共查询到20条相似文献,搜索用时 15 毫秒
1.
Summary
Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650 l l –1 and two levels of soil nutrition. In the high nutrient treatment, increasing CO 2 led to a doubling of shoot mass, whereas nutrient limitation completely constrained the response to elevated CO 2. Root biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide enrichment but increased under low nutrient availability, thus the ratio was apparently controlled by changes in carbon allocation to shoot mass alone. Growth under CO 2 enrichment increased the starch concentrations of leaves grown under both nutrient regimes, while increased CO 2 and low nutrient availability acted in concert to reduce leaf nitrogen concentration and water content. Carbon dioxide enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate versus nitrogen (C/N). The two treatment effects were significantly interactive in that nutrient limitation slightly reduced the C/N balance among the high-CO 2 plants. Leaf volatile terpene concentration increased only in the nutrient limited plants and did not follow the overall increase in leaf C/N ratio. Grasshopper consumption was significantly greater on host leaves grown under CO 2 enrichment but was reduced on leaves grown under low nutrient availability. An overall negative relationship of consumption versus leaf volatile concentration suggests that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hosts. Digestibility of host leaves grown under the high CO 2 treatment was significantly increased and was related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced by the nutrient limitation treatment but co-varied with leaf water content. 相似文献
2.
The effect of drought on the photosynthetic functioning of two C 3 plants, Phaseolus vulgaris and Elatostema repens, has been examined. Leaf net CO 2 uptake measured in normal air was negligible at a leaf water deficit of about 30% while the calculated leaf intercellular CO 2 concentration (Ci) was unchanged. However, both the maximal photosynthetic capacity (CO 2-dependent O 2 evolution) and apparent quantum yield, measured in the presence of saturating CO 2 levels (5 to 14%), only started to decrease within the range of 25 to 30% leaf water deficit. This shows that the drought-induced inhibition seen in normal air is not caused by an inhibition of the photosynthetic mechanism, and that in this case Ci values can be misleading. Both 77 K and room-temperature fluorescence measurements indicate that the functioning of the photosystem-II reaction centre is hardly modified by water shortage. Furthermore, an analysis of photochemical chlorophyll fluorescence quenching shows, in the absence of CO 2, that O 2 can be an efficient acceptor of photosynthetic energy, even in severly dehydrated plants which do not show net CO 2 uptake in normal air. In these plants, O 2 is probably reduced mainly via Mehler-type reactions. High-light treatment given at low O 2 increases photoinhibition as measured by the decrease of apparent quantum yield in dehydrated P. vulgaris, whereas, interestingly, 1% O 2 protects dehydrated E. repens against high-light damage. The two plants could have different protective mechanisms depending upon the O 2 level or different photoinhibitory sites or mechanisms.Abbreviations and symbols Ca, Ci
ambient and calculated intercellular CO 2 concentration
- Fm, Fo, Fv
maximum, initial and variable fluorescence emission
- LWD
leaf water deficit
- PPFD
photosynthetic photon flux density
- PSII
photosystem II
- qQ
photochemical quenching of chlorophyll fluorescence 相似文献
3.
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
4.
Soil N availability may play an important role in regulating the long-term responses of plants to rising atmospheric CO 2 partial pressure. To further examine the linkage between above- and belowground C and N cycles at elevated CO 2, we grew clonally propagated cuttings of Populus grandidentata in the field at ambient and twice ambient CO 2 in open bottom root boxes filled with organic matter poor native soil. Nitrogen was added to all root boxes at a rate equivalent
to net N mineralization in local dry oak forests. Nitrogen added during August was enriched with 15N to trace the flux of N within the plant-soil system. Above-and belowground growth, CO 2 assimilation, and leaf N content were measured non-destructively over 142 d. After final destructive harvest, roots, stems,
and leaves were analyzed for total N and 15N.
There was no CO 2 treatment effect on leaf area, root length, or net assimilation prior to the completion of N addition. Following the N addition,
leaf N content increased in both CO 2 treatments, but net assimilation showed a sustained increase only in elevated CO 2 grown plants. Root relative extension rate was greater at elevated CO 2, both before and after the N addition. Although final root biomass was greater at elevated CO 2, there was no CO 2 effect on plant N uptake or allocation. While low soil N availability severely inhibited CO 2 responses, high CO 2 grown plants were more responsive to N. This differential behavior must be considered in light of the temporal and spatial
heterogeneity of soil resources, particularly N which often limits plant growth in temperate forests. 相似文献
5.
Plants may be more sensitive to carbon dioxide (CO 2) enrichment at subambient concentrations than at superambient concentrations, but field tests are lacking. We measured soil‐water content and determined xylem pressure potentials and δ 13C values of leaves of abundant species in a C3/C4 grassland exposed during 1997–1999 to a continuous gradient in atmospheric CO 2 spanning subambient through superambient concentrations (200–560 µmol mol 2?1). We predicted that CO 2 enrichment would lessen soil‐water depletion and increase xylem potentials more over subambient concentrations than over superambient concentrations. Because water‐use efficiency of C3 species (net assimilation/leaf conductance; A/g) typically increases as soils dry, we hypothesized that improvements in plant‐water relations at higher CO 2 would lessen positive effects of CO 2 enrichment on A/g. Depletion of soil water to 1.35 m depth was greater at low CO 2 concentrations than at higher CO 2 concentrations during a mid‐season drought in 1998 and during late‐season droughts in 1997 and 1999. During droughts each year, mid‐day xylem potentials of the dominant C4 perennial grass ( Bothriochloa ischaemum (L.) Keng) and the dominant C3 perennial forb ( Solanum dimidiatum Raf.) became less negative as CO 2 increased from subambient to superambient concentrations. Leaf A/g—derived from leaf δ 13C values—was insensitive to feedbacks from CO 2 effects on soil water and plant water. Among most C3 species sampled—including annual grasses, perennial grasses and perennial forbs—A/g increased linearly with CO 2 across subambient concentrations. Leaf and air δ 13C values were too unstable at superambient CO 2 concentrations to reliably determine A/g. Significant changes in soil‐ and plant‐water relations over subambient to superambient concentrations and in leaf A/g over subambient concentrations generally were not greater over low CO 2 than over higher CO 2. The continuous response of these variables to CO 2 suggests that atmospheric change has already improved water relations of grassland species and that periodically water‐limited grasslands will remain sensitive to CO 2 enrichment. 相似文献
6.
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
7.
We studied the responses of leaf water potential (Ψ w), morphology, biomass accumulation and allocation, and canopy productivity index (CPI) to the combined effects of elevated
CO 2 and drought stress in Caragana intermedia seedlings. Seedlings were grown at two CO 2 concentrations (350 and 700 μmol mol −1) interacted with three water regimes (60–70%, 45–55%, and 30–40% of field capacity of soil). Elevated CO 2 significantly increased Ψ w, decreased specific leaf area (SLA) and leaf area ratio (LAR) of drought-stressed seedlings, and increased tree height, basal
diameter, shoot biomass, root biomass as well as total biomass under the all the three water regimes. Growth responses to
elevated CO 2 were greater in well-watered seedlings than in drought-stressed seedlings. CPI was significantly increased by elevated CO 2, and the increase in CPI became stronger as the level of drought stress increased. There were significant interactions between
elevated CO 2 and drought stress on leaf water potential, basal diameter, leaf area, and biomass accumulation. Our results suggest that
elevated CO 2 may enhance drought avoidance and improved water relations, thus weakening the effect of drought stress on growth of C. intermedia seedings. 相似文献
8.
Long-term exposure to elevated CO 2 concentration will affect the traits of wild plants in association with other environmental factors. We investigated multiple
effects of atmospheric CO 2 concentration, irradiance, and soil N availability on the leaf photosynthetic traits of a herbaceous species, Polygonum sachalinense, growing around natural CO 2 springs in northern Japan. Atmospheric CO 2 concentration and its interaction with irradiance and soil N availability affected several leaf traits. Leaf mass per unit
area increased and N per mass decreased with increasing CO 2 and irradiance. Leaf N per area increased with increasing soil N availability at higher CO 2 concentrations. The photosynthetic rate under growth CO 2 conditions increased with increasing irradiance and CO 2, and with increasing soil N at higher CO 2 concentrations. The maximal velocity of ribulose 1,5-bisphosphate carboxylation ( V
cmax) was affected by the interaction of CO 2 and soil N, suggesting that down-regulation of photosynthesis at elevated CO 2 was more evident at lower soil N availability. The ratio of the maximum rate of electron transport to V
cmax ( J
max/ V
cmax) increased with increasing CO 2, suggesting that the plants used N efficiently for photosynthesis at high CO 2 concentrations by changes in N partitioning. To what extent elevated CO 2 influenced plant traits depended on other environmental factors. As wild plants are subject to a wide range of light and
nutrient availability, our results highlight the importance of these environmental factors when the effects of elevated CO 2 on plants are evaluated. 相似文献
9.
Sour orange ( Citrus aurantium L.) grown in low-P (9–12 ppm) and high-P (420 ppm) soil inoculated with or without Glomus intraradices (G.i.), were evaluated for biomass, carbohydrates, ribulose bisphosphate carboxylase (RuBPCase), phosphoenolpyruvate carboxylase (PEPCase) activity, leaf 14CO 2 incorporation, and other physiological parameters. Growth of plants in the low-P, noninoculated soil was lowest, with total dry biomass reduced up to half of the low-P, inoculum treatment. Total nonstructural carbohydrates were 40% lower in leaves of plants in the low-P, noninoculated soil, compared with the other treatments. Inoculation of the low-P soil enhanced leaf 14CO 2 incorporation by 67%, total chlorophyll content by 28%, and RuBPCase activity by 42%, compared with low-P, noninoculated treatment. Improved P-use efficiency by G.i. in low-P soil was comparable to high-P nutrition in improving leaf 14CO 2 incorporation and concentration of major leaf photosynthetic products that include starch and sucrose. Leaf PEPCase activity in the low-P, noninoculated treatment, however, was at least threefold higher than the other treatments, suggesting a possible alteration in organic acid metabolism in sour orange leaves as a result of P deficiency. 相似文献
10.
The consequences for plant-insect interactions of atmospheric changes in alpine ecosystems are not well understood. Here, we tested the effects of elevated CO 2 on leaf quality in two dwarf shrub species ( Vaccinium myrtillus and V. uliginosum) and the response of the alpine grasshopper ( Miramella alpina) feeding on these plants in a field experiment at the alpine treeline (2,180 m a.s.l.) in Davos, Switzerland. Relative growth rates (RGR) of M. alpina nymphs were lower when they were feeding on V. myrtillus compared to V. uliginosum, and were affected by elevated CO 2 depending on plant species and nymph developmental stage. Changes in RGR correlated with CO 2-induced changes in leaf water, nitrogen, and starch concentrations. Elevated CO 2 resulted in reduced female adult weight irrespective of plant species, and prolonged development time on V. uliginosum only, but there were no significant differences in nymphal mortality. Newly molted adults of M. alpina produced lighter eggs and less secretion (serving as egg protection) under elevated CO 2. When grasshoppers had a choice among four different plant species grown either under ambient or elevated CO 2, V. myrtillus and V. uliginosum consumption increased under elevated CO 2 in females while it decreased in males compared to ambient CO 2-grown leaves. Our findings suggest that rising atmospheric CO 2 distinctly affects leaf chemistry in two important dwarf shrub species at the alpine treeline, leading to changes in feeding behavior, growth, and reproduction of the most important insect herbivore in this system. Changes in plant-grasshopper interactions might have significant long-term impacts on herbivore pressure, community dynamics and ecosystem stability in the alpine treeline ecotone. 相似文献
11.
This work examined the effects of elevated CO 2 and temperature and water regimes, alone and in interaction, on the leaf characteristics [leaf area ( LA), specific leaf weight ( SLW), leaf nitrogen content ( NL) based on LA], photosynthesis (light‐saturated net carbon fixation rate, Psat) and carbon storage in aboveground biomass of leaves ( Cl) and stem ( Cs) for a perennial reed canary grass ( Phalaris arundinacea L., Finnish local cultivar). For this purpose, plants were grown under different water regimes (ranging from high to low soil moisture) in climate‐controlled growth chambers under the elevated CO 2 and/or temperature (following a factorial design) over a whole growing season (May–September in 2009). The results showed that the elevated temperature increased the leaf growth, photosynthesis and carbon storage of aboveground biomass the most in the early growing periods, compared with ambient temperature. However, the plant growth declined rapidly thereafter with a lower carbon storage at the end of growing season. This was related to the accelerated phenology regulation and consequent earlier growth senescence. Consequently, the elevation of CO 2 increased the Psat, LA and SLW during the growing season, with a significant concurrent increase in the carbon storage in aboveground biomass. Low soil moisture decreased the Psat, leaf stomatal conductance, LA and carbon storage in above ground biomass compared with high and normal soil moisture. This water stress effect was the largest under the elevated temperature. The elevated CO 2 partially mitigated the adverse effects of high temperature and low soil moisture. However, the combination of elevated temperature and CO 2 did not significantly increase the carbon storage in aboveground biomass of the plants. 相似文献
12.
Photoinhibition has been often evaluated with leaf discs floated on water or placed on wet papers to prevent desiccation.
Under these conditions, there is a possibility that CO 2 diffusion is blocked by water, which may lead to reduction in photosynthetic CO 2 assimilation. Using Chenopodium album L. grown at two irradiances, photosynthesis, quantum yield of Photosystem II (Δ F/ F
m′), non-photochemical quenching ( qN), and photoinhibition were compared between detached leaves and leaf discs. In low-light-grown plants, photoinhibition was
greater in leaf discs than in detached leaves, while in high-light-grown plants, there was little difference. Leaf discs showed
lower rates of photosynthesis and Δ F/ F
m′, and higher qN. The Δ F/ F
m′ in leaf discs increased when leaf discs were exposed to high concentration of CO 2, suggesting that CO 2 diffusion to chloroplasts was limited in leaf discs floated on water.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Predicted increases in atmospheric CO 2 and global mean temperature may alter important plant-insect associations due to the direct effects of temperature on insect development and the indirect effects of elevated temperature and CO 2 enrichment on phytochemicals important for insect success. We investigated the effects of CO 2 and temperature on the interaction between gypsy moth ( Lymantria dispar L.) larvae and red maple ( Acer rubrum L.) saplings by bagging first instar larvae within open-top chambers at four CO 2/temperature treatments: (1) ambient temperature, ambient CO 2, (2) ambient temperature, elevated CO 2
(+300 l l -1
CO 2), (3) elevated temperature (+3.5°C), ambient CO 2, and (4) elevated temperature, elevated CO 2. Larvae were reared to pupation and leaf samples taken biweekly to determine levels of total N, water, non-structural carbohydrates, and an estimate of defensive phenolic compounds in three age classes of foliage: (1) immature, (2) mid-mature and (3) mature. Elevated growth temperature marginally reduced ( P <0.1) leaf N and significantly reduced ( P <0.05) leaf water across CO 2 treatments in mature leaves, whereas leaves grown at elevated CO 2 concentration had a significant decrease in leaf N and a significant increase in the ratio of starch:N and total non-structural carbohydrates:N. Leaf N and water decreased and starch:N and total non-structural carbohydrates:N ratios increased as leaves aged. Phenolics were unaffected by CO 2 or temperature treatment. There were no interactive effects of CO 2 and temperature on any phytochemical measure. Gypsy moth larvae reached pupation earlier at the elevated temperature (female =8 days,
P <0.07; male =7.5 days,
P <0.03), whereas mortality and pupal fresh weight of insects were unrelated to either CO 2, temperature or their interaction. Our data show that CO 2 or temperature-induced alterations in leaf constituents had no effect on insect performance; instead, the long-term exposure to a 3.5°C increase in temperature shortened insect development but had no effect on pupal weight. It appears that in some tree-herbivorous insect systems the direct effects of an increased global mean temperature may have greater consequences for altering plant-insect interactions than the indirect effects of an increased temperature or CO 2 concentration on leaf constituents. 相似文献
14.
Leaf photosynthesis rate of the C 4 species Paspalum plicatulum Michx was virtually CO 2-saturated at normal atmospheric CO 2 concentration but transpiration decreased as CO 2 was increased above normal concentrations thereby increasing transpiration efficiency. To test whether this leaf response led growth to be CO 2-sensitive when water supply was restricted, plants were grown in sealed pots of soil as miniature swards. Water was supplied either daily to maintain a constant water table, or at three growth restricting levels on a 5-day drying cycle. Plants were either in a cabinet with normal air (340 mol (CO 2) mol -1 (air)) or with 250 mol mol -1 enrichment. Harvesting was by several cycles of defoliation.With abundant water supply high CO 2 concentration did not cause increased growth, but it did not cause an increase in growth over a wide range of growth-limiting water supplies either. Only when water supply was less than 30–50% of the amount used by the stand with a water-table was there evidence that dry weight growth was enhanced by high CO 2. In addition, with successive regrowth, the enhancing effect under a regime of minimal water allocations, became attenuated. Examination of leaf gas exchange, growth and water use data showed that in the long term stomatal conductance responses were of little significance in matching plant water use to low water allocation; regulation of leaf area was the mechanism through which consumption matched supply. Since high CO 2 effects operate principally via stomatal conductance in C 4 species, we postulate that for this species higher CO 2 concentrations expected globally in future will not have much effect on long term growth. 相似文献
15.
Both innate and evolutionarily increased ecophysiological advantages can contribute to vigorous growth, and eventually to
invasiveness of alien plants. Little effort has been made to explore the roles of innate factors of alien plants in invasiveness
and the effects of CO 2 enrichment on alien plant invasions. To address these problems, we compared invasive Eupatorium adenophorum, its native conspecific, and a native congener ( E. japonicum) under ambient and doubled atmospheric CO 2 concentrations. Native E. adenophorum from Mexico grew slower than invasive E. adenophorum but faster than native E. japonicum under both CO 2 concentrations. The faster growth rate of invasive E. adenophorum was associated with higher photosynthetic capacity and leaf area ratio. For invasive E. adenophorum, the higher photosynthetic capacity was associated with higher nitrogen (N) allocation to photosynthesis, which was related
to lower leaf mass per area; the higher leaf area ratio was due to lower leaf mass per area and higher leaf mass fraction.
Tradeoff between N allocations to photosynthesis versus defenses was found. CO 2 enrichment significantly increased relative growth rate and biomass accumulation by increasing actual photosynthetic rate
for all studied materials. However, the relative increase in growth was not significantly different among them. CO 2 enrichment did not influence N allocation to photosynthesis, but increased N allocation to cell walls. The reduced leaf N
content decreased N content in photosynthesis, explaining the down-regulation of photosynthetic capacity under prolonged elevated
CO 2 concentration. Our results indicate that both innate and evolutionary advantages in growth and related ecophysiological traits
contribute to invasiveness of invasive E. adenophorum, and CO 2 enrichment may not aggravate E. adenophroum’s invasion in the future. 相似文献
16.
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
17.
Interactive effects of CO 2 and water availability have been predicted to alter the competitive relationships between C3 and C4 species over geological and contemporary time scales. We tested the effects of drought and CO 2 partial pressures ( pCO 2) ranging from values of the Pleistocene to those predicted for the future on the physiology and growth of model C3 and C4 species. We grew co-occurring Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture at 18 (Pleistocene), 27 (preindustrial), 35 (current), and 70 (future) Pa CO 2 under conditions of high light and nutrient availability. After 27 days of growth, water was withheld from randomly chosen plants of each species until visible wilting occurred. Under well-watered conditions, low pCO 2 that occurred during the Pleistocene was highly limiting to C3 photosynthesis and growth, and C3 plants showed increased photosynthesis and growth with increasing pCO 2 between the Pleistocene and future CO 2 values. Well-watered C4 plants exhibited increased photosynthesis in response to increasing pCO 2, but total mass and leaf area were unaffected by pCO 2. In response to drought, C3 plants dropped a large amount of leaf area and maintained relatively high leaf water potential in remaining leaves, whereas C4 plants retained greater leaf area, but at a lower leaf water potential. Furthermore, drought-treated C3 plants grown at 18 Pa CO 2 retained relatively greater leaf area than C3 plants grown at higher pCO 2 and exhibited a delay in the reduction of stomatal conductance that may have occurred in response to severe carbon limitations. The C4 plants grown at 70 Pa CO 2 showed lower relative reductions in net photosynthesis by the end of the drought compared to plants at lower pCO 2, indicating that CO 2 enrichment may alleviate drought effects in C4 plants. At the Pleistocene pCO 2, C3 and C4 plants showed similar relative recovery from drought for leaf area and biomass production, whereas C4 plants showed higher recovery than C3 plants at current and elevated pCO 2. Based on these model systems, we conclude that C3 species may not have been at a disadvantage relative to C4 species in response to low CO 2 and severe drought during the Pleistocene. Furthermore, C4 species may have an advantage over C3 species in response to increasing atmospheric CO 2 and more frequent and severe droughts. 相似文献
18.
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
19.
Global atmospheric CO 2 is increasing at a rate of 1.5–2 ppm per year and is predicted to double by the end of the next century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of current research. Here we present results from a field study of elevated CO 2 in a California annual grassland. Elevated CO 2 led to lower leaf-level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30–35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO 2 concentrations also resulted in greater midday photosynthetic rates (70% on average). The effects of CO 2 on stomatal conductance and leaf water potential decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in elevated CO 2, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope discrimination. Increases in CO 2 and photosynthesis resulted in more seeds per plant (30%) and taller and heavier plants (27% and 41%, respectively). Elevated CO 2 also reduced seed N concentrations (9%). 相似文献
20.
We investigated interactions between five species of phloem-feeding aphids (Homoptera: Aphididae) and their host plants at elevated CO 2; Acyrthosiphon pisum (Harris) on Vicia faba L., Aphis nerii Boyer de Fonscolombe on Asclepias syriaca L., Aphis oenotherae Oestlund on Oenothera biennis L., Aulacorthum solani (Kaltenbach) on Nicotiana sylvestris Speg. & Comes and Myzus persicae (Sulzer) on Solanum dulcamara L. Host plants grown at elevated CO 2 generally had greater biomass, leaf area and C:N ratios than those grown at ambient CO 2, while plants with aphids had lower biomass and leaf area than those without aphids.The responses of aphid populations to elevated CO 2 were species-specific with one species increasing ( M. persicae), one decreasing ( A. pisum), and the other three being unaffected. CO 2 treatment did not affect the proportion of alate individuals produced. In general, aphid abundance was not significantly related to foliar nitrogen concentration.We performed separate analyses to test whether either aphid presence or aphid abundance modified the response of host plants to elevated CO 2. In terms of aphid presence, only three of the potential 15 interactions (five aphid species x three plant traits) were significant; A. solani slightly modified the response of the plant biomass to elevated CO 2 and M. persicae affected the response of leaf area and allocation. In terms of aphid abundance, only two of the potential 15 interactions were significant with A. nerii modifying the plant response to CO 2 in terms of total leaf area and allocation.We conclude that, in contrast to other insect groups such as leaf chewers, populations of most phloem-feeders may not be negatively affected by increased CO 2 concentrations in the future. The reasons for this difference include the possibility that aphids may be able to compensate for changes in host plant quality by altering feeding behaviour or by synthesizing amino acids. In addition, there is little evidence that aphid herbivory, even at high levels, will substantially modify the response of plants to elevated CO 2. 相似文献
|