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1.
JEAN-CHRISTOPHE DOMEC SARI PALMROTH ERIC WARD CHRIS A. MAIER M. THÉRÉZIEN & RAM OREN 《Plant, cell & environment》2009,32(11):1500-1512
We investigated how leaf hydraulic conductance (Kleaf) of loblolly pine trees is influenced by soil nitrogen amendment (N) in stands subjected to ambient or elevated CO2 concentrations (CO2a and CO2e, respectively). We also examined how Kleaf varies with changes in reference leaf water potential (Ψleaf‐ref) and stomatal conductance (gs‐ref) calculated at vapour pressure deficit, D of 1 kPa. We detected significant reductions in Kleaf caused by N and CO2e, but neither treatment affected pre‐dawn or midday Ψleaf. We also detected a significant CO2e‐induced reduction in gs‐ref and Ψleaf‐ref. Among treatments, the sensitivity of Kleaf to Ψleaf was directly related to a reference Kleaf (Kleaf‐ref computed at Ψleaf‐ref). This liquid‐phase response was reflected in a similar gas‐phase response, with gs sensitivity to D proportional to gs‐ref. Because leaves represented a substantial component of the whole‐tree conductance, reduction in Kleaf under CO2e affected whole‐tree water use by inducing a decline in gs‐ref. The consequences of the acclimation of leaves to the treatments were: (1) trees growing under CO2e controlled morning leaf water status less than CO2a trees resulting in a higher diurnal loss of Kleaf; (2) the effect of CO2e on gs‐ref was manifested only during times of high soil moisture. 相似文献
2.
Elevated CO2 mitigates chilling-induced water stress and photosynthetic reduction during chilling 总被引:1,自引:1,他引:0
Bean, cucumber and corn plants were grown in controlled-environment chambers at 25/18 °C day/night temperature and either ambient (350 μmol mol?1) or elevated (700 μmol mol?1) CO2 concentration, and at 20–30 d after emergence they were exposed to a 24 h chilling treatment (6.5 ± 1.5 °C) at their growth CO2 concentration. Whole-plant transpiration rates (per unit leaf area basis) during the first 3 h of chilling were about 26,28 and 13% lower at elevated than at ambient CO2 for bean, cucumber and corn, respectively. The decline in leaf water potential (ψL) and visible wilting of bean and cucumber during chilling were significantly less at elevated than at ambient CO2. Corn ψL was not significantly affected by chilling, and corn did not exhibit any other symptoms of chilling-induced water stress. Leaf osmotic potentials (measured before chilling only) of bean and cucumber were more negative at elevated than at ambient CO2, and the corresponding calculated leaf turgor potentials were significantly higher at elevated than at ambient CO2. Leaf relative water content (RWC) during chilling at ambient CO2fell to 62 and 48% for bean and cucumber, respectively. RWC during chilling at elevated CO2 was never below 79% for bean or 63% for cucumber. Corn RWC was not measured. After 24 h of chilling at ambient CO2, net photosynthetic rate (PN) reductions were 83, 89 and 24% for bean, cucumber and corn, respectively. PN reductions during chilling were less at elevated CO2: 53, 40 and 4% for bean, cucumber and corn, respectively. At ambient CO2, none of the species fully recovered to pre-chilling PN, but at elevated CO2 both bean and corn recovered fully. The average percentage leaf area with visible leaf damage due to chilling was 20.6 and 9.6% at ambient and elevated CO2, respectively, for bean, and 32.4 and 23.6% at ambient and elevated CO2, respectively, for cucumber. Corn showed no significant permanent leaf damage from chilling at either CO2 concentration. These results indicate that cucumber was most sensitive to chilling as imposed in this study, followed by bean and corn. The results support the hypothesis that, at least in young plants under controlled-environment conditions, elevated CO2 improves plant water relations during chilling and can mitigate photosynthetic depression and chilling damage. The implications for long-term growth and reproductive success in managed and natural ecosystems will require testing of this hypothesis under field conditions. 相似文献
3.
Three levels of atmospheric CO2 and 2 levels of relative humidity (RH) during the rooting period were tested for their effect on several factors presumed to influence adventitious root formation in leafy pea ( Pisum sativum L. cv. Alaska) cuttings. Compared to normal CO2 levels (350 μl l−1 ), neither 1800 nor 675 μl l−1 CO2 affected the rooting percentage or the number of roots per cutting. However, 1800 μl l−1 CO2 increased root and shoot dry weight, root length, carbohydrate levels in the base of the cuttings and water potential (Ψw ) of cuttings compared to normal levels of CO2 . Compared to 87% RH. 55% RH decreased all of the above parameters, including the number of roots per cutting. A polyvinyl chloride antitranspirant (which partially blocks stomata and slows photosynthesis) applied simultaneously with 87% RH increased Ψw and root length but lowered all of the other above parameters, compared to 87% RH without antitranspirant. Increasing current photosynthate (products of photosynthetic activity after excision), carbohydrate, or Ψw either alone or together was associated with increased root system size but not necessarily with increased rooting percentage or root number. The data are consistent with a hypothesis that the number of roots per cutting increased with increasing current photosynthate and carbohydrate until some other factor became limiting. Also, the effect of Ψw on rooting percentage and root number was mediated through its effect on current photosynthate and carbohydrate. 相似文献
4.
1. One-year-old seedlings of shade tolerant Acer rubrum and intolerant Betula papyrifera were grown in ambient and twice ambient (elevated) CO2 , and in full sun and 80% shade for 90 days. The shaded seedlings received 30-min sun patches twice during the course of the day. Gas exchange and tissue–water relations were measured at midday in the sun plants and following 20 min of exposure to full sun in the shade plants to determine the effect of elevated CO2 on constraints to sun-patch utilization in these species.
2. Elevated CO2 had the largest stimulation of photosynthesis in B. papyrifera sun plants and A. rubrum shade plants.
3. Higher photosynthesis per unit leaf area in sun plants than in shade plants of B. papyrifera was largely owing to differences in leaf morphology. Acer rubrum exhibited sun/shade differences in photosynthesis per unit leaf mass consistent with biochemical acclimation to shade.
4. Betula papyrifera exhibited CO2 responses that would facilitate tolerance to leaf water deficits in large sun patches, including osmotic adjustment and higher transpiration and stomatal conductance at a given leaf-water potential, whereas A. rubrum exhibited large increases in photosynthetic nitrogen-use efficiency.
5. Results suggest that species of contrasting successional ranks respond differently to elevated CO2 , in ways that are consistent with the habitats in which they typically occur. 相似文献
2. Elevated CO
3. Higher photosynthesis per unit leaf area in sun plants than in shade plants of B. papyrifera was largely owing to differences in leaf morphology. Acer rubrum exhibited sun/shade differences in photosynthesis per unit leaf mass consistent with biochemical acclimation to shade.
4. Betula papyrifera exhibited CO
5. Results suggest that species of contrasting successional ranks respond differently to elevated CO
5.
The effect of NaCl salinity at concentrations of 43–173 mM in nutrient solution on net gas exchange of attached cowpea [Vigna unguiculata (L.) Walp cv. California Black-eye No. 5 (CB5)] leaves was investigated under both greenhouse and growth chamber conditions.
There was a marked decrease in leaf conductance to water vapor after exposure to low salinity levels and a slighter decrease when salinity levels were higher. The decrease in net assimilation was much more gradual throughout the entire salinity range. The altered responses of net assimilation and leaf conductance to salinity were more evident at a high light intensity. A decrease in intercellular partial CO2 pressure [p(CO2 )] was found at the low and intermediate salinity levels but not at the high level. These findings suggest that CO, assimilation was mainly controlled by stomatal conductance and the fixation of CO, might have been increased due to stimulated biochemical activity or to higher chlorophyll concentration per unit leaf area. A decrease in assimilation was already found one day after salinization and pro-ceeded up to 4 days when it was inhibited by 50% at 43 mM NaCl and up to 85% at 173 mM. The decrease in transpiration was larger than the decrease in net assimila-tion, and both were attributed to osmotic stress. Partial recovery was found thereaf-ter and new steady-state rates, in the range of 55 to 100% of the control, were then obtained for salinity levels between 43 and 130 mM. Inhibition of net CO, assimila-tion at this stage was attributed partly to a specific sodium effect and partly to plant water status. A linear relationship between leaf sodium content and net photosynthe-sis was also evident at this stage. Net CO, assimilation recovered more completely than transpiration when salt stress was removed, but at 173 mM NaCl recovery was neglible. 相似文献
There was a marked decrease in leaf conductance to water vapor after exposure to low salinity levels and a slighter decrease when salinity levels were higher. The decrease in net assimilation was much more gradual throughout the entire salinity range. The altered responses of net assimilation and leaf conductance to salinity were more evident at a high light intensity. A decrease in intercellular partial CO
6.
For cacti with persistent, relatively large leaves, most shoot CO2 uptake under well-watered conditions occurs by the leaves using the C3 pathway. For three species in the primitive subfamily Pereskioideae, droughts of 7 or 14 days decreased leaf daytime net CO2 uptake by an average of 49 and 88%, respectively; these species always had a net CO2 release at night by the leaves and both at night and during the day by the stems. For three leafy species in subfamily Opuntioideae, 7 and 14 days of drought reduced leaf daytime net CO2 uptake by 90 and 100%, respectively. Although drought reduced the total CO2 uptake over 24 h, the average percentage occurring at night by the leaves of these species increased from 5% under wet conditions to 71% after 7 days of drought to 99% after 14 days of drought. For two of the three species of Opuntioideae, 7 days of drought caused the small net CO2 uptake by the sterns to shift from the daytime to the nighttime, while for the third species drought caused a reduction of its stem nocturnal net CO2 uptake. Thus, shifts from predominantly daytime to predominantly nighttime net CO2 uptake can be induced by drought for the leaves and the stems of leafy cacti in subfamily Opuntioideae, indicating a high degree of biochemical versatility. 相似文献
7.
Assessing elevated CO2 responses using meta-analysis 总被引:1,自引:1,他引:0
8.
Root-derived CO2 efflux via xylem stream rivals soil CO2 efflux 总被引:2,自引:2,他引:0
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10.
高粱抗旱品种3197B比不抗旱品种三尺三在水分胁迫条件下ψ_S下降低。在相同ψ_S时,3197B相对含水量高于三尺三。水分胁迫期间,3197B能始终维持比三尺三较高的ψ_P。在中度和严重水分胁迫时,3197B几种渗透物质积累均高于三尺三,其中可溶性糖和K~ 对渗透调节贡献最大。水分胁迫下,3197B正展开叶渗透调节能力较强,ψ_P维持较高,临界膨压低,叶片扩张性能小、故生长速率随ψ_W下降较慢。 相似文献
11.
Anne Kasurinen Paula Kokko-Gonzales Johanna Riikonen † Elina Vapaavuori† Toini Holopainen 《Global Change Biology》2004,10(10):1654-1665
In the present open‐top chamber experiment, two silver birch clones (Betula pendula Roth, clone 4 and clone 80) were exposed to elevated levels of carbon dioxide (CO2) and ozone (O3), singly and in combination, and soil CO2 efflux was measured 14 times during three consecutive growing seasons (1999–2001). In the beginning of the experiment, all experimental trees were 7 years old and during the experiment the trees were growing in sandy field soil and fertilized regularly. In general, elevated O3 caused soil CO2 efflux stimulation during most measurement days and this stimulation enhanced towards the end of the experiment. The overall soil respiration response to CO2 was dependent on the genotype, as the soil CO2 efflux below clone 80 trees was enhanced and below clone 4 trees was decreased under elevated CO2 treatments. Like the O3 impact, this clonal difference in soil respiration response to CO2 increased as the experiment progressed. Although the O3 impact did not differ significantly between clones, a significant time × clone × CO2× O3 interaction revealed that the O3‐induced stimulation of soil respiration was counteracted by elevated CO2 in clone 4 on most measurement days, whereas in clone 80, the effect of elevated CO2 and O3 in combination was almost constantly additive during the 3‐year experiment. Altogether, the root or above‐ground biomass results were only partly parallel with the observed soil CO2 efflux responses. In conclusion, our data show that O3 impacts may appear first in the below‐ground processes and that relatively long‐term O3 exposure had a cumulative effect on soil CO2 efflux. Although the soil respiration response to elevated CO2 depended on the tree genotype as a result of which the O3 stress response might vary considerably within a single tree species under elevated CO2, the present experiment nonetheless indicates that O3 stress is a significant factor affecting the carbon cycling in northern forest ecosystems. 相似文献
12.
R. S. SENOCK J. M. HAM T. M. LOUGHIN B. A. KIMBALL D. J. HUNSAKER P. J. PINTER G. W. WALL R. L. GARCIA R. L. LaMORTE 《Plant, cell & environment》1996,19(2):147-158
The effects of elevated carbon dioxide (CO2) concentration on plant water use are best evaluated on plants grown under field conditions and with measurement techniques that do not disturb the natural function of the plant. Heat balance sap flow gauges were used on individual main stems of wheat (Triticum aestivum L. cv Yecora rojo) grown under normal ambient conditions (control) and in a free-air CO2 enrichment (FACE) system in Arizona with either high (control + high H2O = CW; FACE + high H2O = FW) or low (control + low H2O = CD; FACE + low H2O = FD) irrigation regimens. Over a 30d period (stem elongation to anthesis), combinations of treatments were monitored with,10–40 gauges per treatment. The effects of increased CO2 on tiller water use were inconsistent in both the diurnal patterns of sap flow and the statistical analyses of daily sap flow (Ftot). Initial results suggested that the reductions in Ftot, from CO2 enrichment were small (,0–10%) in relation to the H2O treatment effect (,20–30%). For a 3d period, Ftot of FW was,19–26% less than that of CW (P = 0.10). Examination of the different sources of variation in the study revealed that the location of gauges within the experimental plots influenced the variance of the sap flow measurements. This variation was probably related to positional variation in subsurface drip lines used to irrigate plots. A sampling design was proposed for use of sap flow gauges in FACE systems with subsurface irrigation that takes into account the main treatment effects of CO2 enrichment and the other sources of variation identified in this study. Despite the small and often statistically non-significant differences in Ftot between the CW and FW treatments, cumulative water use of the FW treatment at the end of the first three test periods ranged from 7 to 23% lower than that of the CW treatment. Differences in sap flow between FW and CW compared well with treatment differences in evapotranspiration. The results of the study, based on the first reported sap flow measurements of wheat, suggest that irrigation requirements for wheat production, in the present climatic regimen of the south-western US, may be predicted to decrease slightly because of increasing atmospheric CO2. 相似文献
13.
Short-term exposure to high CO2 increases rates of photosynthesis and growth in soybeans, but with prolonged high CO2 exposure, these high rates are sometimes not maintained. Growth of soybean (Glycine max (L.) Merrill cv. Fiskeby V) seedlings kept for 25 days at atmospheres of 350 or 1000 μ/l CO2 was compared with growth of plants given 2, 4 or 6 day alternating exposure to high and low CO2 levels (13 days of total exposure to each level). Final dry weight of plants increased with number of days in high CO2 but leaf areas were not greatly affected. Thus dry weight gains per unit leaf area (net assimilation rates) were higher in high CO2 than in low CO2 throughout the entire period of the experiment and the pattern of exposure to high CO2 did not affect the rate of dry weight gain in high CO2 . 相似文献
14.
Abstract. Germination modes of lower seeds of cocklebur (Xanthium pennsylvanicum Wallr.) under different water stresses, prepared with mannitol solution, were examined in relation to gaseous factors. As the concentration of mannitol increased, germination was increasingly inhibited at a mode which was drawn by two straight lines having different slopes and meeting at an angle. One is a sharp line occurring at the lower concentrations of mannitol; the other is a gentle line occurring at higher concentrations of mannitol. The former reflected the growth response of axial tissues to mild water stress, whereas the latter reflected the growth response of cotyledonary tissues to severe water stress. The germination potential of cocklebur seeds increased with increasing temperature. Thus, the seeds were more resistant to water stress at higher than al lower temperatures. This increased germination potential under water stress resulted from the greater growth potential of axial tissues, but not cotyledonary tissues, at higher temperature. Increased O2 levels improved both the reduced axial and cotyledonary growth under water stress. Carbon dioxide predominantly enhanced axial growth under water stress, whereas C2H4 exclusively enhanced cotyledonary growth. Thus, these gases were effective in potentiating germination under water stress. When combined with each other, these gases caused more pronounced growth of the axial and cotyledonary tissues, leading to germination under more severe water stresses. Maximal axial and cotyledonary growth under water stress occurred in the simultaneous presence of CO2, C2H4 and O2, which allowed the germination at higher mannitol concentrations above 0.6 kmol m?3 From these results, it was suggested that cocklebur seeds would override water stress by depending upon both the Corresponding axial growth and the C2H4-responding cotyledonary growth. 相似文献
15.
Abstract. Very little attention has been directed at the responses of tropical plants to increases in global atmospheric CO2 concentrations and the potential climatic changes. The available data, from greenhouse and laboratory studies, indicate that the photosynthesis, growth and water use efficiency of tropical plants can increase at higher CO2 concentrations. However, under field conditions abiotic (light, water or nutrients) or biotic (competition or herbivory) factors might limit these responses. In general, elevated atmospheric CO2 concentrations seem to increase plant tolerance to stress, including low water availability, high or low temperature, and photoinhibition. Thus, some species may be able to extend their ranges into physically less favourable sites, and biological interactions may become relatively more important in determining the distribution and abundance of species. Tropical plants may be more narrowly adapted to prevailing temperature regimes than are temperate plants, so expected changes in temperature might be relatively more important in the tropics. Reduced transpiration due to decreased stomatal conductance could modify the effects of water stress as a cue for vegetative or reproductive phenology of plants of seasonal tropical areas. The available information suggests that changes in atmospheric CO2 concentrations could affect processes as varied as plant/herbivore interactions, decomposition and nutrient cycling, local and geographic distributions of species and community types, and ecosystem productivity. However, data on tropical plants are few, and there seem to be no published tropical studies carried out in the field. Immediate steps should be undertaken to reduce our ignorance of this critical area. 相似文献
16.
The nature of the interaction between drought and elevated CO2 partial pressure (pCa) is critically important for the effects of global change on crops. Some crop models assume that the relative responses of transpiration and photosynthesis to soil water deficit are unaltered by elevated pCa, while others predict decreased sensitivity to drought at elevated pCa. These assumptions were tested by measuring canopy photosynthesis and transpiration in spring wheat (cv. Minaret) stands grown in boxes with 100 L rooting volume. Plants were grown under controlled environments with constant light (300 µmol m?2 s?1) at ambient (36 Pa) or elevated (68 Pa) pCa and were well watered throughout growth or had a controlled decline in soil water starting at ear emergence. Drought decreased final aboveground biomass (?15%) and grain yield (?19%) while elevated pCa increased biomass (+24%) and grain yield (+29%) and there was no significant interaction. Elevated pCa increased canopy photosynthesis by 15% on average for both water regimes and increased dark respiration per unit ground area in well‐watered plants, but not drought‐grown ones. Canopy transpiration and photosynthesis were decreased in drought‐grown plants relative to well‐watered plants after about 20–25 days from the start of the drought. Elevated pCa decreased transpiration only slightly during drought, but canopy photosynthesis continued to be stimulated so that net growth per unit water transpired increased by 21%. The effect of drought on canopy photosynthesis was not the consequence of a loss of photosynthetic capacity initially, as photosynthesis continued to be stimulated proportionately by a fixed increase in irradiance. Drought began to decrease canopy transpiration below a relative plant‐available soil water content of 0.6 and canopy photosynthesis and growth below 0.4. The shape of these responses were unaffected by pCa, supporting the simple assumption used in some models that they are independent of pCa. 相似文献
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18.
CO2 and intracellular pH 总被引:2,自引:2,他引:0
ALAN W. BOWN 《Plant, cell & environment》1985,8(6):459-465
Abstract The experimental determination of cytoplasmic and vacuolar pH values is discussed. Despite variation in these values evidence indicates that intracellular pH values are normally regulated within narrow limits. The regulatory mechanisms proposed involve the metabolic consumption of OH& and the active efflux of H +. The evidence for intracellular pH modification in response to CO2 hydration and the production of HCO?3 and H+ is examined. Theoretical calculations and experimental data indicate that CO2 concentrations as high as 5% will lower intracellular pH. Conversely, variation in CO2 levels around atmospheric concentrations is unlikely to perturb intracellular pH. High CO2 levels are found in bulky tissues, and flooded root systems. Evidence is presented that the slow diffusion of dissolved CO2 compared to gaseous CO2 results in its accumulation. It is proposed that the accumulation of respiratory CO2 may reduce intracellular pH values when plant tissues, cells or protoplasts are maintained in a liquid culture medium. Finally, the possible role of dark CO2 fixation and organic acid synthesis in the regulation of intracellular pH is examined. 相似文献
19.
Two succulents with similar growth forms but different types of photosynthesis, Cotyledon orbiculata (crassulacean acid metabolism, CAM) and Othonna opima (C3 pathway), were investigated with respect to the modulation of water use efficiency (WUE) during the transition from the rainy season to subsequent drought. Environmental conditions were simulated in a controlled-environment experiment on the basis of data collected in the habitat of the two species in the southern Namib desert. Experiments included one or more periods of hot bergwind, which frequently occurs in this region. When water was readily available, daily net CO2 fixation was similar in the two species. This result confirms that the daily CO2 fixation of CAM plants is as high as that of morphologically similar C3 plants adapted to the same habitat. As expected, both species reduced CO2 fixation and water loss through transpiration during simulated hot bergwind periods and their WUE values increased. However, after the second hot bergwind period, nearly identical WUEs were recorded: 41.0 and 40.0 mmol mol?1 for C. orbiculata and O. opima, respectively. Therefore the statement that a CAM plant is a better ‘water saver’ than a C3 plant does not necessarily hold for CAM and C3 plants with similar growth forms growing under the same environmental conditions. 相似文献
20.
It is usually thought that unlike terrestrial plants, phytoplankton will not show a significant response to an increase of atmospheric CO2. Here we suggest that this view may be biased by a neglect of the effects of carbon (C) assimilation on the pH and the dissociation of the C species. We show that under eutrophic conditions, productivity may double as a result of doubling of the atmospheric CO2 concentration. Although in practice productivity increase will usually be less, we still predict a productivity increase of up to 40% in marine species with a low affinity for bicarbonate. In eutrophic freshwater systems doubling of atmospheric CO2 may result in an increase of the productivity of more than 50%. Freshwaters with low alkalinity appeared to be very sensitive to atmospheric CO2 elevation. Our results suggest that the aquatic C sink may increase more than expected, and that nuisance phytoplankton blooms may be aggravated at elevated atmospheric CO2 concentrations. 相似文献