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1.
Sensitivity to cold and freezing differs between populations within two species of live oaks (Quercus section Virentes Nixon) corresponding to the climates from which they originate. Two populations of Quercus virginiana (originating from North Carolina and north central Florida) and two populations of the sister species, Q. oleoides, (originating from Belize and Costa Rica) were grown under controlled climate regimes simulating tropical and temperate conditions. Three experiments were conducted in order to test for differentiation in cold and freezing tolerance between the two species and between the two populations within each species. In the first experiment, divergences in response to cold were tested for by examining photosystem II (PS II) photosynthetic yield (ΔF/F m′) and non-photochemical quenching (NPQ) of plants in both growing conditions after short-term exposure to three temperatures (6, 15 and 30°C) under moderate light (400 μmol m−2 s−1). Without cold acclimation (tropical treatment), the North Carolina population showed the highest photosynthetic yield in response to chilling temperatures (6°C). Both ecotypes of both species showed maximum ΔF/F m′ and minimum NPQ at their daytime growth temperatures (30°C and 15°C for the tropical and temperate treatments, respectively). Under the temperate treatment where plants were allowed to acclimate to cold, the Q. virginiana populations showed greater NPQ under chilling temperatures than Q. oleoides populations, suggesting enhanced mechanisms of photoprotective energy dissipation in the more temperate species. In the second and third experiments, inter- and intra-specific differentiation in response to freezing was tested for by examining dark-adapted F v/F m before and after overnight freezing cycles. Without cold acclimation, the extent of post-freezing declines in F v/F m were dependent on the minimum freezing temperature (0, −2, −5 or −10°C) for both populations in both species. The most marked declines in F v/F m occurred after freezing at −10°C, measured 24 h after freezing. These declines were continuous and irreversible over the time period. The North Carolina population, however, which represents the northern range limit of Q. virginiana, showed significantly less decline in F v/F m than the north central Florida population, which in turn showed a lower decline in Fv/F m than the two Q. oleoides populations from Belize and Costa Rica. In contrast, after exposure to three months of chilling temperatures (temperate treatment), the two Q. virginiana populations showed no decline in F v/F m after freezing at −10°C, while the two Q. oleoides populations showed declines in F v/F m reaching 0.2 and 0.1 for Costa Rica and Belize, respectively. Under warm growth conditions, the two species showed different F 0 dynamics directly after freezing. The two Q. oleoides populations showed an initial rise in F 0 30 min after freezing, followed by a subsequent decrease, while the Q. virginiana populations showed a continuous decrease in F 0 after freezing. The North Carolina population of Q. virginiana showed a tendency toward deciduousness in response to winter temperatures, dropping 58% of its leaves over the three month winter period compared to only 6% in the tropical treatment. In contrast, the Florida population dropped 38% of its leaves during winter. The two populations of the tropical Q. oleoides showed no change in leaf drop during the 3-months winter (10% and 12%) relative to their leaf drop over the same timecourse in the tropical treatment. These results indicate important ecotypic differences in sensitivity to freezing and cold stress between the two populations of Q. virginiana as well as between the two species, corresponding to their climates of origin.  相似文献   

2.
Li  X.-G.  Meng  Q.-W.  Jiang  G.-Q.  Zou  Q. 《Photosynthetica》2003,41(2):259-265
The photoprotection of energy dissipation and water-water cycle were investigated by comparing chilling sensitivity of photosystems 2 (PS2) and 1 (PS1) in two chilling-sensitive plants, cucumber and sweet pepper, upon exposure to 4 °C under low irradiance (100 μmol m−2 s−1) for 6 h. During chilling stress, the maximum photochemical efficiency of PS2 (Fv/Fm) decreased only slightly in both plants, but the oxidisable P700 decreased markedly, which indicated that PS1 was more sensitive to chilling treatment under low irradiance than PS2. Sweet pepper leaves had lower Fv/Fm, higher non-photochemical quenching (NPQ), and higher oxidisable P700 during chilling stress. Activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in cucumber leaves was higher, but APX activity decreased apparently compared to that at room temperature. The productions of active oxygen species (H2O2, O2 ) increased in both plants, faster in cucumber leaves than in sweet pepper leaves. In sweet pepper leaves, a stronger de-epoxidation of the xanthophyll cycle pigments, a higher NPQ could act as a major protective mechanism to reduce the formation of active oxygen species during stress. Thus sensitivity of both plants to chilling under low irradiance was dominated by the protective mechanisms between PS1 and PS2, especially the energy dissipation and the water-water cycle. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
Seeds of Suaeda salsa were cultured in dark for 3 d and betacyanin accumulation in seedlings was promoted significantly. Then the seedlings with accumulated betacyanin (C+B) were transferred to 14/10 h light/dark and used for chilling treatment 15 d later. Photosystem 2 (PS2) photochemistry, D1 protein content, and xanthophyll cycle during the chilling-induced photoinhibition (exposed to 5 °C at a moderate photon flux density of 500 μmol m−2 s−1 for 3 h) and the subsequent restoration were compared between the C+B seedlings and the control (C) ones. The maximal efficiency of PS2 photochemistry (Fv/Fm), the efficiency of excitation energy capture by open PS2 centres (Fv′/Fm′), and the yield of PS2 electron transport (ΦPS2) of the C+B and C leaves both decreased during photoinhibition. However, smaller decreases in Fv/Fm, Fv′/Fm′, and ΦPS2 were observed in the C+B leaves than in C ones. At the same time, the deepoxidation state of xanthophyll cycle, indicated by (A+Z)/(V+A+Z) ratio, increased rapidly but the D1 protein content decreased considerably during the photoinhibition. The increase in rate of (A+Z)/(V+A+Z) was higher but the D1 protein turnover was slower in C+B than C leaves. After photoinhibition treatment, the plants were transferred to a dim irradiation (10 μmol m−2 s−1) at 25 °C for restoration. During restoration, the chlorophyll (Chl) fluorescence parameters, D1 protein content, and xanthophyll cycle components relaxed gradually, but the rate and level of restoration in the C+B leaves was greater than those in the C leaves. The addition of betacyanins to the thylakoid solution in vitro resulted in similar changes of Fv/Fm, D1 protein content, and (A+Z)/(V+A+Z) ratio during the chilling process. Therefore, betacyanin accumulation in S. salsa seedlings may result in higher resistance to photoinhibition, larger slowing down of D1 protein turnover, and enhancement of non-radiative energy dissipation associated with xanthophyll cycle, as well as in greater restoration after photoinhibition than in the control when subjected to chilling at moderate irradiance.  相似文献   

4.
In order to better elucidate fixed-C partitioning, nutrient acquisition and water relations of prairie grasses under elevated [CO2], we grew the C4 grass Bouteloua gracilis (H.B.K.) lag ex Steud. from seed in soil-packed, column-lysimeters in two growth chambers maintained at current ambient [CO2] (350 μL L−1) and twice enriched [CO2] (700 μL L−1). Once established, plants were deficit irrigated; growth chamber conditions were maintained at day/night temperatures of 25/16°C, relative humidities of 35%/90% and a 14-hour photoperiod to simulate summer conditions on the shortgrass steppe in eastern Colorado. After 11 weeks of growth, plants grown under CO2 enrichment had produced 35% and 65% greater total and root biomass, respectively, and had twice the level of vesicular-arbuscular mycorrhizal (VAM) infection (19.8% versus 10.8%) as plants grown under current ambient [CO2]. The CO2-enriched plants also exhibited greater leaf water potentials and higher plant water use efficiencies. Plant N uptake was reduced by CO2 enrichment, while P uptake appeared little influenced by CO2 regime. Under the conditions of the experiment, CO2 enrichment increased root biomass and VAM infection via stimulated growth and adjustments in C partitioning below-ground. The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.  相似文献   

5.
Kurasová  I.  Kalina  J.  Štroch  M.  Urban  O.  Špunda  V. 《Photosynthetica》2003,41(2):209-219
The response of barley (Hordeum vulgare L. cv. Akcent) to various photosynthetic photon flux densities (PPFDs) and elevated [CO2] [700 μmol (CO2) mol−1; EC] was studied by gas exchange, chlorophyll (Chl) a fluorescence, and pigment analysis. In comparison with barley grown under ambient [CO2] [350 μmol (CO2) mol−1; AC] the EC acclimation resulted in a decrease in photosynthetic capacity, reduced stomatal conductance, and decreased total Chl content. The extent of acclimation depression of photosynthesis, the most pronounced for the plants grown at 730 μmol m−2 s−1 (PPFD730), may be related to the degree of sink-limitation. The increased non-radiative dissipation of absorbed photon energy for all EC plants corresponded to the higher de-epoxidation state of xanthophylls only for PPFD730 barley. Further, a pronounced decrease in photosystem 2 (PS2) photochemical efficiency (given as FV/FM) for EC plants grown at 730 and 1 200 μmol m−2 s−1 in comparison with AC barley was related to the reduced epoxidation of antheraxanthin and zeaxanthin back to violaxanthin in darkness. Thus the EC conditions sensitise the photosynthetic apparatus of high-irradiance acclimated barley plants (particularly PPFD730) to the photoinactivation of PS2. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

6.
We studied changes in biochemical and physiological status, level of oxidative damage, and antioxidant enzyme activities in detached leaves of cucumber plants (Cucumis sativus L. cv. Pyunggangnaebyungsamchuk) that were exposed to a low temperature (4°C). Chlorophyll fluorescence (Fv/Fm) declined during the chilling treatment, but was slowly restored after the tissues were returned to 25°C. Likewise, the fluorescence quenching coefficient and relative water content decreased during the stress period, but then increased during recovery. In contrast, we detected a significant rise in protein and hydrogen peroxide contents in the chilled leaves, as well as higher activities for superoxide dismutase, ascorbate peroxidase, peroxidase, and glutathione reductase. However, the level of catalase decreased not only during chilling but also after 24 h of recovery. These results indicate that exposure to low temperatures acts as an oxidative stress. Moreover, we propose that a regulating mechanism exists in the detached cucumber leaves and contains an antioxidant defense system that induces active oxygen species, thereby alleviating the effects of chilling stress within 12 h.  相似文献   

7.
Seasonal changes in foliage nitrogen (N) and carbon (C) concentrations and δ15N and δ13C ratios were monitored during a year in Erica arborea, Myrtus communis and Juniperus communis co-occurring at a natural CO2 spring (elevated [CO2], about 700 μmol mol−1) and at a nearby control site (ambient [CO2], 360 μmol mol−1) in a Mediterranean environment. Leaf N concentration was lower in elevated [CO2] than in ambient [CO2] for M. communis, higher for J. communis, and dependent on the season for E. arborea. Leaf C concentration was negatively affected by atmospheric CO2 enrichment, regardless of the species. C/N ratio varied concomitantly to N. Leaves in elevated [CO2] showed lower δ13C, and therefore likely lower water use efficiencies than leaves at the control site, regardless of the species, suggesting substantial photosynthetic acclimation under long-term CO2-enriched atmosphere. Leaves of E. arborea showed lower values of δ15N under elevated [CO2], but this was not the case of M. communis and J. communis foliage. The use of the resources and leaf chemical composition are affected by elevated [CO2], but such an effect varies during the year, and is species-dependent. The seasonal dependency and species specificity suggest that plants are able to exploit different available water and N resources within Mediterranean sites. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
This paper aims to determine the changes in reactive oxygen species (ROS) and the responses of the lily (Lilium longiflorum L.) antioxidant system to short-term high temperatures. Plants were exposed to three levels of heat stress (37°C, 42°C, 47°C) for 10 h when hydrogen peroxide (H2O2) and superoxide (O2) production rate along with membrane injury indexes, and changes in antioxidants were measured. Compared with the control (20°C), electrolyte leakage and MDA concentration varied slightly after 10 h at 37°C and 42°C, while increased significantly at 47°C. During 10 h at 37°C and 42°C, antioxidant enzyme activities, such as SOD, POD, CAT, APX and GR, were stimulated and antioxidants (AsA and GSH concentrations) maintained high levels, which resulted in low levels of O2 and H2O2 concentration. However, after 10 h at 47°C, SOD, APX, GR activities and GSH concentration were similar to the controls, while POD, CAT activities and AsA concentration decreased significantly as compared with the control, concomitant with significant increase in O2 and H2O2 concentrations. In addition, such heat-induced effects on antioxidant enzymes were also confirmed by SOD and POD isoform, as Cu/ZnSOD maintained high stability under heat stress and the intensity of POD isoforms reduced with the duration of heat stress, especially at 47°C. It is concluded that in lily plants, the oxidative damage induced by heat stress was related to the changes in antioxidant enzyme activities and antioxidants.  相似文献   

9.
The effects of chilling at 14 and 7°C on plant growth, CO2 assimilation, light allocation, photosynthetic electron flux and antioxidant metabolism were examined in cucumber (Cucumis sativus L. cv. Jinyan No. 4, CS) plants with figleaf gourd (Cucurbita ficifolia Bouché, CF) and cucumber as rootstocks, respectively. Growth inhibition by chilling at 7°C was characterized by irreversible inhibition of CO2 assimilation in grafted plants with cucumber as rootstock and scion (CS/CS) but this effect was significantly alleviated by grafting onto CF roots (CS/CF). Chilled CS/CF plants exhibited a higher photosynthetic activity and lower proportion of energy dissipation than chilled CS/CS plants. Chilling resulted in a greater decrease in the electron flux in photosystem (PS) II (J PSII) than the rate of energy dissipation either via light-dependent (J NPQ) or via constitutive thermal dissipation and fluorescence (J f,D) in CS/CS plants. In parallel with the reduction in J PSII, electron flux to oxygenation (J o) and carboxylation by Rubisco (J c) all decreased significantly whilst alternative electron flux in PS II (J a) increased, especially in CS/CS plants. Moreover, CS/CF plants exhibited higher activity of antioxidant enzymes, lower antioxidant content and less membrane peroxidation relative to CS/CS plants after chilling.  相似文献   

10.
The interaction of extreme temperature events with future atmospheric CO2 concentrations may have strong impacts on physiological performance of desert shrub seedlings, which during the critical establishment phase often endure temperature extremes in conjunction with pronounced drought. To evaluate the interaction of drought and CO2 on photosynthesis during heat stress, one-year-old Larrea tridentata[DC] Cov. seedlings were exposed to nine days of heat with midday air temperature maxima reaching 53 °C under three atmospheric CO2 concentrations (360, 550 and 700 mol mol–1) and two water regimes (well-watered and droughted). Photosynthetic gas exchange, chlorophyll fluorescence and water potential responses were measured prior to, during and one week following the high temperature stress event. Heat stress markedly decreased net photosynthetic rate (A net), stomatal conductance (g s), and the photochemical efficiency of photosystem II (F v/F m) in all plants except for well-watered L. tridentata grown in 700 mol mol–1 CO2. A net and g s remained similar to pre-stress levels in these plants. In droughted L. tridentata, A net was ca. 2× (in 550 mol mol–1 CO2) to 3× (in 700 mol mol–1 CO2) higher than in ambient-CO2-grown plants, while g s and F v/F m were similar and low in all CO2 treatments. Following heat stress, g s in all well-watered plants rose dramatically, exceeding pre-stress levels by up to 100%. In droughted plants, g s and A net rose only in plants grown at elevated CO2 following release from heat. This recovery response was strongest at 700 mol mol–1 CO2, which returned to A net and g s values similar to pre-heat following several days of recovery. Extreme heat diminished the photosynthetic down-regulation response to growth at elevated CO2 under well-watered conditions, similar to the action of drought. Ambient-CO2-grown L. tridentata did not show significant recovery of photosynthetic capacity (A \max and CE) after alleviation of temperature stress, especially when exposed to drought, while plants exposed to elevated CO2 appeared to be unaffected. These findings suggest that elevated CO2 could promote photosynthetic activity during critical periods of seedling establishment, and enhance the potential for L. tridentata to survive extreme high temperature events.  相似文献   

11.
In our previous study, it was found that abscisic acid (ABA) improved the chilling resistance of Stylosanthes guianensis. In order to determine the effects of ABA on photosynthesis and photochemistry of S. guianensis, an experiment was conducted under controlled condition to determine the effects of exogenous ABA on stomatal conductance (gs), transpiration (E), photosynthetic rate (A) and chlorophyll a fluorescence of this pasture legume. The results showed that ABA treatment reduced A, gs, and E under both chilling (8 °C) and control temperature (28 °C). A of the ABA treated plants returned to a high rate, while that of the water-treated plants remained low when plants were rewarmed after chilling treatment. ABA-treated plants had higher maximum photochemical efficiency (Fv/Fm), non-photochemical quenching (NPQ), quantum efficiency of PS II photochemistry (Φps ii) than water-treated ones during chilling. Although the biomass of S. guianensis was reduced by ABA under control temperature, ABA-treated plants had higher biomass than water-treated ones after 7 days of recovery.  相似文献   

12.
Simultaneous measurements of chlorophyll (Chl) fluorescence and CO2 assimilation (A) in Vicia faba leaves were taken during the first weeks of growth to evaluate the protective effect of 24-epibrassinolide (EBR) against damage caused by the application of the herbicide terbutryn (Terb) at pre-emergence. V. faba seeds were incubated for 24 h in EBR solutions (2 × 10−6 or 2 × 10−5 mM) and immediately sown. Terb was applied at recommended doses (1.47 or 1.96 kg ha−1) at pre-emergence. The highest dose of Terb strongly decreased CO2 assimilation, the maximum quantum yield of PSII photochemistry in the dark-adapted state (F V/F M), the nonphotochemical quenching (NPQ), and the effective quantum yield (ΔF/FM) during the first 3–4 weeks after plant emergence. Moreover, Terb increased the basal quantum yield of nonphotochemical processes (F 0/F M), the degree of reaction center closure (1 − q p), and the fraction of light absorbed in PSII antennae that was dissipated via thermal energy dissipation in the antennae (1 − FV/FM). The herbicide also significantly reduced plant growth at the end of the experiment as well as plant length, dry weight, and number of leaves. The application of EBR to V. faba seeds before sowing strongly diminished the effect of Terb on fluorescence parameters and CO2 assimilation, which recovered 13 days after plant emergence and showed values similar to those of control plants. The protective effect of EBR on CO2 assimilation was detected at a photosynthetic photon flux density (PFD) of 650 μmol m−2 s−1 and the effect on ΔF/FM and photosynthetic electron transport (J) was detected under actinic lightings up to 1750 μmol m−2 s−1. The highest dose of EBR also counteracted the decrease in plant growth caused by Terb, and plants registered the same growth values as controls.  相似文献   

13.
This study examined the effects of season-long exposure of Chinese pine (Pinus tabulaeformis) to elevated carbon dioxide (CO2) and/or ozone (O3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in open-top chambers (OTC) were exposed to control (ambient O3, 55 nmol mol−1 + ambient CO2, 350 μmol mol−1, CK), elevated CO2 (ambient O3 + high CO2, 700 μmol mol−1, EC) and elevated O3 (high O3, 80 ± 8 nmol mol−1 + ambient CO2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth in elevated O3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity were observed in trees exposed to elevated CO2 concentration compared with control. Elevated O3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees pre-exposed to elevated CO2 were transferred to elevated O3 (EC–EO) or trees pre-exposed to elevated O3 were transferred to elevated CO2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may cause changes in Chinese pine’s growth. An erratum to this article can be found at  相似文献   

14.
The heat tolerance of 8 temperate- and 1 subtropical-origin C3 species as well as 17 tropical-origin ones, including C3, C4, and CAM species, was estimated using both F0-T curve and the ratio of chlorophyll fluorescence parameters, prior to and after high temperature treatment. When leaves were heated at the rate of ca. 1 °C min−1 in darkness, the critical temperature (Tc) varied extensively among species. The Tc's of all 8 temperate-origin species ranged between 40–46 °C in winter (mean temperature 16–19 °C), and between 32–48 °C in summer (mean temperature ca. 30 °C). Those for 1 subtropical- and 12 tropical-origin C3 species ranged between 25–44 °C and 35–48 °C, and for 1 CAM and 4 C4 species were 41–47 and 45–46 °C, respectively. Acclimating three C3 herbaceous plants at high temperature (33/28 °C, day/night) for 10 d in winter caused their Tc's rising to nearly the values measured in summer. When leaves were exposed to 45 °C for 20 min and then kept at room temperature in darkness for 1 h, a significant correlation between RFv/m (the ratio of Fv/Fm before and after 45 °C treatment) and Tc was observed for all tested temperate-origin C3 species as well as tropical-origin CAM and C4 species. However, F0 and Fv/Fm of the tropical-origin C3 species were less sensitive to 45 °C treatment, regardless of a large variation of Tc; thus no significant correlation was found between their RFv/m and Tc. Thus Tc might not be a suitable index of heat tolerance for plants with wide range of environmental adaptation. Nevertheless, Tc's of tropical origin C3 species, varying and showing high plasticity to seasonal changes and temperature treatment, appeared suitable for the estimation of the degree of temperature acclimation in the same species.  相似文献   

15.
Gorissen  A.  Cotrufo  M.F. 《Plant and Soil》2000,224(1):75-84
Leaf and root tissue of Lolium perenne L., Agrostis capillaris L. and Festuca ovina L. grown under ambient (350 μl l-1 CO2) and elevated (700 μl l-1) CO2 in a continuously 14C-labelled atmosphere and at two soil N levels, were incubated at 14°C for 222 days. Decomposition of leaf and root tissue grown in the low N treatment was not affected by elevated [CO2], whereas decomposition in the high N treatment was significantly reduced by 7% after 222 days. Despite the increased C/N ratio (g g-1) of tissue cultivated at elevated [CO2] when compared with the corresponding ambient tissue, there was no significant correlation between initial C/N ratio and 14C respired. This finding suggests that the CO2-induced changes in decomposition rates do not occur via CO2-induced changes in C/N ratios of plant materials. We combined the decomposition data with data on 14C uptake and allocation for the same plants, and give evidence that elevated [CO2] has the potential to increase soil C stores in grassland via increasing C uptake and shifting C allocation towards the roots, with an inherent slower decomposition rate than the leaves. An overall increase of 15% in 14C remaining after 222 days was estimated for the combined tissues, i.e., the whole plants; the leaves made a much smaller contribution to the C remaining (+6%) than the roots (+26%). This shows the importance of clarifying the contribution of roots and leaves with respect to the question whether grassland soils act as a sink or source for atmospheric CO2. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

16.
Stinson KA  Bazzaz FA 《Oecologia》2006,147(1):155-163
Plants growing in dense stands may not equally acquire or utilize extra carbon gained in elevated CO2. As a result, reproductive differences between dominant and subordinate plants may be altered under rising CO2 conditions. We hypothesized that elevated CO2 would enhance the reproductive allocation of shaded, subordinate Ambrosia artemisiifolia L. (Asteraceae) individuals more than that of light-saturated dominants. We grew stands of A. artemisiifolia at either 360 or 720 μL L−1 CO2 levels and measured the growth and reproductive responses of competing individuals. To test whether elevated CO2 altered size and reproductive inequalities within stands, we compared stand-level coefficients of variation (CV) in height growth and final shoot, root, and reproductive organ biomasses. Elevated CO2 enhanced biomass and reduced the CV for all aspects of plant growth, especially reproductive biomass. Allocation to reproduction was higher in the elevated CO2 than in the ambient treatment, and this difference was more pronounced in small, rather than large plant positive relationships between the CV and total stand productivity declined under elevated CO2, indicating that growth enhancements to smaller plants diminished the relative biomass advantages of larger plants in increasingly crowded conditions. We conclude that elevated CO2 stimulates stand-level reproduction while CO2-induced growth gains of subordinate A. artemisiifolia plants minimize differences in the reproductive output of small and large plants. Thus, more individuals are likely to produce greater amounts of seeds and pollen in future populations of this allergenic weed.  相似文献   

17.
In order to predict the potential impacts of global change, it is important to understand the impact of increasing global atmospheric [CO2] on the growth and yield of crop plants. The objectives of this study were to determine the interaction of N fertilization rates and atmospheric [CO2] on radiation interception and radiation-use efficiency of rice (Oryza sativa L. cv. IR72) grown under tropical field conditions. Rice plants were grown inside open top chambers in a lowland rice field at the International Rice Research Institute in the Philippines at ambient (about 350 μmol mol-1) or elevated (about 600 μmol mol-1 during the 1993 wet season and 700 μmol mol-1 during the 1994 dry season) in combination with three levels of applied N (0, 50 or 100 kg N ha-1 in the wet season; 0, 90 or 200 kg N ha-1 in the dry season). Light interception was not directly affected by [CO2], but elevated [CO2] indirectly increased light interception through increasing total absorbed N. Plant N requirement for radiation interception was similar for rice grown under ambient [CO2] or elevated [CO2] treatments. The conversion efficiency of intercepted radiation to dry matter, radiation-use efficiency (RUE), was about 35% greater at elevated [CO2] than at ambient [CO2]. The relationship between leaf N and RUE was curvilinear. At ambient [CO2], RUE was fairly stable across levels of leaf N, but leaf N less than about 2.5% resulted in lower RUE for plants grown with elevated [CO2] than for plant grown at ambient [CO2]. Decreased leaf N with increased [CO2], therefore decreased RUE of rice plants grown at elevated [CO2]. When predicting responses of rice to elevated [CO2], RUE should be adjusted with a decrease in leaf N. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

18.
One-year-old oak (Quercus mongolica Fisch.) seedlings were grown in growth chambers for 30 days to investigate the effects of the combination of elevated CO2 concentration ([CO2], 700 μmol/mol) and temperature (ambient T + 4°C) and only elevated temperature (ambient T +4°C) on leaf gas exchange, chlorophyll a fluorescence, and chlorophyll content. In the growth chambers, natural conditions of the Maoershan mountain regions of Heilongjiang Province (45–46°N, 127–128°E) of China for the average growth season were simulated. The results showed that the maximum net photosynthetic rate (P Nmax) was ≈ 1.64 times greater at elevated temperature than at ambient temperature. The irradiance saturation point (I s), apparent quantum yield (AQY), maximum photosystem II efficiency (F v/F m), and chlorophyll content significantly increased, while irradiance compensation point (I c) was not affected by elevated temperature. The combination of elevated [CO2] and temperature also significantly increased P Nmax by approximately 34% but much lower than that under elevated temperature only. In the case of factor combination, dark respiration (R d), I c, F v/F m, and total chlorophyll content increased significantly, while I s and AQY were not affected. Moreover, under elevated [CO2] and temperature, R d and I c, F v/F m were significantly higher than under elevated temperature only. The results indicated that the combination of elevated [CO2] and temperature expected in connection with the further global climate change may affect carbon storage of the coenotype of Q. mongolica in this region of China. This text was submitted by the authors in English.  相似文献   

19.
Microalgae perform oxygenic photosynthesis and are capable of taking up a large amount of CO2, using an inducible CO2 concentrating mechanism (CCM), and fixing CO2 into higher compounds. These characteristics make the microalgae potentially useful for removal and utilization of CO2 emitted from industrial plants and, generally, the usage of photosynthetic microorganisms has increased and significantly improved as a solution for CO2 emissions. In this light and based on previous research using Anabaena cylindrica IAM M1 and Spirulina platensis IAM M 135, enhancement was sought for CO2 fixation and biomass production by Chlorella vulgaris Buitenzorg by increasing the photon flux density concurrent with increases in culture biomass during the cellular growth phase and was compared to cultures of Chlorella grown at optimal constant illumination, with all cultures grown using Bennick basal medium, 29°C, and a flow of 1.0 atm. 10% CO2 enriched air delivered to three in serial photobioreactors of 0.200 dm3 capacity each. The results showed that increasing illumination during culture increased biomass production of Chlorella by ∼60% as well as increased CO2 fixation ability by ∼7.0%. It was also demonstrated that the non-competitive inhibition of [HCO3 ] as a carbon source significantly affected the cultivation in both the increasing and constant photon flux density regimes.  相似文献   

20.
Summary CO2 efflux from tussock tundra in Alaska that had been exposed to elevated CO2 for 2.5 growing seasons was measured to assess the effect of long- and short-term CO2 enrichment on soil respiration. Long-term treatments were: 348, 514, and 683 μll−1 CO2 and 680 μll−1 CO2+4°C above ambient. Measurements were made at 5 CO2 concentrations between 87 and 680 μll−1 CO2. Neither long- or short-term CO2 enrichment significantly affected soil CO2 efflux. Tundra developed at elevated temperature and 680 μll−1 CO2 had slightly higher, but not statistically different, mean respiration rates compared to untreated tundra and to tundra under CO2 control alone.  相似文献   

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