共查询到20条相似文献,搜索用时 15 毫秒
1.
D. E. Pataki T. E. Huxman D. N. Jordan S. F. Zitzer J. S. Coleman S. D. Smith R. S. Nowak J. R. Seemann 《Global Change Biology》2000,6(8):889-897
Plant responses to elevated atmospheric CO2 have been characterized generally by stomatal closure and enhanced growth rates. These responses are being increasingly incorporated into global climate models that quantify interactions between the biosphere and atmosphere, altering climate predictions from simpler physically based models. However, current information on CO2 responses has been gathered primarily from studies of crop and temperate forest species. In order to apply responses of vegetation to global predictions, CO2 responses in other commonly occurring biomes must be studied. A Free Air CO2 Enrichment (FACE) study is currently underway to examine plant responses to high CO2 in a natural, undisturbed Mojave Desert ecosystem in Nevada, USA. Here we present findings from this study, and its companion glasshouse experiment, demonstrating that field‐grown Ephedra nevadensis and glasshouse‐grown Larrea tridentata responded to high CO2 with reductions in the ratio of transpirational surface area to sapwood area (LSR) of 33% and 60%, respectively. Thus, leaf‐specific hydraulic conductivity increased and stomatal conductance remained constant or was increased under elevated CO2. Field‐grown Larrea did not show a reduced LSR under high CO2, and stomatal conductance was reduced in the high CO2 treatment, although the effect was apparent only under conditions of unusually high soil moisture. Both findings suggest that the common paradigm of 20–50% reductions in stomatal conductance under high CO2 may not be applicable to arid ecosystems under most conditions. 相似文献
2.
Although desert ecosystems are predicted to be the most responsive to elevated CO2, low nutrient availability may limit increases in productivity and cause plants in deserts to allocate more resources to root biomass or activity for increased nutrient acquisition. We measured root respiration of two Mojave Desert shrubs, Ambrosia dumosa and Larrea tridentata, grown under ambient (~375 ppm) and elevated (~517 ppm) CO2 concentrations at the Nevada Desert FACE Facility (NDFF) over five growing seasons. In addition, we grew L. tridentata seedlings in a greenhouse with similar CO2 treatments to determine responses of primary and lateral roots to an increase in CO2. In both field and greenhouse studies, root respiration was not significantly affected by elevated CO2. However, respiration of A. dumosa roots <1 month old was significantly greater than respiration of A. dumosa roots between 1 and 4 months old. For both shrub species, respiration rates of very fine (<1.0 mm diameter) roots were significantly greater than those of fine (1–2 mm diameter) roots, and root respiration decreased as soil water decreased. Because specific root length was not significantly affected by CO2 and because field minirhizotron measurements of root production were not significantly different, we infer that root growth at the NDFF has not increased with elevated CO2. Furthermore, other studies at the NDFF have shown increased nutrient availability under elevated CO2, which reduces the need for roots to increase scavenging for nutrients. Thus, we conclude that A. dumosa and L. tridentata root systems have not increased in size or activity, and increased shoot production observed under elevated CO2 for these species does not appear to be constrained by the plant's root growth or activity. 相似文献
3.
Beth A. Newingham Cheryl H. Vanier Therese N. Charlet Kiona Ogle Stanley D. Smith Robert S. Nowak 《Global Change Biology》2013,19(7):2168-2181
Elevated atmospheric CO2 concentrations ([CO2]) generally increase primary production of terrestrial ecosystems. Production responses to elevated [CO2] may be particularly large in deserts, but information on their long‐term response is unknown. We evaluated the cumulative effects of elevated [CO2] on primary production at the Nevada Desert FACE (free‐air carbon dioxide enrichment) Facility. Aboveground and belowground perennial plant biomass was harvested in an intact Mojave Desert ecosystem at the end of a 10‐year elevated [CO2] experiment. We measured community standing biomass, biomass allocation, canopy cover, leaf area index (LAI), carbon and nitrogen content, and isotopic composition of plant tissues for five to eight dominant species. We provide the first long‐term results of elevated [CO2] on biomass components of a desert ecosystem and offer information on understudied Mojave Desert species. In contrast to initial expectations, 10 years of elevated [CO2] had no significant effect on standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground components. However, elevated [CO2] increased short‐term responses, including leaf water‐use efficiency (WUE) as measured by carbon isotope discrimination and increased plot‐level LAI. Standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground pools significantly differed among dominant species, but responses to elevated [CO2] did not vary among species, photosynthetic pathway (C3 vs. C4), or growth form (drought‐deciduous shrub vs. evergreen shrub vs. grass). Thus, even though previous and current results occasionally show increased leaf‐level photosynthetic rates, WUE, LAI, and plant growth under elevated [CO2] during the 10‐year experiment, most responses were in wet years and did not lead to sustained increases in community biomass. We presume that the lack of sustained biomass responses to elevated [CO2] is explained by inter‐annual differences in water availability. Therefore, the high frequency of low precipitation years may constrain cumulative biomass responses to elevated [CO2] in desert environments. 相似文献
4.
Elevated atmospheric CO2 has been shown to rapidly alter plant physiology and ecosystem productivity, but contemporary evolutionary responses to increased CO2 have yet to be demonstrated in the field. At a Mojave Desert FACE (free‐air CO2 enrichment) facility, we tested whether an annual grass weed (Bromus madritensis ssp. rubens) has evolved in response to elevated atmospheric CO2. Within 7 years, field populations exposed to elevated CO2 evolved lower rates of leaf stomatal conductance; a physiological adaptation known to conserve water in other desert or water‐limited ecosystems. Evolution of lower conductance was accompanied by reduced plasticity in upregulating conductance when CO2 was more limiting; this reduction in conductance plasticity suggests that genetic assimilation may be ongoing. Reproductive fitness costs associated with this reduction in phenotypic plasticity were demonstrated under ambient levels of CO2. Our findings suggest that contemporary evolution may facilitate this invasive species' spread in this desert ecosystem. 相似文献
5.
Effects of elevated [CO2] and/or ozone on limitations to CO2 assimilation in soybean (Glycine max) 总被引:3,自引:0,他引:3
Soybean (Glycine max) was grown in open-top field
chambers at ambient (360 mol
mol-1) or doubled [CO2] either in charcoal-filtered
air (20 nmol mol-1 [O3]) or in non-filtered air
supplemented to 1,5 x ambient [O3] (70 nmol mol-1)
to determine the major limitations to assimilation under conditions of
elevated [CO2] and/or [O3]. Through plant ontogeny, assimilation versus
intercellular CO2 concentration (A/Ci) responses were
measured to assess the limitations to assimilation imposed by the capacity
for Rubisco carboxylation, RuBP regeneration, and stomatal diffusion.In the
vegetative stages, no significant treatment effects of elevated [CO2]
and/or [O3] were observed on Rubisco carboxylation efficiency
(CE), light and CO2-saturated assimilation capacity
(Amax), and chlorophyll content
(Chl). However, for plants grown in elevated [CO2],
the assimilation rate at growth [CO2] (A) was 60%
higher than at ambient [CO2] up to the seed maturation stage, and the
potential rate of assimilation by Rubisco capacity
(Ap) was increased. Also in elevated [CO2]:
A was 51% of Ap; the relative
stomatal limitation (%Stomata) was 5%; and the
relative RuBP regeneration limitation (%RuBP) was 44%.
In ambient [CO2], O3 gradually decreased A per unit
leaf area, but had little effect on Ap and the
relative limitations to assimilation where A remained
51% of Ap, %Stomata was 27%, and
%RuBP was 22%.During reproduction,
CE declined for plants grown in elevated [CO2] and/or
[O3]; Ap was unaffected by elevated [CO2], but was
reduced by [O3] at ambient [CO2]; A increased to 72%
of Ap in elevated [CO2] and/or [O3]-fumigated air; the
%Stomata increased; and the %RuBP
decreased, to become non significant in elevated [CO2] from the beginning
of seed growth on, and in O3-fumigated air at ambient [CO2] at the seed
maturation stage. The decrease in %RuBP occurred
concomitantly with an increase in Amax and
Chl. Significant [CO2] x [O3] interactions support the
lack of an O3 effect on assimilation and its limitations at elevated [CO2]
during seed maturation. These data suggest that elevated [CO2] alleviated
some of the effects of O3 on photosynthesis.Keywords:
CO2 by O3 interactions, elevated [CO2], O3 fumigation, Rubisco
carboxylation efficiency, RuBP regeneration.
相似文献
6.
Changes in plant inputs under changing atmospheric CO2 can be expected to alter the size and/or functional characteristics of soil microbial communities which can determine whether soils are a C sink or source. Stable isotope probing was used to trace autotrophically fixed 13C into phospholipid fatty acid (PLFA) biomarkers in Mojave Desert soils planted with the desert shrub, Larrea tridentata. Seedlings were pulse‐labeled with 13CO2 under ambient and elevated CO2 in controlled environmental growth chambers. The label was chased into the soil by extracting soil PLFAs after labeling at Days 0, 2, 10, 24, and 49. Eighteen of 29 PLFAs identified showed 13C enrichment relative to nonlabeled control soils. Patterns of PLFA enrichment varied temporally and were similar for various PLFAs found within a microbial functional group. Enrichment of PLFA 13C generally occurred within the first 2 days in general and fungal biomarkers, followed by increasingly greater enrichment in bacterial biomarkers as the study progressed (Gram‐negative, Gram‐positive, actinobacteria). While treatment CO2 level did not affect total PLFA‐C concentrations, microbial functional group abundances and distribution responded to treatment CO2 level and these shifts persisted throughout the study. Specifically, ratios of bacterial‐to‐total PLFA‐C decreased and fungal‐to‐bacterial PLFA‐C increased under elevated CO2 compared with ambient conditions. Differences in the timing of 13C incorporation into lipid biomarkers coupled with changes in microbial functional groups indicate that microbial community characteristics in Mojave Desert soils have shifted in response to long‐term exposure to increased atmospheric CO2. 相似文献
7.
Nitrogen assimilation and transpiration: key processes conditioning responsiveness of wheat to elevated [CO2] and temperature
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Iván Jauregui Ricardo Aroca María Garnica Ángel M. Zamarreño José M. García‐Mina Maria D. Serret Martin Parry Juan J. Irigoyen Iker Aranjuelo 《Physiologia plantarum》2015,155(3):338-354
Although climate scenarios have predicted an increase in [CO2] and temperature conditions, to date few experiments have focused on the interaction of [CO2] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO2. The main goal of this study was to analyze the effect of interacting [CO2] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO2] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO2] (400 vs 700 µmol mol?1) and temperature (ambient vs ambient + 4°C) in CO2 gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO2] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO2] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient transport in leaves of plants exposed to elevated [CO2] and temperature, led to mineral depletion and therefore contributed to the inhibition of photosynthetic activity. 相似文献
8.
Annual and short-lived perennial plant performance during wet years is important for long-term persistence in the Mojave Desert. Additionally, the effects of elevated CO2 on desert plants may be relatively greater during years of high resource availability compared to dry years. Therefore, during an El Niño year at the Nevada Desert FACE Facility (a whole-ecosystem CO2 manipulation), we characterized photosynthetic investment (by assimilation rate-internal CO2 concentration relationships) and evaluated the seasonal pattern of net photosynthesis (Anet) and stomatal conductance (gs) for an invasive annual grass, Bromus madritensis ssp. rubens and a native herbaceous perennial, Eriogonum inflatum. Prior to and following flowering, Bromus showed consistent increases in both the maximum rate of carboxylation by Rubisco (VCmax) and the light-saturated rate of electron flow (Jmax) at elevated CO2. This resulted in greater Anet at elevated CO2 throughout most of the life cycle and a decrease in the seasonal decline of maximum midday Anet upon flowering as compared to ambient CO2. Eriogonum showed significant photosynthetic down-regulation to elevated CO2 late in the season, but the overall pattern of maximum midday Anet was not altered with respect to phenology. For Eriogonum, this resulted in similar levels of Anet on a leaf area basis as the season progressed between CO2 treatments, but greater photosynthetic activity over a typical diurnal period. While gs did not consistently vary with CO2 in Bromus, it did decrease in Eriogonum at elevated CO2 throughout much of the season. Since the biomass of both plants increased significantly at elevated CO2, these patterns of gas exchange highlight the differential mechanisms for increased plant growth. The species-specific interaction between CO2 and phenology in different growth forms suggests that important plant strategies may be altered by elevated CO2 in natural settings. These results indicate the importance of evaluating the effects of elevated CO2 at all life cycle stages to better understand the effects of elevated CO2 on whole-plant performance in natural ecosystems. 相似文献
9.
10.
Photosynthetic responses of Mojave Desert shrubs to free air CO2 enrichment are greatest during wet years 总被引:2,自引:0,他引:2
Elke Naumburg† David C. Housman Travis E. Huxman‡ Therese N. Charlet Michael E. Loik§ Stanley D. Smith 《Global Change Biology》2003,9(2):276-285
It has been suggested that desert vegetation will show the strongest response to rising atmospheric carbon dioxide due to strong water limitations in these systems that may be ameliorated by both photosynthetic enhancements and reductions in stomatal conductance. Here, we report the long‐term effect of 55 Pa atmospheric CO2 on photosynthesis and stomatal conductance for three Mojave Desert shrubs of differing leaf phenology (Ambrosia dumosa—drought‐deciduous, Krameria erecta—winter‐deciduous, Larrea tridentata—evergreen). The shrubs were growing in an undisturbed ecosystem fumigated using FACE technology and were measured over a four‐year period that included both above and below‐average precipitation. Daily integrated photosynthesis (Aday) was significantly enhanced by elevated CO2 for all three species, although Krameria erecta showed the greatest enhancements (63% vs. 32% for the other species) enhancements were constant throughout the entire measurement period. Only one species, Larrea tridentata, decreased stomatal conductance by 25–50% in response to elevated CO2, and then only at the onset of the summer dry season and following late summer convective precipitation. Similarly, reductions in the maximum carboxylation rate of Rubisco were limited to Larrea during spring. These results suggest that the elevated CO2 response of desert vegetation is a function of complex interactions between species functional types and prevailing environmental conditions. Elevated CO2 did not extend the active growing season into the summer dry season because of overall negligible stomatal conductance responses that did not result in significant water conservation. Overall, we expect the greatest response of desert vegetation during years with above‐average precipitation when the active growing season is not limited to ~ 2 months and, consequently, the effects of increased photosynthesis can accumulate over a biologically significant time period. 相似文献
11.
Arid ecosystems, which occupy about 35% of the Earth's terrestrial surface area, are believed to be among the most responsive to elevated [CO2]. Net ecosystem CO2 exchange (NEE) was measured in the eighth year of CO2 enrichment at the Nevada Desert Free‐Air CO2 Enrichment (FACE) Facility between the months of December 2003–December 2004. On most dates mean daily NEE (24 h) (μmol CO2 m?2 s?1) of ecosystems exposed to elevated atmospheric CO2 were similar to those maintained at current ambient CO2 levels. However, on sampling dates following rains, mean daily NEEs of ecosystems exposed to elevated [CO2] averaged 23 to 56% lower than mean daily NEEs of ecosystems maintained at ambient [CO2]. Mean daily NEE varied seasonally across both CO2 treatments, increasing from about 0.1 μmol CO2 m?2 s?1 in December to a maximum of 0.5–0.6 μmol CO2 m?2 s?1 in early spring. Maximum NEE in ecosystems exposed to elevated CO2 occurred 1 month earlier than it did in ecosystems exposed to ambient CO2, with declines in both treatments to lowest seasonal levels by early October (0.09±0.03 μmol CO2 m?2 s?1), but then increasing to near peak levels in late October (0.36±0.08 μmol CO2 m?2 s?1), November (0.28±0.03 μmol CO2 m?2 s?1), and December (0.54±0.06 μmol CO2 m?2 s?1). Seasonal patterns of mean daily NEE primarily resulted from larger seasonal fluctuations in rates of daytime net ecosystem CO2 uptake which were closely tied to plant community phenology and precipitation. Photosynthesis in the autotrophic crust community (lichens, mosses, and free‐living cyanobacteria) following rains were probably responsible for the high NEEs observed in January, February, and late October 2004 when vascular plant photosynthesis was low. Both CO2 treatments were net CO2 sinks in 2004, but exposure to elevated CO2 reduced CO2 sink strength by 30% (positive net ecosystem productivity=127±17 g C m?2 yr?1 ambient CO2 and 90±11 g C m?2 yr?1 elevated CO2, P=0.011). This level of net C uptake rivals or exceeds levels observed in some forested and grassland ecosystems. Thus, the decrease in C sequestration seen in our study under elevated CO2– along with the extensive coverage of arid and semi‐arid ecosystems globally – points to a significant drop in global C sequestration potential in the next several decades because of responses of heretofore overlooked dryland ecosystems. 相似文献
12.
Georg Frenck Leon van der Linden Teis Nørgaard Mikkelsen Hans Brix Rikke Bagger Jørgensen 《Ecology and evolution》2013,3(5):1163-1172
Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi‐generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO2] and temperature conditions, a full‐factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO2] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO2] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co‐occur. 相似文献
13.
Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of plants with the C4 pathway. An increase in the CO2 concentration can therefore be expected to change the competitive interactions between C3 and C4 species. The effect of long term exposure to elevated CO2 (ambient CO2 concentration +340 µmol CO2 mol-1) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of the C3 sedgeScirpus olneyi growing in a pure stand, while the biomass of the C4 grassSpartina patens in a monospecific community was not affected. In the mixed C3/C4 community the C3 sedge showed a very large relative increase in biomass in elevated CO2 while the biomass of the C4 species declined.The C4 grassSpartina patens dominated the higher areas of the salt marsh, while the C3 sedgeScirpus olneyi was most abundant at the lower elevations, and the mixed community occupied intermediate elevations.Scirpus growth may have been restricted by drought and salt stress at the higher elevations, whileSpartina growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may affect the species distribution in the salt marsh if it allowsScirpus to grow at higher elevations where it in turn may affect the growth ofSpartina. 相似文献
14.
It is unclear how changing atmospheric composition will influence the plant–soil interactions that determine soil organic
matter (SOM) levels in fertile agricultural soils. Positive effects of CO2 fertilization on plant productivity and residue returns should increase SOM stocks unless mineralization or biomass removal
rates increase in proportion to offset gains. Our objectives were to quantify changes in SOM stocks and labile fractions in
prime farmland supporting a conventionally managed corn–soybean system and the seasonal dynamics of labile C and N in soybean
in plots exposed to elevated [CO2] (550 ppm) under free-air concentration enrichment (FACE) conditions. Changes in SOM stocks including reduced C/N ratios
and labile N stocks suggest that SOM declined slightly and became more decomposed in all plots after 3 years. Plant available
N (>273 mg N kg−1) and other nutrients (Bray P, 22–50 ppm; extractable K, 157–237 ppm; Ca, 2,378–2,730 ppm; Mg, 245–317 ppm) were in the high
to medium range. Exposure to elevated [CO2] failed to increase particulate organic matter C (POM-C) and increased POM-N concentrations slightly in the surface depth
despite known increases (≈30%) in root biomass. This, and elevated CO2 efflux rates indicate accelerated decay rates in fumigated plots (2001: elevated [CO2]: 10.5 ± 1.2 μmol CO2 m−2 s−1 vs. ambient: 8.9 ± 1.0 μmol CO2 m−2 s−1). There were no treatment-based differences in the within-season dynamics of SOM. Soil POM-C and POM-N contents were slightly
greater in the surface depth of elevated than ambient plots. Most studies attribute limited ability of fumigated soils to
accumulate SOM to N limitation and/or limited plant response to CO2 fertilization. In this study, SOM turnover appears to be accelerated under elevated [CO2] even though soil moisture and nutrients are non-limiting and plant productivity is consistently increased. Accelerated SOM
turnover rates may have long-term implications for soil’s productive potential and calls for deeper investigation into C and
N dynamics in highly-productive row crop systems. 相似文献
15.
Pseudovivipary is an asexual reproductive strategy exhibited by some arctic/alpine grasses in which leafy plantlets are produced in place of seeds, with genetic conservation an advantage for stress tolerators in these nutrient-poor habitats. Photosynthetic metabolism and the development of this reproductive system were investigated under varying nutrient availability and predicted future CO(2) partial pressure (pCO(2)). Poa alpina var. vivipara L., grown at present ambient pCO(2) or ambient plus 340 micro mol mol(-1) CO(2) (elevated pCO(2)), was supplied with either 0.05 mol m(-3) phosphorus and 0.2 mol m(-3) nitrogen, or 0.2 mol m(-3) phosphorus and 1.0 mol m(-3) nitrogen. Gas exchange measurements and determination of total non-structural carbohydrate (TNC), nitrogen and phosphorus contents revealed that parent plant leaf blade tissues experienced acclimatory loss of photosynthetic capacity after long-term growth at elevated pCO(2) (particularly so when nutrient availability was low); there were associated reductions in photosynthetic nitrogen and phosphorus use efficiencies (PNUE and PPUE). In addition, decreased PNUE and PPUE were exhibited by plantlets grown at elevated pCO(2) with low nutrient availability. Decreased reproductive dry matter in this treatment also resulted from a lack of reproductive initiation in daughter tillers, and altered phenology. Pseudoviviparous P. alpina is likely to be at a disadvantage in both vegetative and reproductive phases at predicted future elevated atmospheric CO(2) concentrations, particularly where nutrients are scarce and when in competition with species experiencing less acclimatory loss of photosynthetic capacity. 相似文献
16.
Understanding how photosynthetic capacity acclimatises when plants are grown in an atmosphere of rising CO2 concentrations will be vital to the development of mechanistic models of the response of plant productivity to global environmental change. A limitation to the study of acclimatisation is the small amount of material that may be destructively harvested from long-term studies of the effects of elevation of CO2 concentration. Technological developments in the measurement of gas exchange, fluorescence and absorption spectroscopy, coupled with theoretical developments in the interpretation of measured values now allow detailed analyses of limitations to photosynthesisin vivo. The use of leaf chambers with Ulbricht integrating spheres allows separation of change in the maximum efficiency of energy transduction in the assimilation of CO2 from changes in tissue absorptance. Analysis of the response of CO2 assimilation to intercellular CO2 concentration allows quantitative determination of the limitation imposed by stomata, carboxylation efficiency, and the rate of regeneration of ribulose 1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method for detecting photoinhibition in heterogeneously illuminated leaves within canopies in the field. Modulated fluorescence and absorption spectroscopy allow parallel measurements of the efficiency of light utilisation in electron transport through photosystems I and IIin situ.Abbreviations A
net rate of CO2 uptke per unit leaf area (µmol m–2 s–1)
- Asat
light-saturated A
- A820
change in absorptance of PSI on removal of illumination (OD)
- c
CO2 concentration in air (µmol mol–1)
- ca
c in the bulk air; ci, c in the intercellular spaces
- ce
carboxylation efficiency (mol m–2 s–1)
- E
transpiration per unit leaf area (mol m–2 s–1)
- F
fluorescence emission of PSII (relative units)
- Fm
maximal level of F
- Fo
minimal level of F upon illumination when PSII is maximally oxidised
- Fs
the steady-state F following the m peak
- Fv
the difference between Fm and Fo
- F'm
maximal F' generated after the m peak by addition of a saturating light pulse
- F'o
the minimal level of F' after the m peak determined by re-oxidising PSII by far-red light
- g1
leaf conductance to CO2 diffusion in the gas phase (mol m–2 s–1)
- g'1
leaf conductance to water vapour diffusion in the gas phase (mol m–2 s–1)
- kc and ko
the Michaelis constants for CO2 and O2, respectively, (µmol mol–1);
- Jmax
the maximum rate of regeneration of rubP (µmol m–2 s–1)
- l
stomatal limitation to CO2 uptake (dimensionless, 0–1)
- LCP
light compensation point of photosynthesis (µmol m–2 s–1)
- oi
the intercellular O2 concentration (mmol mol–1)
- Pi
cytosol inorganic phosphate concentration
- PSI
photosystem I
- PSII
photosystem II
- Q
photon flux (µmol m–2 s–1)
- Qabs
Q absorbed by the leaf
- rubisCO
ribulose 1:5 bisphosphate carboxylase/oxygenase; rubP, ribulose 1:5 bisphosphate; s, projected surface area of a leaf (m2)
- Vc,max
is the maximum rate of carboxylation (µmol m–2 s–1)
- Wc
the rubisCO limited rate of carboxylation (µmol m–2 s1)
- Wj
the electron transport limited rate of regeneration of rubP (µmol m–2 s–1)
- Wp
the inorganic phosphate limited rate of regeneration of rubP (µmol m–2 s–1)
-
absorptance of light (dimensionless, 0–1)
- a
of standard black absorber 1, of leaf
- s
of integrating sphere walls
- , CO2
compensation point of photosynthesis (µmol mol–1)
-
the specificity factor for rubisCO carboxylation (dimensionless)
- ,
convexity of the response of A to Q (dimensionless 0–1)
-
the quantum yield of photosynthesis on an absorbed light basis (A/Qabs; dimensionless)
-
the quantum yield of photosynthesis on an incident light basis (A/Q; dimensionless)
- app
the maximum
- m
the maximum
- m,app
the photochemical efficiency of PSII (dimensionless, 0–1)
- PSII,m
the maximum 相似文献
17.
Yu-Mei Zhou Cun-Guo Wang Shi-Jie Han Xu-Bing Cheng Mai-He Li A-Nan Fan Xiu-Xiu Wang 《Trees - Structure and Function》2011,25(2):163-173
There is, so far, no common conclusion about photosynthetic responses of trees to long-term exposure to elevated CO2. Photosynthesis and specific leaf area (SLA) of 1-year-old and current-year needles in Pinus koraiensis and P. sylvestriformis grown in open-top chambers were measured monthly for consecutive two growing seasons (2006, 2007) after 8–9 years of CO2 enrichment in northeastern China, to better understand species-specific and needle age-related responses to elevated CO2 (500 μmol mol−1 CO2). The light-saturated photosynthetic rates (P
Nsat) increased in both species at elevated CO2, but the stimulation magnitude varied with species and needle age. Photosynthetic acclimation to elevated CO2, in terms of reduced V
cmax (maximum carboxylation rate) and J
max (maximum electron transport rate), was found in P. koraiensis but not in P. sylvestriformis. The photosynthetic parameters (V
cmax, J
max, P
Nsat) measured in different-aged needles within each species responded to elevated CO2 similarly, but elevated CO2 resulted in much pronounced variations of those parameters in current-year needles than in 1-year-old needles within each
species. This result indicated that needle age affects the magnitude but not the patterns of photosynthetic responses to long-term
CO2 enrichment. The present study indicated that different species associated with different physioecological properties responded
to elevated CO2 differently. As global change and CO2 enrichment is more or less a gradual rather than an abrupt process, long-term global change experiments with different plant
species are still needed to character and better predict the global change effects on terrestrial ecosystems. 相似文献
18.
Effects of extreme high temperature,drought and elevated CO2 on photosynthesis of the Mojave Desert evergreen shrub,Larrea tridentata 总被引:4,自引:0,他引:4
Hamerlynck Erik P. Huxman Travis E. Loik Michael E. Smith Stanley D. 《Plant Ecology》2000,146(2):183-193
The interaction of extreme temperature events with future atmospheric CO2 concentrations may have strong impacts on physiological performance of desert shrub seedlings, which during the critical establishment phase often endure temperature extremes in conjunction with pronounced drought. To evaluate the interaction of drought and CO2 on photosynthesis during heat stress, one-year-old Larrea tridentata[DC] Cov. seedlings were exposed to nine days of heat with midday air temperature maxima reaching 53 °C under three atmospheric CO2 concentrations (360, 550 and 700 mol mol–1) and two water regimes (well-watered and droughted). Photosynthetic gas exchange, chlorophyll fluorescence and water potential responses were measured prior to, during and one week following the high temperature stress event. Heat stress markedly decreased net photosynthetic rate (A
net), stomatal conductance (g
s), and the photochemical efficiency of photosystem II (F
v/F
m) in all plants except for well-watered L. tridentata grown in 700 mol mol–1 CO2. A
net and g
s remained similar to pre-stress levels in these plants. In droughted L. tridentata, A
net was ca. 2× (in 550 mol mol–1 CO2) to 3× (in 700 mol mol–1 CO2) higher than in ambient-CO2-grown plants, while g
s and F
v/F
m were similar and low in all CO2 treatments. Following heat stress, g
s in all well-watered plants rose dramatically, exceeding pre-stress levels by up to 100%. In droughted plants, g
s and A
net rose only in plants grown at elevated CO2 following release from heat. This recovery response was strongest at 700 mol mol–1 CO2, which returned to A
net and g
s values similar to pre-heat following several days of recovery. Extreme heat diminished the photosynthetic down-regulation response to growth at elevated CO2 under well-watered conditions, similar to the action of drought. Ambient-CO2-grown L. tridentata did not show significant recovery of photosynthetic capacity (A
\max and CE) after alleviation of temperature stress, especially when exposed to drought, while plants exposed to elevated CO2 appeared to be unaffected. These findings suggest that elevated CO2 could promote photosynthetic activity during critical periods of seedling establishment, and enhance the potential for L. tridentata to survive extreme high temperature events. 相似文献
19.
20.
Time-dependent responses of soil CO2 efflux components to elevated atmospheric [CO2] and temperature in experimental forest mesocosms 总被引:5,自引:0,他引:5
Lin Guanghui Rygiewicz Paul T. Ehleringer James R. Johnson Mark G. Tingey David T. 《Plant and Soil》2001,229(2):259-270
We previously used dual stable isotope techniques to partition soil CO2 efflux into three source components (rhizosphere respiration, litter decomposition, and soil organic matter (SOM) oxidation) using experimental chambers planted with Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings. The components responded differently to elevated CO2 (ambient + 200 mol mol–1) and elevated temperature (ambient + 4 °C) treatments during the first year. Rhizosphere respiration increased most under elevated CO2, and SOM oxidation increased most under elevated temperature. However, many studies show that plants and soil processes can respond to altered climates in a transient way. Herein, we extend our analysis to 2 years to evaluate the stability of the responses of the source components. Total soil CO2 efflux increased significantly under elevated CO2 and elevated temperature in both years (1994 and 1995), but the enhancement was much less in 1995. Rhizosphere respiration increased less under elevated temperature in 1995 compared with 1994. Litter decomposition also tended to increase comparatively less in 1995 under elevated CO2, but was unresponsive to elevated temperature between years. In contrast, SOM oxidation was similar under elevated CO2 in the 2 years. Less SOM oxidation occurred under elevated temperature in 1995 compared with 1994. Our results indicate that temporal variations can occur in CO2 production by the sources. The variations likely involve responses to antecedent physical disruption of the soil and physiological processes. 相似文献