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1.
The oxygen requirement for stomatal opening in maize plants ( Zea mays L. hybrid INRA 508) was studied at different CO2 concentrations and light intensities. In the absence of CO2, stomatal opening always required O2, but this requirement decreased with increasing light intensity. In darkness, the lowest O2 partial pressure needed to obtain a weak stomatal movement was about 50 Pa. This value was lowered to ca 10 Pa in light (320 μmol m−2 s−1).
On the other hand. in the absence of O2, CO2enabled stomatal opening to occur in the light, presumably due to the evolved photosynthetic O2. Thus, CO2, which generally reduced stomatal aperture, could induce stomatal movement in anoxia and light. The effect of CO2 on stomatal opening was closely dependent on O2 concentration and light intensity. Stomatal aperture appeared CO2-independent at an O2 partial pressure which was dependent on light intensity and was about 25 Pa at 320 umol m−2 s−1.
The presence of a plasmalemma oxidase, in addition to mitochondrial oxidase, might explain the differences in the O2 requirement at various light intensities. The possible involvement of such a system in relation to the effect of CO2 is discussed.  相似文献   

2.

A , carbon assimilation rate
ABA, abscisic acid
Ci , intercellular space CO2 concentration
g , leaf conductance
WUE, water use efficiency

Carbon dioxide and abscisic acid (ABA) are two major signals triggering stomatal closure. Their putative interaction in stomatal regulation was investigated in well-watered air-grown or double CO2-grown Arabidopsis thaliana plants, using gas exchange and epidermal strip experiments. With plants grown in normal air, a doubling of the CO2 concentration resulted in a rapid and transient drop in leaf conductance followed by recovery to the pre-treatment level after about two photoperiods. Despite the fact that plants placed in air or in double CO2 for 2 d exhibited similar levels of leaf conductance, their stomatal responses to an osmotic stress (0·16–0·24 MPa) were different. The decrease in leaf conductance in response to the osmotic stress was strongly enhanced at elevated CO2. Similarly, the drop in leaf conductance triggered by 1 μ M ABA applied at the root level was stronger at double CO2. Identical experiments were performed with plants fully grown at double CO2. Levels of leaf conductance and carbon assimilation rate measured at double CO2 were similar for air-grown and elevated CO2-grown plants. An enhanced response to ABA was still observed at high CO2 in pre-conditioned plants. It is concluded that: (i) in the absence of stress, elevated CO2 slightly affects leaf conductance in A. thaliana ; (ii) there is a strong interaction in stomatal responses to CO2 and ABA which is not modified by growth at elevated CO2.  相似文献   

3.
The responses of individual stomata to CO2 concentrations ranging from 0 to 900 μmol mol−1 air were analysed in Ipomoea pes-caprae L. Sweet (Convolvulaceae). The stomata were directly observed using a measurement system that permitted continuous observation of stomatal movement under controlled light and CO2 conditions. A CO2 concentration of 350 μmol mol−1 or higher induced stomatal closure, whereas concentrations below 350 μmol mol−1 did not. The time lag before stomatal closure decreased with increasing CO2 concentration, as did the steady-state aperture of the stomata after a change in CO2 concentration. However, the rate of stomatal closure increased with increasing CO2 concentration. Therefore, not only the stomatal closure rate but also the time from the CO2 concentration change to the beginning of stomatal closure changed with increasing CO2 concentration. These results suggest that atmospheric CO2 may be the stimulus for the closure of guard cells. No significant differences were observed between adaxial and abaxial stomata in terms of their responses to CO2. However, heterogeneous responses were detected between neighbouring stomata on each leaf surface.  相似文献   

4.
Stomatal behaviour, photosynthesis and transpiration under rising CO2   总被引:2,自引:2,他引:0  

Definitions of the variables used and the units are given in Table 1

The literature reports enormous variation between species in the extent of stomatal responses to rising CO2. This paper attempts to provide a framework within which some of this diversity can be explained. We describe the role of stomata in the short-term response of leaf gas exchange to increases in ambient CO2 concentration by developing the recently proposed stomatal model of Jarvis & Davies (1998 ). In this model stomatal conductance is correlated with the functioning of the photosynthetic system so that the effects of increases in CO2 on stomata are experienced through changes in the rate of photosynthesis in a simple and mechanistically transparent way. This model also allows us to consider the effects of evaporative demand and soil moisture availability on stomatal responses to photosynthesis and therefore provides a means of considering these additional sources of variation. We emphasize that the relationship between the rate of photosynthesis and the internal CO2 concentration and also drought will have important effects on the relative gains to be achieved under rising CO2.  

  Table 1 . Abbreviations  相似文献   


5.
The stomatal response to CO2 is linked to changes in guard cell zeaxanthin*   总被引:4,自引:2,他引:2  
The mechanisms mediating CO2 sensing and light–CO2 interactions in guard cells are unknown. In growth chamber-grown Vicia faba leaves kept under constant light (500 μ mol m–2 s–1) and temperature, guard cell zeaxanthin content tracked ambient [CO2] and stomatal apertures. Increases in [CO2] from 400 to 1200 cm3 m–3 decreased zeaxanthin content from 180 to 80 mmol mol–1 Chl and decreased stomatal apertures by 7·0 μ m. Changes in zeaxanthin and aperture were reversed when [CO2] was lowered. Guard cell zeaxanthin content was linearly correlated with stomatal apertures. In the dark, the CO2-induced changes in stomatal aperture were much smaller, and guard cell zeaxanthin content did not change with chamber [CO2]. Guard cell zeaxanthin also tracked [CO2] and stomatal aperture in illuminated stomata from epidermal peels. Dithiothreitol (DTT), an inhibitor of zeaxanthin formation, eliminated CO2-induced zeaxanthin changes in guard cells from illuminated epidermal peels and reduced the stomatal CO2 response to the level observed in the dark. These data suggest that CO2-dependent changes in the zeaxanthin content of guard cells could modulate CO2-dependent changes of stomatal apertures in the light while a zeaxanthin-independent CO2 sensing mechanism would modulate the CO2 response in the dark.  相似文献   

6.
To investigate the diurnal variation of stomatal sensitivity to CO2, stomatal response to a 30 min pulse of low CO2 was measured four times during a 24 h time-course in two Crassulacean acid metabolism (CAM) species Kalanchoe daigremontiana and Kalanchoe pinnata , which vary in the degree of succulence, and hence, expression and commitment to CAM. In both species, stomata opened in response to a reduction in p CO2 in the dark and in the latter half of the light period, and thus in CAM species, chloroplast photosynthesis is not required for the stomatal response to low p CO2. Stomata did not respond to a decreased p CO2 in K. daigremontiana in the light when stomata were closed, even when the supply of internal CO2 was experimentally reduced. We conclude that stomatal closure during phase III is not solely mediated by high internal p CO2, and suggest that in CAM species the diurnal variability in the responsiveness of stomata to p CO2 could be explained by hypothesizing the existence of a single CO2 sensor which interacts with other signalling pathways. When not perturbed by low p CO2, CO2 assimilation rate and stomatal conductance were correlated both in the light and in the dark in both species.  相似文献   

7.
Variation in stomatal development and physiology of mature leaves from Alnus glutinosa plants grown under reference (current ambient, 360 μmol mol−1 CO2) and double ambient (720 μmol mol−1 CO2) carbon dioxide (CO2) mole fractions is assessed in terms of relative plant growth, stomatal characters (i.e. stomatal index and density) and leaf photosynthetic characters. This is the first study to consider the effects of elevated CO2 concentration on the distribution of stomata and epidermal cells across the whole leaf and to try to ascertain the cause of intraleaf variation. In general, a doubling of the atmospheric CO2 concentration enhanced plant growth and significantly increased stomatal index. However, there was no significant change in relative stomatal density. Under elevated CO2 concentration there was a significant decrease in stomatal conductance and an increase in assimilation rate. However, no significant differences were found for the maximum rate of carboxylation ( V cmax) and the light saturated rate of electron transport ( J max) between the control and elevated CO2 treatment.  相似文献   

8.
Implications of non-uniform stomatal closure on gas exchange calculations   总被引:5,自引:4,他引:1  
Abstract. This paper discusses the consequences of non-uniform (= patchwise) stomatal closure on the estimation of gas exchange parameters. The estimation of the partial pressure of internal CO2 (ci) appears to be little sensitive to complete non-uniform stomatal closure. During the process of closure of these patches, however, a lower ci will be calculated. For gas exchange measurements done at low wind speeds, it can be shown that an error is made in the partitioning of the total vapour transfer resistance into boundary layer and stomatal resistance. This error influences the calculated total transfer resistance of gases other than water vapour (e.g. CO2). The apparent negative internal gas concentrations that have sometimes been found in fumigation experiments with SO2 can possibly be explained by this error.  相似文献   

9.
The cellular basis of guard cell sensing of rising CO2   总被引:5,自引:1,他引:4  
Numerous studies conducted on both whole plants and isolated epidermes have documented stomatal sensitivity to CO2. In general, CO2 concentrations below ambient stimulate stomatal opening, or an inhibition of stomatal closure, while CO2 concentrations above ambient have the opposite effect. The rise in atmospheric CO2 concentrations which has occurred since the industrial revolution, and which is predicted to continue, will therefore alter rates of transpirational water loss and CO2 uptake in terrestrial plants. An understanding of the cellular basis for guard cell CO2 sensing could allow us to better predict, and perhaps ultimately to manipulate, such vegetation responses to climate change. However, the mechanisms by which guard cells sense and respond to the CO2 signal remain unknown. It has been hypothesized that cytosolic pH and malate levels, cytosolic Ca2+ levels, chloroplastic zeaxanthin levels, or plasma-membrane anion channel regulation by apoplastic malate are involved in guard cell perception and response to CO2. In this review, these hypotheses are discussed, and the evidence for guard cell acclimation to prevailing CO2 concentrations is also considered.  相似文献   

10.
We investigated the relationship between stomatal frequency and a range of atmospheric CO2 concentrations ([CO2]atm) in Betula pubescens and Pinus sylvestris , two important boreal trees in Scandinavia. If strong relationships exist, they can be used to reconstruct past [CO2]atm from stomatal frequency of fossil Betula and Pinus leaves. Responses of epidermal characters (stomatal density (SD), epidermal cell density (ED), stomatal index (SI)) to different CO2 concentrations were investigated utilising (1) the lower partial pressure of CO2 at increasing altitudes for B. pubescens , and in herbarium specimens of B. pubescens and P. sylvestris collected during the post-industrial rise of [CO2]atm from c. 280 ppmv to c. 360 ppmv in 1997 and (2) concentrations (560 ppmv) and temperatures (3° summer) above present day in the CLIMEX greenhouse experiment. All the results show no clear relationship between SD or SI and [CO2] atm for either B. pubescens or P. sylvestris. Most likely there are stronger genetically and environmentally induced factors that affect the development of the leaves. Problems with collecting representative samples from herbarium specimens are discussed. Since the effects of changes in [CO2]atm cannot be statistically modelled, B. pubescens and P. sylvestris are not suitable for reconstructing past atmospheric CO2 concentrations from fossil leaves using stomatal density or stomatal index  相似文献   

11.
Major fluctuations in the concentrations of atmospheric CO2 and O2, are predicted by historical long-term carbon and oxygen cycle models of atmospheric evolution and will have impacted directly on past climates, plant function and evolutionary processes. Here, palaeobotanical evidence is presented from the stomatal density record of fossil leaves spanning the past 400 Myr supporting the predicted changes in atsmopheric CO2. Evidence from experiments on plants exposed to long-term high CO2, environments and the newly-assembled fossil data indicate the potential for genetic modification of stomatal characters. The influence of the changes in fossil stomatal characteristics and atmospheric composition on the rates of leaf gas exchange over the course of land plant evolution has been investigated through modelling. Three contrasting eras of plain water economics emerge in the Devonian (high), Carboniferous (low) and from the Upper Jurassic to the present-day (high but declining). These patterns of change result from structural changes of the leaves and the impact of atmospheric CO2, and O2, concentrations on RuBisCo function and are consistent with the fossil evidence of sequential appearances of novel plant anatomical changes. The modelling approach is tested by comparing predicted leaf stable carbon isotope ratios with those measured on fossil plant and organic material. Viewed in a geological context, current and future increases in the concentration of atmospheric CO2, might be considered as restoring plant function to that more typically experienced by plants over the majority of their evolutionary history.  相似文献   

12.
Abstract. A portable apparatus has been constructed to measure simultaneously the quantum yield of CO2 assimilation, light absorption, chlorophyll fluorescence emission and water vapour exchange of attached intact leaves in the field. The core of the instrument is a light-integrating spherical leaf chamber which includes ports for a light source, photosynthetically active radiation sensor, fluorescence probes and gas inlet and outlet manifolds. Measurement of the quantum flux inside the empty chamber and with a leaf present allows determination of leaf absorptance. An open gas exchange system is employed using an infra-red analyser to measure leaf CO2 exchange. Using a DC white light source the quantum yield of CO2 assimilation based on absorbed light (φabs) may be determined rapidly in either ambient air or artificial gas mixtures. Inclusion of capacitance humidity probes into the gas inlet and outlet ports allows simultaneous determination of water vapour exchange and subsequent estimation of stomatal conductance to CO2 and intercellular CO2 concentration. Measurement of fluorescence emission by the sample leaf exposed to white light is achieved by a modulated fluorescence detection system. In addition to determination of the minimal, maximal and variable fluorescence levels, a further analysis allows the photochemical and non-photochemical components of fluorescence quenching, to be estimated. The theory and design of this apparatus is described in detail. The use of the apparatus in the field is demonstrated through a study of the photosynthetic performance of a maize and bean crop during the growing season and by analysis of the photosynthetic performance of crops subjected to nitrogen-stress and a herbicide treatment.  相似文献   

13.
Two Italian CO2 springs allowed us to study the long-term effect of a 350–2600 μ mol mol–1 increase in CO2 concentrations on the surface structures of leaves of Quercus ilex L. Carbon dioxide increased the quantity of cuticular waxes, above an apparent threshold of 750 μ mol mol–1 CO2. Leaf wettability was not modified by CO2 concentrations. Reduction in stomatal frequency was observable up to 750 μ mol mol–1 CO2, the slope being almost the same as that estimated for the increase in CO2 concentration from pre-industrial times to the present. At higher concentrations, CO2 seemed to exert no more impact on stomatal frequency.  相似文献   

14.
Within the genus Polygonum a large variation was found between species with regard to stomatal number, gas phase resistance, intracellular resistance and dark respiration. Interspecific variation in CO2 compensation concentration and intercellular CO2 concentration at constant external concentration were comparatively small. Correlations were found between stomatal number and gas phase resistance, stomatal number and Γ, and Γ and the product of dark respiration rate and intracellular resistance. The influence of dark respiration and stomatal number on photosynthetic gas exchange is discussed. It was concluded that dark respiration in light was enhanced by 22% as a mean value in 9 Polygonum species and by 62% in Polygonum lapathifolium .  相似文献   

15.
Carbon dioxide induces increases in guard cell cytosolic free calcium   总被引:10,自引:0,他引:10  
The hypothesis that increases in cytosolic free calcium ([Ca2+]i) are a component of the CO2 signal transduction pathway in stomatal guard cells of Commelina communis has been investigated. This hypothesis was tested using fura-2 fluorescence ratio photometry to measure changes in guard cell [Ca2+]i in response to challenge with 700 µl l−1 CO2. Elevated CO2 induced increases in guard cell [Ca2+]i which were similar to those previously reported in response to abscisic acid. [Ca2+]i returned to resting values following removal of the CO2 and further application of CO2 resulted in a second increase in [Ca2+]i. This demonstrated that the CO2-induced increases in [Ca2+]i were stimulus dependent. Removal of extracellular calcium both prevented the CO2-induced increase in [Ca2+]i and inhibited the associated reduction in stomatal aperture. These data suggest that Ca2+ acts as a second messenger in the CO2 signal transduction pathway and that an increase in [Ca2+]i may be a requirement for the stomatal response to CO2.  相似文献   

16.
Evolutionary responses of stomatal density to global CO2 change   总被引:3,自引:0,他引:3  
Stomatal density is known to respond to CO2 levels during leaf development. Current interest in the increasing concentration of atmospheric CO2 has stimulated much experimentation on the responses of plants to relatively short-term exposure in artificially high CO2 levels. Attempts to extrapolate from short-term to long-term responses raise fundamental questions concerning evolutionary change in response to rising global CO2 levels. We consider the improved water use efficiency observed under elevated CO2 levels to be the main driving force of natural selection affecting the genotypic component controlling stomatal density. Whether a response is merely phenotypic or becomes incorporated into the genotype depends on two factors: (i) the time scale of exposure and (ii) the generation time of a species. Measurements of stomatal density on fossil leaves of Salix herbacea through a glacial cycle covering the last 140000 years have shown a decrease in stomatal density in response to the rising CO2 levels of this period. This accords with the shorter-term observations on leaves of trees seen in herbarium specimens where the stomatal density has decreased in response to the rising CO2 levels of the last 200 years. The results indicate that natural selection over the 140000-year period may have favoured a similar response to that shown by trees phenotypically over the last 200 years. Since there is now some evidence for the genetic control of stomatal density, the role of natural selection affecting it must be considered when translating responses from short-term experiments to predict how stomatal density will be affected by long-term climatic and atmospheric change.  相似文献   

17.
Stomatal density (SD) and stomatal conductance ( g s) can be affected by an increase of atmospheric CO2 concentration. This study was conducted on 17 species growing in a naturally enriched CO2 spring and belonging to three plant communities. Stomatal conductance, stomatal density and stomatal index (SI) of plants from the spring, which were assumed to have been exposed for generations to elevated [CO2], and of plants of the same species collected in a nearby control site, were compared. Stomatal conductance was significantly lower in most of the species collected in the CO2 spring and this indicated that CO2 effects on g s are not of a transitory nature but persist in the long term and through plant generations. Such a decrease was, however, not associated with changes in the anatomy of leaves: SD was unaffected in the majority of species (the decrease was only significant in three out of the 17 species examined), and also SI values did not vary between the two sites with the exception of two species that showed increased SI in plants grown in the CO2-enriched area. These results did not support the hypothesis that long-term exposure to elevated [CO2] may cause adaptive modification in stomatal number and in their distribution.  相似文献   

18.
The effect of long-term water stress on photosynthetic carbon metabolism in Casuarina equisetifolia Forst. & Forst. was analysed by measuring CO2 assimilation, stomatal conductance, the quantum yield of photosystem II ( Φ PSII), enzyme activities, and the levels of photosynthetic intermediates and carbohydrates. CO2 assimilation decreased under water stress while the intercellular CO2 concentration ( C i) as estimated by gas exchange measurements remained high. However, the estimates of C i from measurements of Φ PSII suggest that the decrease in photosynthesis can be explained in terms of stomatal closure. Water stress decreased total stromal fructose-1,6-bisphosphatase activity and did not alter the activities and activation states of ribulose bisphosphate carboxylase oxygenase and NADP-dependent malate dehydrogenase (NADP-MDH). The concentration of photosynthetic metabolites, glucose, fructose and sucrose decreased, whereas starch concentrations increased under drought conditions.  相似文献   

19.
We developed and applied an ecosystem-scale model that calculated leaf CO2 assimilation, stomatal conductance, chloroplast CO2 concentration and the carbon isotope composition of carbohydrate formed during photosynthesis separately for sunlit and shaded leaves within multiple canopy layers. The ecosystem photosynthesis model was validated by comparison to leaf-level gas exchange measurements and estimates of ecosystem-scale photosynthesis from eddy covariance measurements made in a coastal Douglas-fir forest on Vancouver Island. A good agreement was also observed between modelled and measured δ 13C values of ecosystem-respired CO2 ( δ R). The modelled δ R values showed strong responses to variation in photosynthetic photon flux density (PPFD), air temperature, vapour pressure deficit (VPD) and available soil moisture in a manner consistent with leaf-level studies of photosynthetic 13C discrimination. Sensitivity tests were conducted to evaluate the effect of (1) changes in the lag between the time of CO2 fixation and the conversion of organic matter back to CO2; (2) shifts in the proportion of autotrophic and heterotrophic respiration; (3) isotope fractionation during respiration; and (4) environmentally induced changes in mesophyll conductance, on modelled δ R values. Our results indicated that δ R is a good proxy for canopy-level C c/ C a and 13C discrimination during photosynthetic gas exchange, and therefore has several applications in ecosystem physiology.  相似文献   

20.
Artificial chalk grassland swards were exposed to either ambient air or air enriched to 600 μ mol mol–1 CO2, using free-air CO2 enrichment technology, and subjected to an 8 week simulated grazing regime. After 14 months of treatment, ribulose-1,5-bisphosphate carboxylase (Rubisco) activity ( V c,max) and electron transport mediated ribulose-1,5-bisphosphate (RuBP) regeneration capacity ( J max), estimated from leaf gas exchange, were significantly lower in fully expanded leaves of Anthyllis vulneraria L. (a legume) and Sanguisorba minor Scop. grown in elevated CO2. After a change in source:sink balance brought about by defoliation, photosynthetic capacity was fully restored in A. vulneraria and S. minor, but acclimation continued in the grass Bromopsis erecta (Hudson) Fourr. Changes in net photosynthesis ( P n) with growth at elevated CO2 ranged from a 1·6% reduction in precut leaves of A. vulneraria to a 47·1% stimulation in postcut leaves of S. minor . Stomatal acclimation was observed in leaves of A. vulneraria (reduced stomatal density) and B. erecta (reduced stomatal conductance). The results are discussed in terms of whole-plant resource-use optimization and chalk grassland community competitive interactions at elevated CO2.  相似文献   

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