and photosynthetic responses of oleander (Nerium oleander L.) during cold acclimation and freezing treatments

Six-month-old oleander (Nerium oleander L.) pot plants, derived from vegetative propagation by cuttings, were tested for their ability to cold hardening. Damage of the non-acclimated (NA) plants was visible when treated by low freezing temperatures (below -2 degrees C). The responses of total proteins, leucine aminopeptidase (LAP), esterase (EST) and acid phosphatase (ACP) isoforms of NA and cold-acclimated (CA; 4 degrees C for 14 days) plants were compared using polyacrylamide gel electrophoresis. These molecular markers were also compared in NA and CA plants which received for 2h temperatures of 0, -2, -4, -6 and -8 degrees C. A new 38-kDa polypeptide appeared from day 7 to 14 during the acclimation treatment in the bark extracts and on day 14 in the leaf extracts. The above-mentioned polypeptide band (38 kDa) strongly appeared in all freezing treatments (0, -2, -4, -6 and -8 degrees C) in both bark and leaf extracts of the CA plants. Alterations in the number and the intensity of LAP and EST isoforms as well as in the intensity of ACP isoforms were observed in both bark and leaf of the CA oleander plants. A newly expressed EST isoform is proposed as biochemical marker for the cold acclimation treatment. CO2 assimilation rates (A) as well as transpiration rates (E) in NA plants were positive in 0 degrees C and negative in all temperatures below zero in the freezing treatments. In contrast, CO2 assimilation rates (A) and transpiration rates (E) were positive in CA plants in all temperatures of freezing treatment. A significant decrease (P<0.05) in chlorophyll (Chl) a, Chl a+b concentration and Chl a/b ratio were noticed in oleander plants during the acclimation treatment (from day 0 to 14), while Chl b concentration was unchanged at the respective time. On the other hand, no significant (P<0.05) differences were observed in the freezing treatments.     

Importance of leaf versus whole plant CO2 environment for photosynthetic acclimation

The reduction of photosynthetic capacity in many plants grown at elevated CO₂ is thought to result from a feedback effect of leaf carbohydrates on gene expression. Carbohydrate feedback at elevated CO₂ could result from limitations on carbohydrate utilization at many different points, for example export of triose phosphates from the chloroplast, sucrose synthesis and phloem loading, transport in the phloem, unloading of the phloem at the sinks, or utilization for growth of sinks. To determine the relative importance of leaf versus whole plant level limitations on carbohydrate utilization at elevated CO₂, and the possible effects on the regulation of photosynthetic capacity, we constructed a treatment system in which we could expose single, attached, soybean leaflets to CO₂ concentrations different from those experienced by the rest of the plant. The single leaflet treatments had dramatic effects on the carbohydrate contents of the treated leaflets. However, photosynthetic capacity and rubisco content were unaffected by the individual leaflet treatment and instead were related to the whole plant CO₂ environment, despite the fact that the CO₂ environment around the rest of the plant had no significant affect on the total non-structural carbohydrate (TNC) contents of the treated leaflets. These results necessitate a re-evaluation of the response mechanisms to CO₂ as well as some of the methods used to test these responses. We propose mechanisms by which sink strength could influence leaf physiology independently of changes in carbohydrate accumulation.     

Intraspecific variation in temperature dependence of gas exchange characteristics among Plantago asiatica ecotypes from different temperature regimes

There are large inter- and intraspecific differences in the temperature dependence of photosynthesis, but the physiological cause of the variation is poorly understood. Here, the temperature dependence of photosynthesis was examined in three ecotypes of Plantago asiatica transplanted from different latitudes, where the mean annual temperature varies between 7.5 and 16.8 degrees C. Plants were raised at 15 or 30 degrees C, and the CO(2) response of photosynthetic rates was determined at various temperatures. When plants were grown at 30 degrees C, no difference was found in the temperature dependence of photosynthesis among ecotypes. When plants were grown at 15 degrees C, ecotypes from a higher latitude maintained a relatively higher photosynthetic rate at low measurement temperatures. This difference was caused by a difference in the balance between the capacities of two processes, ribulose-1,5-bisphosphate regeneration (J(max)) and carboxylation (V(cmax)), which altered the limiting step of photosynthesis at low temperatures. The organization of photosynthetic proteins also varied among ecotypes. The ecotype from the highest latitude increased the J(max) : V(cmax) ratio with decreasing growth temperature, while that from the lowest latitude did not. It is concluded that nitrogen partitioning in the photosynthetic apparatus and its response to growth temperature were different among ecotypes, which caused an intraspecific variation in temperature dependence of photosynthesis.     

Contrasting patterns of photosynthetic acclimation to the light environment are dependent on the differential expression of the responses to altered irradiance and spectral quality

Chl, chlorophyll
Chl a/b, ratio of chlorophyll a to chlorophyll b
Cyt f, cytochrome f
FR, far-red light
LFR, low irradiance, far-red enriched growth light
LHCII, light harvesting complex associated with PSII
LW, low irradiance, white growth light
MW, moderate irradiance, white growth light
PAR, photosynthetically active radiation
P_max, light and CO₂ saturated photosynthetic rate
PSI, photosystem I
PSII, photosystem II

Four plant species (Chamerion angustifolium, Digitalis purpurea, Brachypodium sylvaticum and Plantago lanceolata) which have previously been shown to demonstrate contrasting photosynthetic acclimatory responses to the light environment ( 33 , Plant, Cell and Environment 20, pp. 438–448) were analysed at a biochemical level. Plants were grown under low irradiance with a shade-type spectrum (LFR: 50μmol quanta m^–2 s^–1), moderately high white light (MW: 300μmol quanta m^–2 s^–1) and low irradiance white light (LW: 50μmol quanta m^–2 s^–1). The effects of light quality upon chlorophyll content and photosynthetic capacity were found to be species-dependent. A far-red dependent reduction in chlorophyll was found in three species, and an irradiance-dependent reduction was found in B. sylvaticum, which showed the greatest alteration in the xanthophyll cycle pool size of all species tested under these conditions. Chlorophyll a/b ratios were sensitive to both light quality and quantity in C. angustifolium and D. purpurea, being highest in MW, lowest in LFR, and intermediate in LW, whilst the other species showed no response. Ratios of photosystem II to photosystem I (PSII and PSI) demonstrated a strong irradiance-associated increase in all species except B. sylvaticum, whereas an increase in PSII/PSI in LFR compared to LW conditions was present in all species. A change in chlorophyll a/b was not always associated with a change in PSII/PSI, suggesting that the level of LHCII associated with each PSII varied in some species. Cytochrome f content showed an irradiance-dependent effect only, indicating a relationship with the capacity of electron transport. It is concluded that differing strategies of acclimation to the light environment demonstrated by these species results from differing strengths of expression of a series of independently regulated changes in the levels of photosynthetic components.     

Multiple aminoacyl-tRNA synthetases (translases) in temperature acclimation of eurythermal fish

The temperature dependency of activity of the entire set of aminoacyl-tRNA synthetases (protein synthetic translases) has been studied in the laboratory rat and in toadfish (Opsanus tau) acclimated to 20 δC or to 10 δC. The complex temperature responses of these enzyme systems reveal the presence of multiple forms for the translases of most amino acids and show adaptive behavior of these systems with respect to body temperature of the animal. The phenylalanine translase system has been studied in detail, and adaptation of this system at low temperatures correlates with adaptation in the elongation factor system. All known protein synthetic components appear to be coordinated in adaptive responses with the exception of ribosomes. Our data indicate no rôle for ribosomes in adaptation of the protein synthetic system and apparently no rôle for ribosomes in protein synthesis at all in rat and fish. This finding may solve some long-standing paradoxes in the protein synthesis field concerning the mechanism by which ribosomes participate in protein synthesis.     

Surface temperatures of growing pigs in relation to the duration of acclimation to air temperature or draught

The aim of this work was to study to what extent surface temperatures of growing pigs are altered during acclimation to a change of the air temperature and to exposure to draught.

4 groups of 10 pigs (Large White × Dutch Landrace) of approximately 10 weeks old were used. They were housed in 2 calorimeters with 2 pens each. In the reference chamber air temperature was kept constant at 25°C, in the other chamber air temperature could be lowered to 15°C, and a draught was also applied. Surface temperatures of the pigs were measured by means of Probey® Thermal Video System, with an accuracy of ±0.3°C.

Surface temperatures of growing pigs were obviously related to air temperature, draught and the duration of food withdrawal. Acclimation to air temperature or draught as measured by surface temperatures was not observed between days, but within and between night periods.

Also indications of huddling, vasocontriction and even cold-induced vasodilatation within the neck, chest and abdomen region of the pigs' body surface were observed.     

Acclimation of the respiration/photosynthesis ratio to temperature: insights from a model

Based on short-term experiments, many plant growth models – including those used in global change research – assume that an increase in temperature stimulates plant respiration (R) more than photosynthesis (P), leading to an increase in the R/P ratio. Longer-term experiments, however, have demonstrated that R/P is relatively insensitive to growth temperature. We show that both types of temperature response may be reconciled within a simple substrate-based model of plant acclimation to temperature, in which respiration is effectively limited by the supply of carbohydrates fixed through photosynthesis. The short-term, positive temperature response of R/P reflects the transient dynamics of the nonstructural carbohydrate and protein pools; the insensitivity of R/P to temperature on longer time-scales reflects the steady-state behaviour of these pools. Thus the substrate approach may provide a basis for predicting plant respiration responses to temperature that is more robust than the current modelling paradigm based on the extrapolation of results from short-term experiments. The present model predicts that the acclimated R/P depends mainly on the internal allocation of carbohydrates to protein synthesis, a better understanding of which is therefore required to underpin the wider use of a constant R/P as an alternative modelling paradigm in global change research.