共查询到20条相似文献,搜索用时 15 毫秒
1.
Mott KA 《Plant physiology》1988,86(1):200-203
Most studies on stomatal responses to CO2 assume that guard cells respond only to intercellular CO2 concentration and are insensitive to the CO2 concentrations in the pore and outside the leaf. If stomata are sensitive to the CO2 concentration at the surface of the leaf or in the stomatal pore, the stomatal response to intercellular CO2 concentration will be incorrect for a `normally' operating leaf (where ambient CO2 concentration is a constant). In this study asymmetric CO2 concentrations for the two surfaces of amphistomatous leaves were used to vary intercellular and leaf surface CO2 concentrations independently in Xanthium strumarium L. and Helianthus annuus L. The response of stomata to intercellular CO2 concentration when the concentration at the leaf surface was held constant was found to be the same as the response when the surface concentration was varied. In addition, stomata did not respond to changes in leaf surface CO2 concentration when the intercellular concentration for that surface was held constant. It is concluded that stomata respond to intercellular CO2 concentration and are insensitive to the CO2 concentration at the surface of the leaf and in the stomatal pore. 相似文献
2.
Elevated atmospheric CO2 alters stomatal responses to variable sunlight in a C4 grass 总被引:1,自引:1,他引:0
Native tallgrass prairie in NE Kansas was exposed to elevated (twice ambient) or ambient atmospheric CO2 levels in open-top chambers. Within chambers or in adjacent unchambered plots, the dominant C4 grass, Andropogon gerardii, was subjected to fluctuations in sunlight similar to that produced by clouds or within canopy shading (full sun > 1500 μmol m−2 s−1 versus 350 μmol m−2 s−1 shade) and responses in gas exchange were measured. These field experiments demonstrated that stomatal conductance in A. gerardii achieved new steady state levels more rapidly after abrupt changes in sunlight at elevated CO2 when compared to plants at ambient CO2. This was due primarily to the 50% reduction in stomatal conductance at elevated CO2, but was also a result of more rapid stomatal responses. Time constants describing stomatal responses were significantly reduced (29–33%) at elevated CO2. As a result, water loss was decreased by as much as 57% (6.5% due to more rapid stomatal responses). Concurrent increases in leaf xylem pressure potential during periods of sunlight variability provided additional evidence that more rapid stomatal responses at elevated CO2 enhanced plant water status. CO2-induced alterations in the kinetics of stomatal responses to variable sunlight will likely enhance direct effects of elevated CO2 on plant water relations in all ecosystems. 相似文献
3.
Increased leaf area dominates carbon flux response to elevated CO2 in stands of Populus deltoides (Bartr.) 总被引:2,自引:0,他引:2
Ramesh Murthy Greg Barron-Gafford† Phillip M. Dougherty‡ Victor C. Engel§ Katie Grieve† Linda Handley† Christie Klimas†¶ Mark J. Potosnak§ Stanley J. Zarnoch Jianwei Zhang 《Global Change Biology》2005,11(5):716-731
We examined the effects of atmospheric vapor pressure deficit (VPD) and soil moisture stress (SMS) on leaf‐ and stand‐level CO2 exchange in model 3‐year‐old coppiced cottonwood (Populus deltoides Bartr.) plantations using the large‐scale, controlled environments of the Biosphere 2 Laboratory. A short‐term experiment was imposed on top of continuing, long‐term CO2 treatments (43 and 120 Pa), at the end of the growing season. For the experiment, the plantations were exposed for 6–14 days to low and high VPD (0.6 and 2.5 kPa) at low and high volumetric soil moisture contents (25–39%). When system gross CO2 assimilation was corrected for leaf area, system net CO2 exchange (SNCE), integrated daily SNCE, and system respiration increased in response to elevated CO2. The increases were mainly as a result of the larger leaf area developed during growth at high CO2, before the short‐term experiment; the observed decline in responses to SMS and high VPD treatments was partly because of leaf area reduction. Elevated CO2 ameliorated the gas exchange consequences of water stress at the stand level, in all treatments. The initial slope of light response curves of stand photosynthesis (efficiency of light use by the stand) increased in response to elevated CO2 under all treatments. Leaf‐level net CO2 assimilation rate and apparent quantum efficiency were consistently higher, and stomatal conductance and transpiration were significantly lower, under high CO2 in all soil moisture and VPD combinations (except for conductance and transpiration in high soil moisture, low VPD). Comparisons of leaf‐ and stand‐level gross CO2 exchange indicated that the limitation of assimilation because of canopy light environment (in well‐irrigated stands; ratio of leaf : stand=3.2–3.5) switched to a predominantly individual leaf limitation (because of stomatal closure) in response to water stress (leaf : stand=0.8–1.3). These observations enabled a good prediction of whole stand assimilation from leaf‐level data under water‐stressed conditions; the predictive ability was less under well‐watered conditions. The data also demonstrated the need for a better understanding of the relationship between leaf water potential, leaf abscission, and stand LAI. 相似文献
4.
Arbutus unedo is a sclerophyllous evergreen, characteristic of Mediterranean coastal scrub vegetation. In Italy, trees of A. unedo have been found close to natural CO2 vents where the mean atmospheric carbon dioxide concentration is about 2200 μmol mol?1. Comparisons were made between trees growing in elevated and ambient CO2 concentrations to test for evidence of adaptation to long-term exposure to elevated CO2. Leaves formed at elevated CO2 have a lower stomatal density and stomatal index and higher specific leaf area than those formed at ambient CO2, but there was no change in carbon to nitrogen ratios of the leaf tissue. Stomatal conductance was lower at elevated CO2 during rapid growth in the spring. In mid-summer, under drought stress, stomatal closure of all leaves occurred and in the autumn, when stress was relieved, the conductance of leaves at both elevated and ambient CO2 increased. In the spring, the stomatal conductance of the new flush of leaves at ambient CO2 was higher than the leaves at elevated CO2, increasing instantaneous water use efficiency at elevated CO2. Chlorophyll fluorescence measurements suggested that elevated CO2 provided some protection against photoinhibition in mid-summer. Analysis of A/Ci curves showed that there was no evidence of either upward or downward regulation of photosynthesis at elevated CO2. It is therefore anticipated that A. unedo will have higher growth rates as the ambient CO2 concentrations increase. 相似文献
5.
Laura Serna 《Plant signaling & behavior》2008,3(4):214-217
Gas exchange between the plant and the atmosphere is regulated by controlling both the stomatal density and the aperture of the stomatal pore. Environmental factors such as light, the level of atmospheric CO2 and hormones regulate stomatal development and/or function. Because atmospheric CO2 levels have been rising since the Industrial Revolution, and it is predicted that they will continue doing so in the future, an understanding of the CO2 signalling mechanisms in the stomatal responses will help to know how plants were in the past and will allow predicting how they will respond to climate change in the near future. This article covers the recent knowledge of the CO2 signalling mechanisms that regulate both stomatal function and development.Key words: Arabidopsis, CO2, development, epidermis, gas exchange, leaf, patterning, stoma 相似文献
6.
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
7.
D.J. Beerling 《Acta Oecologica》1997,18(6):697
The Climate Change Experiment (CLIMEX) is a unique large scale facility in which an entire undisturbed catchment of boreal vegetation has been exposed to elevated CO2 (560 ppm) and temperature (+3°C summer, +5°C winter) for the past three years with all the soil-plant-atmosphere linkages intact. Here, carbon isotope composition and stomatal density have been analysed from sequential year classes of needles of mature Scots pine trees (Pinus sylvestris L.) to investigate the response of time-integrated water-use efficiency (UWE) and stomatal density to CO2 enrichment and climate change. Carbon isotope discrimination decreased and WUE increased in cohorts of needles developing under increased CO2 and temperature, compared to needles on the same trees developing in pretreatment years. Mid-season instantaneous gas exchange, measured on the same trees for the past four years, indicated that these responses resulted from higher needle photosynthetic rates and reduced stomatal conductance. Needles of P. sylvestris developing under increased CO2 and temperature had consistently lower stomatal densities than their ambient grown counterparts on the same trees. The stomatal density of P. sylvestris needles was inversely correlated with δ13C-derived WUE, implying some effect of this morphological response on leaf gas exchange. Future atmospheric CO2 and temperature increases are therefore likely to improve the water economy of P. sylvestris, at least at the scale of individual needles, by affecting stomatal density and gas exchange processes. 相似文献
8.
Stomatal regulation in a changing climate: a field study using Free Air Temperature Increase (FATI) and Free Air CO2 Enrichment (FACE) 总被引:2,自引:2,他引:0
This study investigates effects of climate warming (+ 2.5°C ubove ambient) and elevated CO2 concentration (600 μmol mol?1) on the stomatal functioning and the water relations of Lolium perenne, using Free Air Temperature Increase (FATI) and Free Air CO2 Enrichment (FACE). Compared to growth at ambient temperature, whole-season temperature increase reduced leaf stomatal conductance, but only at the top of the canopy (-14.6 and -8.8% at ambient and elevated CO2, respectively). However, because higher canopy temperature raised the leaf-to-air vapour pressure difference, leaf transpiration rate increased (+28% at ambient and +48% at elevated CO2) and instantaneous leaf water use efficiency, derived from short-term measurements of assimilation and transpiration rate, declined (-11% at ambient and -13% at elevated CO2). Nevertheless, at the stand level, growth at + 2.5°C reduced transpiration due to fewer tillers per plant and a smaller leaf area per tiller. This sparser vegetation was also more closely coupled to the atmosphere and maintained a drier internal microclimate. To assess whether the stomatal behaviour observed in this experiment could be explained by prevailing concepts of stomatal functioning, three models were applied (Cowan 1977; Ball, Woodrow & Berry 1987; Leuning 1995). The latter model accounted for the highest proportion of variability in the data (58%) and was insensitive to CO2 and temperature regime, which suggests that the principles of stomatal regulation are not affected by changes in CO2 or climate. 相似文献
9.
Contrasting responses of leaf stomatal characteristics to climate change: a considerable challenge to predict carbon and water cycles
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Zhouping Shangguan 《Global Change Biology》2017,23(9):3781-3793
Stomata control the cycling of water and carbon between plants and the atmosphere; however, no consistent conclusions have been drawn regarding the response of stomatal frequency to climate change. Here, we conducted a meta‐analysis of 1854 globally obtained data series to determine the response of stomatal frequency to climate change, which including four plant life forms (over 900 species), at altitudes ranging from 0 to 4500 m and over a time span of more than one hundred thousand years. Stomatal frequency decreased with increasing CO2 concentration and increased with elevated temperature and drought stress; it was also dependent on the species and experimental conditions. The response of stomatal frequency to climate change showed a trade‐off between stomatal control strategies and environmental factors, such as the CO2 concentration, temperature, and soil water availability. Moreover, threshold effects of elevated CO2 and temperature on stomatal frequency were detected, indicating that the response of stomatal density to increasing CO2 concentration will decrease over the next few years. The results also suggested that the stomatal index may be more reliable than stomatal density for determination of the historic CO2 concentration. Our findings indicate that the contrasting responses of stomata to climate change bring a considerable challenge in predicting future water and carbon cycles. 相似文献
10.
The response of adaxial and abaxial stomatal conductance in Rumex obtusifolius to growth at elevated atmospheric concentrations of CO2 (250 μmol mol?1 above ambient) was investigated over two growing seasons. The conductance of both the adaxial and abaxial leaf surfaces was found to be reduced by elevated concentrations of CO2. Elevated CO2 caused a much greater reduction in conductance for the adaxial surface than for the abaxial surface. The absence of effects upon stomatal density indicated that the reductions were probably the result of changes in stomatal aperture. Partitioning of gas exchange between the leaf surfaces revealed that increased concentrations of CO2 caused increased rates of photosynthesis only via the abaxial surface. Additionally, leaf thickness was found to increase during growth at elevated concentrations of CO2. The tendency for these amphistomatous leaves to develop a distribution of conductance approaching that of hypostomatous leaves clearly reduced their maximum photosynthetic potential. This conclusion was supported by measurements of stomatal limitation, which showed greater values for the adaxial surfaces, and greater values at elevated CO2. This reduction in photosynthesis may in part be caused by higher diffusive limitations imposed because of increased leaf thickness. In an uncoupled canopy, asymmetrical stomatal responses of the kind identified here may appreciably reduce transpiration. Species which show symmetrical responses are less likely to show reduced transpirational rates, and a redistribution of water loss between species may occur. The implications of asymmetrical stomatal responses for photosynthesis and canopy transpiration are discussed. 相似文献
11.
Stomatal sensitivity to vapour pressure difference over a subambient to elevated CO2 gradient in a C3 /C4 grassland 总被引:1,自引:0,他引:1
In the present study the response of stomatal conductance (gs) to increasing leaf‐to‐air vapour pressure difference (D) in early season C3 (Bromus japonicus) and late season C4 (Bothriochloa ischaemum) grasses grown in the field across a range of CO2 (200–550 µmol mol?1) was examined. Stomatal sensitivity to D was calculated as the slope of the response of gs to the natural log of externally manipulated D (dgs/dlnD). Increasing D and CO2 significantly reduced gs in both species. Increasing CO2 caused a significant decrease in stomatal sensitivity to D in Br. japonicus, but not in Bo. ischaemum. The decrease in stomatal sensitivity to D at high CO2 for Br. japonicus fit theoretical expectations of a hydraulic model of stomatal regulation, in which gs varies to maintain constant transpiration and leaf water potential. The weaker stomatal sensitivity to D in Bo. ischaemum suggested that stomatal regulation of leaf water potential was poor in this species, or that non‐hydraulic signals influenced guard cell behaviour. Photosynthesis (A) declined with increasing D in both species, but analyses of the ratio of intercellular to atmospheric CO2 (Ci/Ca) suggested that stomatal limitation of A occurred only in Br. japonicus. Rising CO2 had the greatest effect on gs and A in Br. japonicus at low D. In contrast, the strength of stomatal and photosynthetic responses to CO2 were not affected by D in Bo. ischaemum. Carbon and water dynamics in this grassland are dominated by a seasonal transition from C3 to C4 photosynthesis. Interspecific variation in the response of gs to D therefore has implications for predicting seasonal ecosystem responses to CO2. 相似文献
12.
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
13.
Gerhard E. Overbeck Sandra C. Müller Valério D. Pillar Jörg Pfadenhauer 《Plant Ecology》2006,184(2):237-243
The inverse relationship between numbers of stomata (stomatal frequency) on tree leaves and ambient CO2 concentration is increasingly applied for reconstructing past atmospheric CO2 levels. The abundance of leaf remains of Quercus robur in Holocene peat and lake deposits in Europe makes this species potentially suitable for high-resolution stomatal frequency
analysis. In order to quantify the CO2 responsiveness of the species, the behavior of the stomatal index for Q. robur during the current anthropogenic CO2 increase is determined on the basis of buried, herbarium and modern leaf material from the Netherlands. The stomatal index
(SI), expressing the ratio of the number of stomata in a given area divided by the total number of stomata and other epidermal
cells in that same area, is used in order to minimize influences on stomatal frequency of environmental conditions other than
CO2. The sigmoid SI response pattern recorded for Q. robur resembles that of the closely related species Q. petraea, although there is a difference in the timing of the response limitation of the two species to increasing atmospheric CO2. For calibration purposes only the linear phase of the sigmoidal response curve is taken into consideration in the presented
CO2 response model, which allows confident combination of Q. robur and Q. petraea over the interval from 290 to 325 ppmv CO2. The model is conservative in reconstructing past CO2 mixing ratios outside the range of monitored response. As a result of the observed SI response limit, the model predicts
CO2 levels below 325 ppmv with a mean error of 10.2 ppmv, whereas higher CO2 levels are underestimated. 相似文献
14.
Jasmonate‐mediated stomatal closure under elevated CO2 revealed by time‐resolved metabolomics
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Sisi Geng Biswapriya B. Misra Evaldo de Armas David V. Huhman Hans T. Alborn Lloyd W. Sumner Sixue Chen 《The Plant journal : for cell and molecular biology》2016,88(6):947-962
Foliar stomatal movements are critical for regulating plant water loss and gas exchange. Elevated carbon dioxide (CO2) levels are known to induce stomatal closure. However, the current knowledge on CO2 signal transduction in stomatal guard cells is limited. Here we report metabolomic responses of Brassica napus guard cells to elevated CO2 using three hyphenated metabolomics platforms: gas chromatography‐mass spectrometry (MS); liquid chromatography (LC)‐multiple reaction monitoring‐MS; and ultra‐high‐performance LC‐quadrupole time‐of‐flight‐MS. A total of 358 metabolites from guard cells were quantified in a time‐course response to elevated CO2 level. Most metabolites increased under elevated CO2, showing the most significant differences at 10 min. In addition, reactive oxygen species production increased and stomatal aperture decreased with time. Major alterations in flavonoid, organic acid, sugar, fatty acid, phenylpropanoid and amino acid metabolic pathways indicated changes in both primary and specialized metabolic pathways in guard cells. Most interestingly, the jasmonic acid (JA) biosynthesis pathway was significantly altered in the course of elevated CO2 treatment. Together with results obtained from JA biosynthesis and signaling mutants as well as CO2 signaling mutants, we discovered that CO2‐induced stomatal closure is mediated by JA signaling. 相似文献
15.
A. Noormets A. Sôber E. J. Pell R. E. Dickson G. K. Podila J. Sôber J. G. Isebrands & D. F. Karnosky 《Plant, cell & environment》2001,24(3):327-336
Leaf gas exchange parameters and the content of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) in the leaves of two 2‐year‐old aspen (Populus tremuloides Michx.) clones (no. 216, ozone tolerant and no. 259, ozone sensitive) were determined to estimate the relative stomatal and mesophyll limitations to photosynthesis and to determine how these limitations were altered by exposure to elevated CO2 and/or O3. The plants were exposed either to ambient air (control), elevated CO2 (560 p.p.m.) elevated O3 (55 p.p.b.) or a mixture of elevated CO2 and O3 in a free air CO2 enrichment (FACE) facility located near Rhinelander, Wisconsin, USA. Light‐saturated photosynthesis and stomatal conductance were measured in all leaves of the current terminal and of two lateral branches (one from the upper and one from the lower canopy) to detect possible age‐related variation in relative stomatal limitation (leaf age is described as a function of leaf plastochron index). Photosynthesis was increased by elevated CO2 and decreased by O3 at both control and elevated CO2. The relative stomatal limitation to photosynthesis (ls) was in both clones about 10% under control and elevated O3. Exposure to elevated CO2 + O3 in both clones and to elevated CO2 in clone 259, decreased ls even further – to about 5%. The corresponding changes in Rubisco content and the stability of Ci/Ca ratio suggest that the changes in photosynthesis in response to elevated CO2 and O3 were primarily triggered by altered mesophyll processes in the two aspen clones of contrasting O3 tolerance. The changes in stomatal conductance seem to be a secondary response, maintaining stable Ci under the given treatment, that indicates close coupling between stomatal and mesophyll processes. 相似文献
16.
Saturation Kinetics of the Velocity of Stomatal Closing in Response to CO(2) 总被引:3,自引:3,他引:0
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Raschke K 《Plant physiology》1972,49(2):229-234
Stomatal closing movements in response to changes from CO2-free to CO2-containing air were recorded in leaf sections of Zea mays using air flow porometers. The response to CO2 was fast; the shortest lag between the application of 300 microliters CO2 per liter of air and the beginning of a stomatal response was 3 seconds. The velocity of stomatal closing increased with CO2 concentration and approached its maximal value between 103 and 104 microliters CO2 per liter of air. The CO2 concentration at which the closing velocity reached half its maximal value was approximately 200 microliters CO2 per liter of air, both in the light and in darkness. This indicates that the mechanism of stomatal responses to CO2 is the same in both light regimes and that the range of stomatal sensitivity to changes in CO2 concentration coincides with the range of CO2 concentrations known to occur in the intercellular spaces of illuminated leaves. 相似文献
17.
Summary At constant cladode temperature the stomatal resistance of O. inermis increased when the cladode-air vapor pressure difference was increased and stomatal resistance decreased when the cladode-air vapor pressure difference was lowered. Net CO2 fixation in the dark was very responsive to these humidity dependent changes in stomatal resistance. Net CO2 fixation and stomatal resistance in the light did not respond to changes in cladode-air vapor pressure differences in the light under the conditions tested. When temperature response functions for dark CO2 fixation were examined at constant ambient humidity, the reduction in dark CO2 fixation at higher temperatures was largely due to stomatal closure in response to the increased vapor pressure difference. The water requirement for net CO2 fixation in the dark at typical nocturnal vapor pressure differences was about 10 times lower than that of net CO2 fixation in the light at vapor pressure differences typical of the late afternoon. The role of the stomatal responses to humidity in determining the patterns and rates of net CO2 exchange in the light or dark, and its possible ecological significance is discussed. 相似文献
18.
19.
Physiological Site of Ethylene Effects on Carbon Dioxide Assimilation in Glycine max L. Merr 总被引:1,自引:0,他引:1
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The physiological site of ethylene action on CO2 assimilation was investigated in intact plants of Glycine max L., using a whole-plant, open exposure system equipped witha remotely operated single-leaf cuvette. The objective of the study was met by investigating in control and ethylene-treated plants the (a) synchrony in response of CO2 assimilation, stomatal conductance to water vapor, and substomatal CO2 partial pressure; (b) response of CO2 assimilation as a function of a range of substomatal CO2 partial pressures; and (c) response of CO2 assimilation as a function of a range of photon flux densities. After exposure to 410 micromoles per cubic meter of ethylene for 2.0 hours, CO2 assimilation and stomatal conductance declined in synchrony, while substomatal CO2 partial pressure remained unchanged until exposure times equaled and exceeded 3.0 hours. Because incipient changes in CO2 assimilation occurred without a change in the CO2 partial pressure in the leaf interior, it is concluded that both stomatal physiology and the chloroplast's CO2 assimilatory capacity were initial sites of ethylene action. After 3.5 hours the effect of ethylene on stomatal conductance and CO2 assimilation exhibited saturation kinetics, and the effect was substantially more pronounced for stomatal conductance than for CO2 assimilation. Based on the response of CO2 assimilation to a range of substomatal CO2 partial pressures, ethylene did not affect either the CO2 compensation point or carboxylation efficiency at subsaturating CO2 partial pressures. Above-ambient supplies of CO2 did not alleviate the diminished rates of CO2 assimilation. In partitioning the limitations imposed on CO2 assimilation in control and ethylene-treated plants, the stomatal component accounted for only 16 and 4%, respectively. The response of CO2 assimilation to a range of photon flux densities suggests that ethylene reduced apparent quantum yield by nearly 50%. Thus, the pronounced decline in net photosynthetic CO2 assimilation in the presence of ethylene was due more to a loss in the mesophyll tissue's intrinsic capacity to assimilate CO2 than to a reduction in stomatal conductance. 相似文献
20.
Heterogenous stomatal closure in response to leaf water deficits is not a universal phenomenon 总被引:5,自引:2,他引:3
The extent and occurrence of water stress-induced “patchy” CO2 uptake across the surface of leaves was evaluated in a number of plant species. Leaves, while still attached to a plant, were illuminated and exposed to air containing [14C]CO2 before autoradiographs were developed. Plant water deficits that caused leaf water potential depression to −1.1 megapascals during a 4-day period did result in heterogenous CO2 assimilation patterns in bean (Phaseolus vulgaris). However, when the same level of stress was imposed more gradually (during 17 days), no patchy stomatal closure was evident. The patchy CO2 assimilation pattern that occurs when bean plants are subjected to a rapidly imposed stress could induce artifacts in gas exchange studies such that an effect of stress on chloroplast metabolism is incorrectly deduced. This problem was characterized by examining the relationship between photosynthesis and internal [CO2] in stressed bean leaves. When extent of heterogenous CO2 uptake was estimated and accounted for, there appeared to be little difference in this relationship between control and stressed leaves. Subjecting spinach (Spinacea oleracea) plants to stress (leaf water potential depression to −1.5 megapascals) did not appear to cause patchy stomatal closure. Wheat (Triticum aestivum) plants also showed homogenous CO2 assimilation patterns when stressed to a leaf water potential of −2.6 megapascals. It was concluded that water stress-induced patchy stomatal closure can occur to an extent that could influence the analysis of gas exchange studies. However, this phenomenon was not found to be a general response. Not all stress regimens will induce patchiness; nor will all plant species demonstrate this response to water deficits. 相似文献