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1.
Blue light induced stomatal opening has been studied by applying a short pulse (~5 to 60 s) of blue light to a background of saturating photosynthetic red photons, but little is known about steady-state stomatal responses. Here we report stomatal responses to blue light at high and low CO2 concentrations. Steady-state stomatal conductance (gs) of C3 plants increased asymptotically with increasing blue light to a maximum at 20% blue (120 μmol m−2 s−1). This response was consistent from 200 to 800 μmol mol−1 atmospheric CO2 (Ca). In contrast, blue light induced only a transient stomatal opening (~5 min) in C4 species above a Ca of 400 μmol mol−1. Steady-state gs of C4 plants generally decreased with increasing blue intensity. The net photosynthetic rate of all species decreased above 20% blue because blue photons have lower quantum yield (moles carbon fixed per mole photons absorbed) than red photons. Our findings indicate that photosynthesis, rather than a blue light signal, plays a dominant role in stomatal regulation in C4 species. Additionally, we found that blue light affected only stomata on the illuminated side of the leaf. Contrary to widely held belief, the blue light-induced stomatal opening minimally enhanced photosynthesis and consistently decreased water use efficiency. 相似文献
2.
Stomatal response to humidity in sugarcane and soybean: effect of vapour pressure difference on the kinetics of the blue light response 总被引:7,自引:2,他引:5
Abstract. The effect of atmospheric humidity on the kinetics of stomatal responses was quantified in gas exchange experiments using sugarcane ( Saccharum spp. hybrid) and soybean ( Glycine max ). Pulses of blue light were used to elicit pulses of stomatal conductance that were mediated by the specific blue light response of guard cells. Kinetic parameters of the conductance response were more closely related to leaf-air vapour pressure difference (VPD) than to relative humidity or transpiration. Increasing VPD significantly accelerated stomatal opening in both sugarcane and soybean, despite an approximately five-fold faster response in sugarcane. In contrast, the kinetics of stomatal recovery (closure) following the pulse were similar in the two species. Acceleration of opening by high VPD was observed even under conditions where soybean exhibited a feedforward response of decreasing transpiration (E) with increasing evaporative demand (VPD). This result suggests that epidermal, rather than bulk leaf, water status mediates the VPD effect on stomatal kinetics. The data are consistent with the hypothesis that increased cpidermal water loss at high VPD decreases the backpressure exerted by neighbouring cells on guard cells. allowing more rapid stomatal opening per unit of guard cell metabolic response to blue light. 相似文献
3.
Root chilling has been shown to inhibit shoot photosynthesis yet the mechanism for such an action is not clearly understood. A study was designed to elucidate the mechanism by which root cooling may affect net photosynthesis. Roots of Artemisia tridentata seedlings were cooled from 20°C to 5°C while their shoot temperature remained at 20°C. This was conducted at two light levels (700 and 1300 μmol m?2 s?1). The time course of shoot net photosynthesis (A), stomatal conductance to water vapor (gs), intercellular CO2 concentration (Ci) and root respiration (Rs) were determined on a whole-plant basis. Root cooling caused a 25% reduction in A at high PPFD, which was preceded by more than 50% reduction of gs and about 10% reduction in Ci. A versus Ci curves for single branches showed no difference between cold and warm soil temperatures, although stomatal conductance was lower for the lower soil temperature. This suggests that a stomatal limitation may have been involved in the inhibition of A. Furthermore, a concomitant decrease of as much as 23% in leaf relative water content (RWC) indicated that root cooling affected stomatal closure due to decreased water supply to the foliage. At lower PPFD, root cooling did not cause a decrease in A of the whole plant despite a moderate drop in gs, Ci and RWC. Cold soil also led to a substantial and rapid reduction in root respiration rate (Rs) regardless of the light level. 相似文献
4.
Stomatal function mediates physiological trade‐offs associated with maintaining a favourable H2O balance in leaf tissues while acquiring CO2 as a photosynthetic substrate. The C3 and C4 species appear to have different patterns of stomatal response to changing light conditions, and variation in this behaviour may have played a role in the functional diversification of the different photosynthetic pathways. In the current study, we used gain analysis theory to characterize the stomatal conductance response to light intensity in nine different C3, C4 and C3‐C4 intermediate species Flaveria species. The response of stomatal conductance (gs) to a change in light intensity represents both a direct (related to a change in incident light intensity, I) and indirect (related to a change in intercellular CO2 concentration, Ci) response. The slope of the line relating the change in gs to Ci was steeper in C4 species, compared with C3 species, with C3‐C4 species having an intermediate response. This response reflects the greater relative contribution of the indirect versus direct component of the gs versus I response in the C4 species. The C3‐C4 species, Flaveria floridana, exhibited a C4‐like response whereas the C3‐C4 species, Flaveria sonorensis and Flaveria chloraefolia, exhibited C3‐like responses, similar to their hypothesized position along the evolutionary trajectory of the development of C4 photosynthesis. There was a positive correlation between the relative contribution of the indirect component of the gs versus I response and water use efficiency when evaluated across all species. Assuming that the C3‐C4 intermediate species reflect an evolutionary progression from fully expressed C3 ancestors, the results of the current study demonstrate an increase in the contribution of the indirect component of the gs versus I response as taxa evolve toward the C4 extreme. The greater relative contribution of the indirect component of the stomatal response occurs through both increases in the indirect stomatal components and through decreases in the direct. Increases in the magnitude of the indirect component may be related to the maintenance of higher water use efficiencies in the intermediate evolutionary stages, before the appearance of fully integrated C4 photosynthesis. 相似文献
5.
Differential coordination of stomatal conductance,mesophyll conductance,and leaf hydraulic conductance in response to changing light across species
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Stomatal conductance (gs) and mesophyll conductance (gm) represent major constraints to photosynthetic rate (A), and these traits are expected to coordinate with leaf hydraulic conductance (Kleaf) across species, under both steady‐state and dynamic conditions. However, empirical information about their coordination is scarce. In this study, Kleaf, gas exchange, stomatal kinetics, and leaf anatomy in 10 species including ferns, gymnosperms, and angiosperms were investigated to elucidate the correlation of H2O and CO2 diffusion inside leaves under varying light conditions. Gas exchange, Kleaf, and anatomical traits varied widely across species. Under light‐saturated conditions, the A, gs, gm, and Kleaf were strongly correlated across species. However, the response patterns of A, gs, gm, and Kleaf to varying light intensities were highly species dependent. Moreover, stomatal opening upon light exposure of dark‐adapted leaves in the studied ferns and gymnosperms was generally faster than in the angiosperms; however, stomatal closing in light‐adapted leaves after darkening was faster in angiosperms. The present results show that there is a large variability in the coordination of leaf hydraulic and gas exchange parameters across terrestrial plant species, as well as in their responses to changing light. 相似文献
6.
Attached leaves of Zea mays were illuminated with monochromatic light, with either the upper or the lower epidermis facing the light source. The mesophyll absorbed between 99.5 and 99.6% of the red or blue light used. An inversion of the light direction therefore caused a 200- to 250-fold change in the quantum flux into each epidermis. This variation in quantum flux did not affect stomatal conductance. Stomatal conductance was however correlated with intercellular CO2 concentration, ci, and the relationship between stomatal conductance and ci appeared also to remain the same if changes in ci were brought about by changes in atmospheric CO2 concentration instead of light. A close inspection of the data showed that stomata of the upper (adaxial) epidermis exhibited a small increase in conductance (<0.1 cm s-1) in response to blue light that was superimposed on the dominating response to ci. 相似文献
7.
Stomatal acclimation over a subambient to elevated CO2 gradient in a C3 /C4 grassland 总被引:2,自引:1,他引:1
H. Maherali C. D. Reid H. W. Polley H. B. Johnson & R. B. Jackson 《Plant, cell & environment》2002,25(4):557-566
An investigation to determine whether stomatal acclimation to [CO2] occurred in C3/C4 grassland plants grown across a range of [CO2] (200–550 µmol mol?1) in the field was carried out. Acclimation was assessed by measuring the response of stomatal conductance (gs) to a range of intercellular CO2 (a gs–Ci curve) at each growth [CO2] in the third and fourth growing seasons of the treatment. The gs–Ci response curves for Solanum dimidiatum (C3 perennial forb) differed significantly across [CO2] treatments, suggesting that stomatal acclimation had occurred. Evidence of non–linear stomatal acclimation to [CO2] in this species was also found as maximum gs (gsmax; gs measured at the lowest Ci) increased with decreasing growth [CO2] only below 400 µmol mol?1. The substantial increase in gs at subambient [CO2] for S. dimidiatum was weakly correlated with the maximum velocity of carboxylation (Vcmax; r2 = 0·27) and was not associated with CO2 saturated photosynthesis (Amax). The response of gs to Ci did not vary with growth [CO2] in Bromus japonicus (C3 annual grass) or Bothriochloa ischaemum (C4 perennial grass), suggesting that stomatal acclimation had not occurred in these species. Stomatal density, which increased with rising [CO2] in both C3 species, was not correlated with gs. Larger stomatal size at subambient [CO2], however, may be associated with stomatal acclimation in S. dimidiatum. Incorporating stomatal acclimation into modelling studies could improve the ability to predict changes in ecosystem water fluxes and water availability with rising CO2 and to understand their magnitudes relative to the past. 相似文献
8.
Stomatal responses to light and humidity in sugarcane: prediction of daily time courses and identification of potential selection criteria 总被引:2,自引:2,他引:0
Abstract Stomatal sensitivities to light and VPD have potential as quantitative selection criteria in programs designed to enhance water-use efficiency of sugarcane and other crops. These responses were characterized using gas exchange techniques and then simulated by a mathematical relationship describing conductance as a function of photon fluence rates and VPD values. The same form of relationship simulated stomatal responses of well-watered greenhouse- and field-grown plants. A comparison between simulated and measured conductance values showed a close correlation, indicating that light and VPD responses of stomata are dominant input signals modulating stomatal conductance in sugarcane. Observed conductance of Hawaiian sugarcane in a commerical production area appeared larger than required to support prevailing rates of carbon assimilation, since predicted intercellular CO2 was greater than required to saturate its C4 photosynthesis. Manipulation of the relationship describing stomatal conductance allowed us to simulate the responses of plants with hypothetically altered stomatal sensitivities to VPD or to light, using micrometeorological data collected in the field. Further simulation indicated that selection for clones with altered stomatal sensitivity to either light or VPD could improve the water-use efficiency of sugarcane without inhibiting current high levels of productivity. 相似文献
9.
R. LEUNING 《Plant, cell & environment》1995,18(4):339-355
Gas-exchange measurements on Eucalyptus grandis leaves and data extracted from the literature were used to test a semi-empirical model of stomatal conductance for CO2 gSc=go+a1A/(cs-I) (1+Ds/Do)] where A is the assimilation rate; Ds and cs are the humidity deficit and the CO2 concentration at the leaf surface, respectively; g0 is the conductance as A → 0 when leaf irradiance → 0; and D0 and a1 are empirical coefficients. This model is a modified version of gsc=a1A hs/cs first proposed by Ball, Woodrow & Berry (1987, in Progress in Photosynthesis Research, Martinus Mijhoff, Publ., pp. 221–224), in which hs is relative humidity. Inclusion of the CO2 compensation point, τ, improved the behaviour of the model at low values of cs, while a hyperbolic function of Ds for humidity response correctly accounted for the observed hyperbolic and linear variation of gsc and ci/cs as a function of Ds, where Ci is the intercellular CO2 concentration. In contrast, use of relative humidity as the humidity variable led to predictions of a linear decrease in gsc and a hyperbolic variation in ci/cs as a function of Ds, contrary to data from E. grandis leaves. The revised model also successfully described the response of stomata to variations in A, Ds and cs for published responses of the leaves of several other species. Coupling of the revised stomatal model with a biochemical model for photosynthesis of C3 plants synthesizes many of the observed responses of leaves to light, humidity deficit, leaf temperature and CO2 concentration. Best results are obtained for well-watered plants. 相似文献
10.
Environmental factors that induce spatial heterogeneity of stomatal conductance, g
s, called stomatal patchiness, also reduce the photochemical capacity of CO2 fixation, yet current methods cannot distinguish between the relative effect of stomatal patchiness and biochemical limitations
on photosynthetic capacity. We evaluate effects of stomatal patchiness and the biochemical capacity of CO2 fixation on the sensitivity of net photosynthetic rate (P
N) to stomatal conductance (g
s), θ (θ = δP
N/g
s). A qualitative model shows that stomatal patchiness increases the sensitivity θ while reduced biochemical capacity of CO2 fixation lowers θ. We used this feature to distinguish between stomatal patchiness and mesophyll impairments in the photochemistry
of CO2 fixation. We compared gas exchange of sunflower (Helianthus annuus L.) plants grown in a growth chamber and fed abscisic acid, ABA (10−5 M), for 10 d with control plants (-ABA). P
N and g
s oscillated more frequently in ABA-treated than in control plants when the leaves were placed into the leaf chamber and exposed
to a dry atmosphere. When compared with the initial CO2 response measured at the beginning of the treatment (day zero), both ABA and control leaves showed reduced P
N at particular sub-stomatal CO2 concentration (c
i) during the oscillations. A lower reduction of P
N at particular g
s indicated overestimation of c
i due to stomatal patchiness and/or omitted cuticular conductance, g
c. The initial period of damp oscillation was characterised by inhibition of chloroplast processes while stomatal patchiness
prevailed at the steady state of gas exchange. The sensitivity θ remained at the original pre-treatment values at high g
s in both ABA and control plants. At low g
s, θ decreased in ABA-treated plants indicating an ABA-induced impairment of chloroplast processes. In control plants, g
c neglected in the calculation of g
s was the likely reason for apparent depression of photosynthesis at low g
s.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
Imaging of photochemical yield of photosystem II (PSII) computed from leaf chlorophyll fluorescence images and gas-exchange measurements were performed on Rosa rubiginosa leaflets during abscisic acid (ABA) addition. In air ABA induced a decrease of both the net CO2 assimilation (An) and the stomatal water vapor conductance (gs). After ABA treatment, imaging in transient nonphotorespiratory conditions (0.1% O2) revealed a heterogeneous decrease of PSII photochemical yield. This decline was fully reversed by a transient high CO2 concentration (7400 μmol mol−1) in the leaf atmosphere. It was concluded that ABA primarily affected An by decreasing the CO2 supply at ribulose-1,5-bisphosphate carboxylase/oxygenase. Therefore, the An versus intercellular mole fraction (Ci) relationship was assumed not to be affected by ABA, and images of Ci and gs were constructed from images of PSII photochemical yield under nonphotorespiratory conditions. The distribution of gs remained unimodal following ABA treatment. A comparison of calculations of Ci from images and gas exchange in ABA-treated leaves showed that the overestimation of Ci estimated from gas exchange was only partly due to heterogeneity. This overestimation was also attributed to the cuticular transpiration, which largely affects the calculation of the leaf conductance to CO2, when leaf conductance to water is low. 相似文献
12.
Effects of patchy stomatal closure on gas exchange measurements following abscisic acid treatment 总被引:9,自引:5,他引:4
K. A. MOTT 《Plant, cell & environment》1995,18(11):1291-1300
Gas exchange data and images of leaf fluorescence were collected concurrently as stomata responded to abscisic acid (ABA) application. When 10?5kmolm?3 ABA was applied to the transpiration stream in a short pulse, stomatal conductance (gs), photosynthesis (A) and intercellular CO2 concentration (Ci) decreased rapidly after a short lag period and became approximately constant after 2h. There was an apparent reduction in the A versus c1 relationship as stomata closed, but the data returned to the A versus C1 curve while stomatal conductance was constant or slowly rising during the second hour after ABA treatment. Larger amounts of ABA administered during the pulse caused larger deviations from the A versus c1 relationship. When 10?7kmolm?3 ABA was applied continuously through the transpiration stream, gs, A and Ci decreased, but there was no substantial deviation from the A versus c{ curve. Fluorescence images were patchy as stomata closed for all experiments, but became slowly more uniform during the time that gas exchange was returning to the A versus Cj curve. The distribution of con-ductance among patches was not bimodal, and larger devi-ations from the A versus ct curve had greater ranges of pixel values and more pixel values representing low values of Cj during stomatal closure than did experiments show-ing small or no deviation. Estimates of A and gs from fluo-rescence images compared favourably with measured val-ues in most cases, suggesting that the patchy distributions of fluorescence were caused by patchy distributions of stomatal conductance and that apparent reductions in the A versus ct relationship were the result of these patchy stomatai distributions and not direct effects of ABA on mesophyll functioning. The data show that stomatal patches can be temporary and that patchiness may not be reflected in gas exchange data if the range of stomatal con-ductances is not large. These observations may explain some of the discrepancies among previous studies concerning the effect of ABA on the A versus Ci relationship. 相似文献
13.
J.-H. Li W. A. Dugas† G. J. Hymus D. P. Johnson C. R. Hinkle‡ B. G. Drake B. A. Hungate§ 《Global Change Biology》2003,9(1):96-105
Elevated atmospheric carbon dioxide (Ca) usually reduces stomatal conductance, but the effects on plant transpiration in the field are not well understood. Using constant‐power sap flow gauges, we measured transpiration from Quercus myrtifolia Willd., the dominant species of the Florida scrub‐oak ecosystem, which had been exposed in situ to elevated Ca (350 µmol mol ? 1 above ambient) in open‐top chambers since May 1996. Elevated Ca reduced average transpiration per unit leaf area by 37%, 48% and 49% in March, May and October 2000, respectively. Temporarily reversing the Ca treatments showed that at least part of the reduction in transpiration was an immediate, reversible response to elevated Ca. However, there was also an apparent indirect effect of Ca on transpiration: when transpiration in all plants was measured under common Ca, transpiration in elevated Ca‐grown plants was lower than that in plants grown in normal ambient Ca. Results from measurements of stomatal conductance (gs), leaf area index (LAI), canopy light interception and correlation between light and gs indicated that the direct, reversible Ca effect on transpiration was due to changes in gs caused by Ca, and the indirect effect was caused mainly by greater self‐shading resulting from enhanced LAI, not from stomatal acclimation. By reducing light penetration through the canopy, the enhanced self‐shading at elevated Ca decreased stomatal conductance and transpiration of leaves at the middle and bottom of canopy. This self‐shading mechanism is likely to be important in ecosystems where LAI increases in response to elevated Ca. 相似文献
14.
Twin Cays (Belize) is a highly oligotrophic mangrove archipelago dominated by Rhizophora mangle L. Ocean‐fringing trees are 3–7 m tall with a leaf area index (LAI) of 2.3, whereas in the interior, dwarf zone, trees are 1.5 m or less, and the LAI is 0.7. P‐fertilization of dwarf trees dramatically increases growth. As a partial explanation of these characteristics, it was hypothesized that differences in stature and growth rates would reflect differences in leaf photosynthetic capacity, as determined by the photochemical and biochemical characteristics at the chloroplast level. Gas exchange and chlorophyll fluorescence were used to compare photosynthesis of dwarf, fringe and fertilized trees. Regardless of zonation or treatment, net CO2 exchange (A) and photosynthetic electron transport were light saturated at less than 500 µmol photons m?2 s?1, and low‐light quantum efficiencies were typical for healthy C3 plants. On the other hand, light‐saturated A was linearly related to stomatal conductance (gs), with seasonal, zonal and treatment differences in photosynthesis corresponding linearly to differences in the mean gs. Overall, photosynthetic capacity appeared to be co‐regulated with stomatal conductance, minimizing the variability of Ci at ambient CO2 (and hence, Ci/Ca). Based on the results of in vitro assays, regulation of photosynthesis in R. mangle appeared to be accomplished, at least in part, by regulation of Rubisco activity. 相似文献
15.
Frederick C. Meinzer 《Oecologia》1982,54(2):270-274
Summary Attached twigs of young Pseudotsuga menziesii (Mirb.) Franco plants were subjected to variations in irradaince. Stomatal responsiveness to irradiance, measured in an open type gas exchange system, varied seasonally. During the autumn and winter, stomatal conductance was relatively unresponsive to changes in irradiance, but during the summer stomatal conductance decreased in response to reduced irradiance. The summer stomatal response to irradiance was such that a nearly constant ratio of stomatal conductance to net photosynthesis was maintained as irradiance was varied. This caused intercellular CO2 concentration (c
i) and water use efficiency (net CO2 uptake/transpiration) to also remain relatively constant. At constant irradiance, stomatal conductance was relatively insensitive to experimentally-induced changes in c
i. This, and the observation that c
i remained relatively constant as irradiance was varied, suggest that changes in c
i played a minor role in mediating the stomatal response to light.The ecological significance of the seasonal changes in stomatal response to light is discussed. 相似文献
16.
Background and Aims
Leaf hydraulic properties are strongly linked with transpiration and photosynthesis in many species. However, it is not known if gas exchange and hydraulics will have co-ordinated responses to climate change. The objective of this study was to investigate the responses of leaf hydraulic conductance (Kleaf) in Glycine max (soybean) to growth at elevated [CO2] and increased temperature compared with the responses of leaf gas exchange and leaf water status.Methods
Two controlled-environment growth chamber experiments were conducted with soybean to measure Kleaf, stomatal conductance (gs) and photosynthesis (A) during growth at elevated [CO2] and temperature relative to ambient levels. These results were validated with field experiments on soybean grown under free-air elevated [CO2] (FACE) and canopy warming.Key results
In chamber studies, Kleaf did not acclimate to growth at elevated [CO2], even though stomatal conductance decreased and photosynthesis increased. Growth at elevated temperature also did not affect Kleaf, although gs and A showed significant but inconsistent decreases. The lack of response of Kleaf to growth at increased [CO2] and temperature in chamber-grown plants was confirmed with field-grown soybean at a FACE facility.Conclusions
Leaf hydraulic and leaf gas exchange responses to these two climate change factors were not strongly linked in soybean, although gs responded to [CO2] and increased temperature as previously reported. This differential behaviour could lead to an imbalance between hydraulic supply and transpiration demand under extreme environmental conditions likely to become more common as global climate continues to change. 相似文献17.
LISA AUCHINCLOSS HSIEN M. EASLON DIEDRE LEVINE LISA DONOVAN JAMES H. RICHARDS 《Plant, cell & environment》2014,37(6):1364-1370
Most C3 plant species have partially open stomata during the night especially in the 3–5 h before dawn. This pre‐dawn stomatal opening has been hypothesized to enhance early‐morning photosynthesis (A) by reducing diffusion limitations to CO2 at dawn. We tested this hypothesis in cultivated Helianthus annuus using whole‐shoot gas exchange, leaf level gas exchange and modelling approaches. One hour pre‐dawn low‐humidity treatments were used to reduce pre‐dawn stomatal conductance (g). At the whole‐shoot level, a difference of pre‐dawn g (0.40 versus 0.17 mol m?2 s?1) did not significantly affect A during the first hour after dawn. Shorter term effects were investigated with leaf level gas exchange measurements and a difference of pre‐dawn g (0.10 versus 0.04 mol m?2 s?1) affected g and A for only 5 min after dawn. The potential effects of a wider range of stomatal apertures were explored with an empirical model of the relationship between A and intercellular CO2 concentration during the half‐hour after dawn. Modelling results demonstrated that even extremely low pre‐dawn stomatal conductance values have only a minimal effect on early‐morning A for a few minutes after dawn. Thus, we found no evidence that pre‐dawn stomatal opening enhances A. 相似文献
18.
Enhanced Photosynthesis and Stomatal Conductance of Pima Cotton (Gossypium barbadense L.) Bred for Increased Yield 总被引:5,自引:0,他引:5
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Yield of Pima cotton (Gossypium barbadense L.) has tripled over the last 40 years with the development of new cultivars. Six genetic lines representing successive stages in the breeding process (one primitive noncultivated accession, four cultivars with release dates from 1949 to 1983, and one unreleased breeding line) were grown in a greenhouse, and their gas exchange properties were compared. Among the cultivated types, genetic advances were closely associated with increasing single-leaf photosynthetic rate (A) and stomatal conductance (gs), especially in the morning. The A and gs of the primitive line approached those of the cultivated types early in the morning, but were much lower for the rest of the day. In both morning and afternoon, A was correlated with gs across genotypes but was not correlated with leaf thickness, concentrations of chlorophyll or starch, or intercellular CO2 concentration (ci). In the oldest cultivar, the relationship of A to ci did not change between morning and afternoon. In the two most recent lines, the slopes of the A:ci curves at limiting ci exceeded that of the oldest cultivar by 25 to 50% in the morning, but the differences were much smaller in the afternoon. The maximum A of the newer lines at high ci exceeded that of the oldest cultivar only in the morning. Breeding for increasing yield has enhanced the photosynthetic capacity and stomatal conductance of Pima cotton and altered the diurnal regulation of photosynthesis. 相似文献
19.
Acclimation of photosynthesis to increasing atmospheric CO2: The gas exchange perspective 总被引:9,自引:0,他引:9
Rowan F. Sage 《Photosynthesis research》1994,39(3):351-368
The nature of photosynthetic acclimation to elevated CO2 is evaluated from the results of over 40 studies focusing on the effect of long-term CO2 enrichment on the short-term response of photosynthesis to intercellular CO2 (the A/Ci response). The effect of CO2 enrichment on the A/Ci response was dependent on growth conditions, with plants grown in small pots (< 5 L) or low nutrients usually exhibiting a reduction of A at a given Ci, while plants grown without nutrient deficiency in large pots or in the field tended to exhibit either little reduction or an enhancement of A at a given Ci following a doubling or tripling of atmospheric CO2 during growth. Using theoretical interpretations of A/Ci curves to assess acclimation, it was found that when pot size or nutrient deficiency was not a factor, changes in the shape of A/Ci curves which are indicative of a reallocation of resources within the photosynthetic apparatus typically were not observed. Long-term CO2 enrichment usually had little effect or increased the value of A at all Ci. However, a minority of species grown at elevated CO2 exhibited gas exchange responses indicative of a reduced amount of Rubisco and an enhanced capacity to metabolize photosynthetic products. This type of response was considered beneficial because it enhanced both photosynthetic capacity at high CO2 and reduced resource investment in excessive Rubisco capacity. The ratio of intercellular to ambient CO2 (the Ci/Ca ratio) was used to evaluate stomatal acclimation. Except under water and humidity stress, Ci/Ca exhibited no consistent change in a variety of C3 species, indicating no stomatal acclimation. Under drought or humidity stress, Ci/Ca declined in high-CO2 grown plants, indicating stomata will become more conservative during stress episodes in future high CO2 environments.Abbreviations A
net CO2 assimilation rate
- Ci (Ca)
intercellular (ambient) partial pressure of CO2
- operational Ci
intercellular partial pressure of CO2 at a given ambient partial pressure of CO2
- gs
stomatal conductance
- normal CO2
current atmospheric mole fraction of CO2 (330 to 355 mol mol–1)
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase 相似文献
20.
The effect of D-(+)-mannose, inorganic phosphate (Pi) and mannose-6-phosphate on net mesophyll CO2 assimilation rate (A) and stomatal conductance (gs) of wheat (Triticum aestivum L.) leaves was studied. The compounds were supplied through the transpiration stream of detached leaves from plants grown in sand in growth cabinets or glasshouses, with different concentrations of Pi (0.25, 1.0 and 4.0 mM) supplied during growth. In all cases, 10 mM D-(+)mannose caused 40–60% reduction of A within 30 min, though the time courses differed for flag leaves and the sixth leaf on the mainstem of glasshouse- and cabinet-grown plants. D-(+)Mannose had a similar effect on A in leaves having a fourfold range in total phosphate content. Effects of D-(+)mannose in reducing gs were always slower than on A. When the CO2 concentration in the leaf chamber was adjusted to maintain intercellular CO2 concentration (Ci) constant as A declined after mannose supply, gs still declined indicating that stomatal closure was not caused by changing Ci. Supplying mannose-6-phosphate at 10 and 1 mM and Pi at 5 and 10 mM concentrations caused rapid reductions in gs and also direct reductions in A. The observed effects of mannose and Pi on assimilation are consistent with the proposed regulatory role of cytoplasmic Pi in determining mesophyll carbon assimilation that has been derived previously using leaf discs, protoplasts and chloroplasts.Abbreviations and symbols A
net mesophyll CO2-assimilation rate
- Ca, Ci
external (assimilation-chamber) and intercellular CO2 concentration, respectively
- gs
stomatal conductance
- Man6P
mannose-6-phosphate
- Pi
orthophosphate 相似文献