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1.
Measurement of spectral reflectance provides a fast and nondestructive method of stress detection in vegetation. In this shallow subsurface CO 2 release experiment to simulate CO 2 leakage of geologically sequestered CO 2, the radiometric responses of plants to elevated soil CO 2 concentration were monitored using a spectroradiometer. Spectral responses included increased reflectance in the visible spectral region and decreased reflectance in the near-infrared region and thus an altered spectral pattern of vegetation. Visible responses of vegetation include purple discoloration and eventual death of leaves at sites where the soil CO 2 concentration was very high. Derivative analysis identified two features (minimum and maximum) in the 575–580 nm and 720–723 nm spectral regions. The normalized difference first derivative index (NFDI) was defined based on the spectral derivative at the two bands. Four vegetation indices were analyzed with the accumulated soil CO 2 concentration to assess the accumulated impact of high soil CO 2 concentration on vegetation. Results show that with increased soil CO 2 concentration due to the surface CO 2 leakage, (1) the structural independent pigment index (SIPI) increased, indicating a high carotenoid to chlorophyll ratio; (2) the chlorophyll normalized difference vegetation index (Chl NDI) decreased, suggesting a decrease in chlorophyll content with time; (3) pigment specific simple ratios (both PSSR a and PSSR b) were reduced for stressed vegetation compared to that at the control site, indicating a reduction in both chlorophyll a and chlorophyll b; and (4) NFDI was low where plants were stressed. Changes in NFDI during the experiment were 36% and 1% for stressed and control plants, respectively. All four indices were found to be sensitive to stress in vegetation induced by high soil CO 2 concentration. 相似文献
2.
Maize and grain sorghum seeds were sown in pots and grown for 39 days in sunlit controlled-environment chambers at 360 (ambient) and 720 (double-ambient, elevated) μmol mol −1 carbon dioxide concentrations [CO 2]. Canopy net photosynthesis (PS) and evapotranspiration (TR) was measured throughout and summarized daily from 08:00 to 17:00 h Eastern Standard Time. Irrigation was withheld from matched pairs of treatments starting on 26 days after sowing (DAS). By 35 DAS, cumulative PS of drought-stress maize, compared to well-watered plants, was 41% lower under ambient [CO 2] but only 13% lower under elevated [CO 2]. In contrast, by 35 DAS, cumulative PS of drought-stress grain sorghum, compared to well-watered plants, was only 9% lower under ambient [CO 2] and 7% lower under elevated [CO 2]. During the 27-35 DAS drought period, water use efficiency (WUE, mol CO 2 Kmol −1 H 2O), was 3.99, 3.88, 5.50, and 8.65 for maize and 3.75, 4.43, 5.26, and 9.94 for grain sorghum, for ambient-[CO 2] well-watered, ambient-[CO 2] stressed, elevated-[CO 2] well-watered and elevated-[CO 2] stressed plants, respectively. Young plants of maize and sorghum used water more efficiently at elevated [CO 2] than at ambient [CO 2], especially under drought. Reductions in biomass by drought for young maize and grain sorghum plants were 42 and 36% at ambient [CO 2], compared to 18 and 14% at elevated [CO 2], respectively. Results of our water stress experiment demonstrated that maintenance of relatively high canopy photosynthetic rates in the face of decreased transpiration rates enhanced WUE in plants grown at elevated [CO 2]. This confirms experimental evidence and conceptual models that suggest that an increase of intercellular [CO 2] (or a sustained intercellular [CO 2]) in the face of decreased stomatal conductance results in relative increases of growth of C 4 plants. In short, drought stress in C 4 crop plants can be ameliorated at elevated [CO 2] as a result of lower stomatal conductance and sustaining intercellular [CO 2]. Furthermore, less water might be required for C 4 crops in future higher CO 2 atmospheres, assuming weather and climate similar to present conditions. 相似文献
3.
Below-ground carbon dioxide (CO 2) emissions occur naturally at CO 2 springs, but the risk of occurrence at other sites will increase as geologic CO 2 storage is implemented to help mitigate climate change. This investigation examines the effects of elevated soil CO 2 concentrations from such emissions on vegetation biomass and microbial community biomass, respiration and carbon utilisation in temperate grassland. Soil CO 2 concentrations was increased by release of concentrated CO 2 gas from a point source 0.6 m below the surface of the soil as a low-level leak (1 l min ?1) for 10 weeks. The gassing resulted in reduced vegetation above- and below-ground biomass over time. No significant changes in microbial biomass or carbon utilisation were observed, but a trend towards reduced microbial respiration was apparent. This research provides a first step towards understanding the potential ecological risks of geologic carbon storage, the development of biological leak detection methods, and improved understanding of the effects of elevated soil CO 2 concentrations on biological communities. 相似文献
4.
Plant responses to elevated CO 2 and high temperature are critically regulated through a complex network of phytohormones and redox homeostasis. However, the involvement of abscisic acid (ABA) in plant adaptation to heat stress under elevated CO 2 conditions has not been thoroughly studied. This study investigated the interactive effects of elevated CO 2 (800 μmol·mol ?1) and heat stress (42 °C for 24 h) on the endogenous level of ABA and the cellular redox state of two genotypes of tomato with different ABA biosynthesis capacities. Heat stress significantly decreased maximum photochemical efficiency of PSII (Fv/Fm) and leaf water potential, but also increased levels of malondialdehyde (MDA) and electrolyte leakage (EL) in both genotypes. Heat‐induced damage was more severe in the ABA‐deficient mutant notabilis ( not) than in its parental cultivar Ailsa Craig ( Ailsa), suggesting that a certain level of endogenous ABA is required to minimise the heat‐induced oxidative damage to the photosynthetic apparatus. Irrespective of genotype, the enrichment of CO 2 remarkably stimulated Fv/Fm, MDA and EL in heat‐stressed plants towards enhanced tolerance. In addition, elevated CO 2 significantly strengthened the antioxidant capacity of heat‐stressed tomato seedlings towards a reduced cellular redox state for a prolonged period, thereby mitigating oxidative stress. However, elevated CO 2 and heat stress did not alter the endogenous level of ABA or the expression of its biosynthetic gene NCED2 in either genotype, indicating that ABA is not involved in elevated CO 2‐induced heat stress alleviation. The results of this study suggest that elevated CO 2 alleviated heat stress through efficient regulation of the cellular redox poise in an ABA‐independent manner in tomato plants. 相似文献
5.
The long-term interaction between elevated CO 2 and soil water deficit was analysed in N 2-fixing alfalfa plants in order to assess the possible drought tolerance effect of CO 2. Elevated CO 2 could delay the onset of drought stress by decreasing transpiration rates, but this effect was avoided by subjecting plants to the same soil water content. Nodulated alfalfa plants subjected to ambient (400 μmol mol ?1) or elevated (700 μmol mol ?1) CO 2 were either well watered or partially watered by restricting water to obtain 30% of the water content at field capacity (ampproximately 0.55 g water cm ?3). The negative effects of soil water deficit on plant growth were counterbalanced by elevated CO 2. In droughted plants, elevated CO 2 stimulated carbon fixation and, as a result, biomass production was even greater than in well-watered plants grown in ambient CO 2. Below-ground production was preferentially stimulated by elevated CO 2 in droughted plants, increasing nodule biomass production and the availability of photosynthates to the nodules. As a result, total nitrogen content in droughted plants was higher than in well-watered plants grown in ambient CO 2. The beneficial effect of elevated CO 2 was not correlated with a better plant water status. It is concluded that elevated CO 2 enhances growth of droughted plants by stimulating carbon fixation, preferentially increasing the availability of photosynthates to below-ground production (roots and nodules) without improving water status. This means that elevated CO 2 enhances the ability to produce more biomass in N 2-fixing alfalfa under given soil water stress, improving drought tolerance. 相似文献
6.
We analysed the impact of elevated CO 2 on water relations, water use efficiency and photosynthetic gas exchange in barley ( Hordeum vulgare L.) under wet and drying soil conditions. Soil moisture was less depleted under elevated compared to ambient [CO 2]. Elevated CO 2 had no significant effect on the water relations of irrigated plants, except on whole plant hydraulic conductance, which was markedly decreased at elevated compared to ambient CO 2 concentrations. The values of relative water content, water potential and osmotic potential were higher under elevated CO 2 during the entire drought period. The better water status of water-limited plants grown at elevated CO 2 was the result of stomatal control rather than of osmotic adjustment. Despite the low stomatal conductance produced by elevated CO 2, net photosynthesis was higher under elevated than ambient CO 2 concentrations. With water shortage, photosynthesis was maintained for longer at higher rates under elevated CO 2. The reduction of stomatal conductance and therefore transpiration, and the enhancement of carbon assimilation by elevated CO 2, increased instantaneous and whole plant water use efficiency in both irrigated and droughted plants. Thus, the metabolism of barley plants grown under elevated CO 2 and moderate or mild water deficit conditions is benefited by increased photosynthesis and lower transpiration. The reduction in plant water use results in a marked increase in soil water content which delays the onset and severity of water deficit. 相似文献
7.
In general, C 3 plant species are more responsive to atmospheric carbon dioxide (CO 2) enrichment than C 4-plants. Increased relative growth rate at elevated CO 2 primarily relates to increased Net Assimilation Rate (NAR), and enhancement of net photosynthesis and reduced photorespiration. Transpiration and stomatal conductance decrease with elevated CO 2, water use efficiency and shoot water potential increase, particularly in plants grown at high soil salinity. Leaf area per plant and leaf area per leaf may increase in an early growth stage with increased CO 2, after a period of time Leaf Area Ratio (LAR) and Specific Leaf Area (SLA) generally decrease. Starch may accumulate with time in leaves grown at elevated CO 2. Plants grown under salt stress with increased (dark) respiration as a sink for photosynthates, may not show such acclimation to increased atmospheric CO 2 levels. Plant growth may be stimulated by atmospheric carbon dioxide enrichment and reduced by enhanced UV-B radiation but the limited data available on the effect of combined elevated CO 2 and ultraviolet B (280–320 nm) (UV-B) radiation allow no general conclusion. CO 2-induced increase of growth rate can be markedly modified at elevated UV-B radiation. Plant responses to elevated atmospheric CO 2 and other environmental factors such as soil salinity and UV-B tend to be species-specific, because plant species differ in sensitivity to salinity and UV-B radiation, as well as to other environmental stress factors (drought, nutrient deficiency). Therefore, the effects of joint elevated atmospheric CO 2 and increased soil salinity or elevated CO 2 and enhanced UV-B to plants are physiologically complex. 相似文献
8.
With the changing climate, plants will be facing increasingly harsh environmental conditions marked by elevated salinity in the soils and elevated concentrations of CO 2 in the atmosphere. These two factors have opposite effects on water status in plants. Therefore, our objective was to determine the interaction between these two factors and to determine whether elevated [CO 2] might alleviate the adverse effects of salt stress on water status in two barley cultivars, Alpha and Iranis, by studying their relative water content and their water potential and its components, transpiration rate, hydraulic conductance, and water use efficiency. Both cultivars maintained their water status under salt stress, increasing water use efficiency and conserving a high relative water content by (1) reducing water potential via passive dehydration and active osmotic adjustment and (2) decreasing transpiration through stomatal closure and reducing hydraulic conductance. Iranis showed a greater capacity to achieve osmotic adjustment than Alpha. Under the combined conditions of salt-stress and elevated [CO 2], both cultivars (1) achieved osmotic adjustment to a greater extent than at ambient [CO 2], likely due to elevated rates of photosynthesis, and (2) decreased passive dehydration by stomatal closure, thereby maintaining a greater turgor potential, relative water content, and water use efficiency. Therefore, we found an interaction between salt stress and elevated [CO 2] with regard to water status in plants and found that elevated [CO 2] is associated with improved water status of salt-stressed barley plants. 相似文献
9.
This study was conducted to determine the response in leaf growth and gas exchange of soybean ( Glycine max Merr.) to the combined effects of water deficits and carbon dioxide (CO 2) enrichment. Plants grown in pots were allowed to develop initially in a glasshouse under ambient CO 2 and well-watered conditions. Four-week old plants were transferred into two different glasshouses with either ambient (360 μmol mol -1) or elevated (700 μmol mol -1) CO 2. Following a 2-day acclimation period, the soil of the drought-stressed pots was allowed to dry slowly over a 2-week period. The stressed pots were watered daily so that the soil dried at an equivalent rate under the two CO 2 levels. Elevated [CO 2] decreased water loss rate and increased leaf area development and photosynthetic rate under both well-watered and drought-stressed conditions. There was, however, no significant effect of [CO 2] in the response relative to soil water content of normalized leaf gas exchange and leaf area. The drought response based on soil water content for transpiration, leaf area, and photosynthesis provide an effective method for describing the responses of soybean physiological processes to the available soil water, independent of [CO 2]. 相似文献
10.
With the changing climate, plants will be facing increasingly harsh environmental conditions marked by elevated salinity in the soils and elevated concentrations of CO 2 in the atmosphere. These two factors have opposite effects on water status in plants. Therefore, our objective was to determine the interaction between these two factors and to determine whether elevated [CO 2] might alleviate the adverse effects of salt stress on water status in two barley cultivars, Alpha and Iranis, by studying their relative water content and their water potential and its components, transpiration rate, hydraulic conductance, and water use efficiency. Both cultivars maintained their water status under salt stress, increasing water use efficiency and conserving a high relative water content by (1) reducing water potential via passive dehydration and active osmotic adjustment and (2) decreasing transpiration through stomatal closure and reducing hydraulic conductance. Iranis showed a greater capacity to achieve osmotic adjustment than Alpha. Under the combined conditions of salt-stress and elevated [CO 2], both cultivars (1) achieved osmotic adjustment to a greater extent than at ambient [CO 2], likely due to elevated rates of photosynthesis, and (2) decreased passive dehydration by stomatal closure, thereby maintaining a greater turgor potential, relative water content, and water use efficiency. Therefore, we found an interaction between salt stress and elevated [CO 2] with regard to water status in plants and found that elevated [CO 2] is associated with improved water status of salt-stressed barley plants. 相似文献
11.
This study examines the extent to which the predicted CO 2‐protective effects on the inhibition of growth, impairment of photosynthesis and nutrient imbalance caused by saline stress are mediated by an effective adaptation of the endogenous plant hormonal balance. Therefore, sweet pepper plants ( Capsicum annuum, cv. Ciclón) were grown at ambient or elevated [CO 2] (400 or 800 µmol mol –1) with a nutrient solution containing 0 or 80 m M NaCl. The results show that, under saline conditions, elevated [CO 2] increased plant dry weight, leaf area, leaf relative water content and net photosynthesis compared with ambient [CO 2], whilst the maximum potential quantum efficiency of photosystem II was not modified. In salt‐stressed plants, elevated [CO 2] increased leaf NO 3– concentration and reduced Cl – concentration. Salinity stress induced ABA accumulation in the leaves but it was reduced in the roots at high [CO 2], being correlated with the stomatal response. Under non‐stressed conditions, IAA was dramatically reduced in the roots when high [CO 2] was applied, which resulted in greater root DW and root respiration. Additionally, the observed high CK concentration in the roots (especially tZR) could prevent downregulation of photosynthesis at high [CO 2], as the N level in the leaves was increased compared with the ambient [CO 2], under salt‐stress conditions. These results demonstrate that the hormonal balance was altered by the [CO 2], which resulted in significant changes at the growth, gas exchange and nutritional levels. 相似文献
12.
The extent and occurrence of water stress-induced “patchy” CO 2 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]CO 2 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 CO 2 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 CO 2 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 [CO 2] in stressed bean leaves. When extent of heterogenous CO 2 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 CO 2 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
13.
Summary The effects of CO 2 enrichment and water stress on gas exchange of Liquidambar styraciflua L. (sweetgum) and Pinus taeda L. (loblolly pine) seedlings were examined for individuals grown from seed under high (1000 mol·m -2·s -1) and low (250 mol·m -2·s -1) photosynthetic photon flux density at 350, 675 and 1000 l·l -1 CO 2. At 8 weeks of age, half the seedlings in each CO 2-irradiance treatment were subjected to a drying cycle which reduced plant water potential to about -2.5 MPa in the most stressed plants, while control plants remained well-watered (water potentials of -0.3 and -0.7 MPa for sweetgum and loblolly pine, respectively). During this stress cycle, whole seedling net photosynthesis, transpiration and stomatal conductance of plants from each CO 2-irradiance-water treatment were measured under respective growth conditions.For both species, water stress effects on gas exchange were greatest under high irradiance conditions. Waterstressed plants had significantly lower photosynthesis rates than well-watered controls throughout most of the drying cycle, with the most severe inhibition occurring for low CO 2, high irradiance-grown sweetgum seedlings. Carbon dioxide enrichment had little effect on gas exchange rates of either water-stressed or well-watered loblolly pine seedlings. In contrast, water stress effects were delayed for sweetgum seedlings grown at elevated CO 2, particularly in the 1000 l·l -1 CO 2, high irradiance treatment where net photosynthesis, transpiration and conductance of stressed plants were 60, 36 and 33% of respective control values at the end of the drying cycle. Development of internal plant water deficits was slower for stressed sweetgum seedlings grown at elevated CO 2. As a result, these seedlings maintained higher photosynthetic rates over the drying cycle than stressed sweetgum seedlings grown at 350 l·l -1 CO 2 and stressed loblolly pine seedlings grown at ambient and enriched CO 2 levels. In addition, water-stressed sweetgum seedlings grown at elevated CO 2 exhibited a substantial increase in water use efficiency.The results suggest that with the future increase in atmospheric CO 2 concentration, sweetgum seedlings should tolerate longer exposure to low soil moisture, resulting in greater first year survival of seedlings on drier sites of abandoned fields in the North Carolina piedmont. 相似文献
14.
We determined evapotranspiration in three experiments designed to study the effects of elevated CO 2 and increased N deposition on ombrotrophic bog vegetation. Two experiments used peat monoliths with intact bog vegetation in containers, with one experiment outdoors and the other in a greenhouse. A third experiment involved monocultures and mixtures of Sphagnum magellanicum and Eriophorum angustifolium in containers in the same greenhouse. To determine water use of the bog vegetation in July–August for each experiment and each year we measured water inputs and outputs from the containers. We studied the effects of elevated CO 2 and N supply on evapotranspiration in relation to vascular plant biomass and exposure of the moss surface (measured as height of the moss surface relative to the container edge). Elevated CO 2 reduced water use of the bog vegetation in all three experiments, but the CO 2 effect on evapotranspiration interacted with vascular plant biomass and exposure of the moss surface. Evapotranspiration in the outdoor experiment was largely determined by evaporation from the Sphagnum moss surface (as affected by exposure to wind) and less so by vascular plant transpiration. Nevertheless, elevated CO 2 significantly reduced evapotranspiration by 9–10% in the outdoor experiment. Vascular plants reduced evapotranspiration in the outdoor experiment, but increased water use in the greenhouse experiments. The relation between vascular plant abundance and evapotranspiration appears to depend on wind conditions; suggesting that vascular plants reduce water losses mainly by reducing wind speed at the moss surface. Sphagnum growth is very sensitive to changes in water level; low water availability can have deleterious effects. As a consequence, reduced evapotranspiration in summer, whether caused by elevated CO 2 or by small increases in vascular plant cover, is expected to favour Sphagnum growth in ombrotrophic bog vegetation. 相似文献
15.
Isoprene is the most abundant biogenic hydrocarbon released from vegetation and it plays a major role in tropospheric chemistry. Because of its link to climate change, there is interest in understanding the relationship between CO 2, water availability and isoprene emission. We explored the effect of atmospheric elevated CO 2 concentration and its interaction with vapour pressure deficit (VPD) and water stress, on gross isoprene production (GIP) and net ecosystem exchange of CO 2 (NEE) in two Populus deltoides plantations grown at ambient and elevated atmospheric CO 2 concentration in the Biosphere 2 Laboratory facility. Although GIP and NEE showed a similar response to light and temperature, their responses to CO 2 and VPD were opposite; NEE was stimulated by elevated CO 2 and depressed by high VPD, while GIP was inhibited by elevated CO 2 and stimulated by high VPD. The difference in response between isoprene production and photosynthesis was also evident during water stress. GIP was stimulated in the short term and declined only when the stress was severe, whereas NEE started to decrease from the beginning of the experiment. This contrasting response led the carbon lost as isoprene in both the ambient and the elevated CO 2 treatments to increase as water stress progressed. Our results suggest that water limitation can override the inhibitory effect of elevated CO 2 leading to increased global isoprene emissions in a climate change scenario with warmer and drier climate. 相似文献
16.
Aims Anthropogenic release of CO 2 is an important factor in the continuing rise in mean global temperature. Carbon capture and storage (CCS) offers a promising technology to capture and sequester CO 2 in deep geological reservoirs. In view of the possible impact of leakage from CCS systems on vegetation, we examined the effects of elevated soil [CO 2] on growth and yield in Zea mays L. Methods Maize was exposed to elevated soil [CO 2] by injecting CO 2 at controlled rates using a purpose-designed field exposure facility. Results Measurements of soil [CO 2] and [O 2] revealed a strong negative correlation. Plants in a 40–90 cm diameter area centred on the injection point showed reduced growth and progressive development of severe stress symptoms during the gassing period. All above-ground vegetative (shoot, stem and leaf weight plant -1, chlorophyll content) and reproductive growth variables examined (mature cob and seed numbers plant -1) were negatively correlated with soil [CO 2] and positively correlated with soil [O 2]. Plants exposed to the highest [CO 2] produced adventitious roots, possibly as an adaptive response to hypoxic soil conditions. Conclusions Leakage from CCS transport or storage sites may have strong localised negative impacts on surface vegetation, the extent of which differs greatly between species. 相似文献
17.
Soybean ( Glycine max L. Merrill cv `Bragg') plants were grown in pots at six elevated atmospheric CO 2 concentrations and two watering regimes in open top field chambers to characterize leaf xylem potential, stomatal resistance and conductance, transpiration, and carbohydrate contents of the leaves in response to CO 2 enrichment and water stress conditions. Groups of plants at each CO 2 concentration were subjected to water stress by withholding irrigation for 4 days during the pod-filling stage. Under well watered conditions, the stomatal conductance of the plants decreased with increasing CO2 concentration. Therefore, although leaf area per plant was greater in the high CO2 treatments, the rate of water loss per plant decreased with CO2 enrichment. After 4 days without irrigation, plants in lower CO2 treatments showed greater leaf tissue damage, lower leaf water potential, and higher stomatal resistance than high CO2 plants. Stomatal closure occurred at lower leaf water potentials for the low CO2 grown plants than the high CO2 grown plants. Significantly greater starch concentrations were found in leaves of high CO2 plants, and the reductions in leaf starch and increases in soluble sugars due to water stress were greater for low CO2 plants. The results showed that even though greater growth was observed at high atmospheric CO2 concentrations, lower rates of water use delayed and, thereby, prevented the onset of severe water stress under conditions of low moisture availability. 相似文献
18.
Photosynthesis in C 3 plants is CO 2 limited and therefore any increase in Rubisco carboxylation substrate may increase net CO 2 fixation, unless plants experience acclimation or other limitations. These aspects are largely unexplored in grapevine. Photosynthesis analysis was used to assess the stomatal, mesophyll, photochemical and biochemical contributions to the decreasing photosynthesis observed in Tempranillo grapevines ( Vitis vinifera) from veraison to ripeness, modulated by CO 2, temperature and water availability. Photosynthesis and photosystem II photochemistry decreased from veraison to ripeness. The elevated CO 2 and temperature increased photosynthesis, but transiently, in both well irrigated (WI) and water‐stressed plants. Photosynthetic rates were maxima 1 week after the start of elevated CO 2 and temperature treatments, but differences with treatments of ambient conditions disappeared with time. There were not marked changes in leaf water status, leaf chlorophyll or leaf protein that could limit photosynthesis at ripeness. Leaf total soluble sugars remained at ripeness as high as 2 weeks after the start of treatments. On the other hand, and as expected, CO 2 diffusional limitations impaired photosynthesis in grapevine plants grown under water scarcity, stomatal and mesophyll conductances to CO 2 decreased and in turn low chloroplastic CO 2 concentrations limited photosynthetic CO 2 fixation. In summary, photochemistry and photosynthesis from veraison to ripeness in Tempranillo grapevine were dominated by a developmental‐related decreasing trend that was only transiently influenced by elevated CO 2 concentrations. 相似文献
19.
Weather events such as drought and elevated atmospheric CO 2 are likely to interact with plants in numerous ways with diverse mechanisms. As a consequence of changes in quality of plants, the performance parameters and population dynamics of herbivores are expected to be influenced. In this study, a split-plot design was used to evaluate the interaction of elevated CO 2 and irrigation regime on population growth of the two-spotted spider mite, Tetranychus urticae Koch (Tetranychidae: Tetranychini), feeding on sweet pepper, Capsicum annum L. (Solanaceae), in environmentally controlled chambers. Results showed that exposure to elevated CO 2 significantly increased the C/N ratio in sweet pepper plants. Except in case of the adult stage, elevated CO 2 did not significantly increase the population density of other developmental stages or the overall population of T. urticae. However, water stress by itself and in combination with elevated CO 2 had significant effects on per capita population growth rate (r) and population density of mites. Maximum growth rate and population density of mites were observed at a combination of elevated CO 2 and intermediate water stress. Further studies, especially in field conditions, investigating the impact of elevated CO 2 and water stress on population size and growth of herbivores in other plant species may contribute to a greater understanding of the implications of global climate change on future crop productivity. 相似文献
20.
Terrestrial plant and soil respiration, or ecosystem respiration (R eco), represents a major CO 2 flux in the global carbon cycle. However, there is disagreement in how R eco will respond to future global changes, such as elevated atmosphere CO 2 and warming. To address this, we synthesized six years (2007–2012) of R eco data from the Prairie Heating And CO 2 Enrichment (PHACE) experiment. We applied a semi‐mechanistic temperature–response model to simultaneously evaluate the response of R eco to three treatment factors (elevated CO 2, warming, and soil water manipulation) and their interactions with antecedent soil conditions [e.g., past soil water content (SWC) and temperature (SoilT)] and aboveground factors (e.g., vapor pressure deficit, photosynthetically active radiation, vegetation greenness). The model fits the observed R eco well ( R2 = 0.77). We applied the model to estimate annual (March–October) R eco, which was stimulated under elevated CO 2 in most years, likely due to the indirect effect of elevated CO 2 on SWC. When aggregated from 2007 to 2012, total six‐year R eco was stimulated by elevated CO 2 singly (24%) or in combination with warming (28%). Warming had little effect on annual R eco under ambient CO 2, but stimulated it under elevated CO 2 (32% across all years) when precipitation was high (e.g., 44% in 2009, a ‘wet’ year). Treatment‐level differences in R eco can be partly attributed to the effects of antecedent SoilT and vegetation greenness on the apparent temperature sensitivity of R eco and to the effects of antecedent and current SWC and vegetation activity (greenness modulated by VPD) on R eco base rates. Thus, this study indicates that the incorporation of both antecedent environmental conditions and aboveground vegetation activity are critical to predicting R eco at multiple timescales (subdaily to annual) and under a future climate of elevated CO 2 and warming. 相似文献
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