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1.
Elevated CO2 increases seed production more in plant species that form a symbiotic association with N2–fixing bacteria than in species without such association. We studied the mechanism of the increase of seed production with elevated CO2 using nodulated soybean (Glycine max cv. Enrei) and its non-nodulated isogenic line (cv. En1282). Increase in seed production with elevated CO2 was observed in nodulated Enrei but was not in non-nodulated En1282. The increase in seed production in Enrei was explained by the increase in the rate of dry mass production during the reproductive period. This increase was associated with the increase in N assimilation in the reproductive period and the seed N concentration that remained the same as that at ambient CO2. Dry mass production and nitrogen assimilation did not increase in the vegetative phase in both lines. These results accorded with the amount of nodules in Enrei that increased at elevated CO2 especially after flowering. We conclude that the increase in N assimilation in the reproductive period would be the key for increasing soybean yield in the future high-CO2 world.  相似文献   

2.
Elevated CO2 enhances photosynthesis and growth of plants, but the enhancement is strongly influenced by the availability of nitrogen. In this article, we summarise our studies on plant responses to elevated CO2. The photosynthetic capacity of leaves depends not only on leaf nitrogen content but also on nitrogen partitioning within a leaf. In Polygonum cuspidatum, nitrogen partitioning among the photosynthetic components was not influenced by elevated CO2 but changed between seasons. Since the alteration in nitrogen partitioning resulted in different CO2-dependence of photosynthetic rates, enhancement of photosynthesis by elevated CO2 was greater in autumn than in summer. Leaf mass per unit area (LMA) increases in plants grown at elevated CO2. This increase was considered to have resulted from the accumulation of carbohydrates not used for plant growth. With a sensitive analysis of a growth model, however, we suggested that the increase in LMA is advantageous for growth at elevated CO2 by compensating for the reduction in leaf nitrogen concentration per unit mass. Enhancement of reproductive yield by elevated CO2 is often smaller than that expected from vegetative growth. In Xanthium canadense, elevated CO2 did not increase seed production, though the vegetative growth increased by 53%. As nitrogen concentration of seeds remained constant at different CO2 levels, we suggest that the availability of nitrogen limited seed production at elevated CO2 levels. We found that leaf area development of plant canopy was strongly constrained by the availability of nitrogen rather than by CO2. In a rice field cultivated at free-air CO2 enrichment, the leaf area index (LAI) increased with an increase in nitrogen availability but did not change with CO2 elevation. We determined optimal LAI to maximise canopy photosynthesis and demonstrated that enhancement of canopy photosynthesis by elevated CO2 was larger at high than at low nitrogen availability. We also studied competitive asymmetry among individuals in an even-aged, monospecific stand at elevated CO2. Light acquisition (acquired light per unit aboveground mass) and utilisation (photosynthesis per unit acquired light) were calculated for each individual in the stand. Elevated CO2 enhanced photosynthesis and growth of tall dominants, which reduced the light availability for shorter subordinates and consequently increased size inequality in the stand.  相似文献   

3.

Background

If biofuels are to be a viable substitute for fossil fuels, it is essential that they retain their potential to mitigate climate change under future atmospheric conditions. Elevated atmospheric CO2 concentration [CO2] stimulates plant biomass production; however, the beneficial effects of increased production may be offset by higher energy costs in crop management.

Methodology/Main Findings

We maintained full size poplar short rotation coppice (SRC) systems under both current ambient and future elevated [CO2] (550 ppm) and estimated their net energy and greenhouse gas balance. We show that a poplar SRC system is energy efficient and produces more energy than required for coppice management. Even more, elevated [CO2] will increase the net energy production and greenhouse gas balance of a SRC system with 18%. Managing the trees in shorter rotation cycles (i.e., 2 year cycles instead of 3 year cycles) will further enhance the benefits from elevated [CO2] on both the net energy and greenhouse gas balance.

Conclusions/Significance

Adapting coppice management to the future atmospheric [CO2] is necessary to fully benefit from the climate mitigation potential of bio-energy systems. Further, a future increase in potential biomass production due to elevated [CO2] outweighs the increased production costs resulting in a northward extension of the area where SRC is greenhouse gas neutral. Currently, the main part of the European terrestrial carbon sink is found in forest biomass and attributed to harvesting less than the annual growth in wood. Because SRC is intensively managed, with a higher turnover in wood production than conventional forest, northward expansion of SRC is likely to erode the European terrestrial carbon sink.  相似文献   

4.
Williams RS  Lincoln DE  Norby RJ 《Oecologia》2003,137(1):114-122
Predicted increases in atmospheric CO2 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 CO2 enrichment on phytochemicals important for insect success. We investigated the effects of CO2 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 CO2/temperature treatments: (1) ambient temperature, ambient CO2, (2) ambient temperature, elevated CO2 (+300 l l-1 CO2), (3) elevated temperature (+3.5°C), ambient CO2, and (4) elevated temperature, elevated CO2. 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 CO2 treatments in mature leaves, whereas leaves grown at elevated CO2 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 CO2 or temperature treatment. There were no interactive effects of CO2 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 CO2, temperature or their interaction. Our data show that CO2 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 CO2 concentration on leaf constituents.  相似文献   

5.
The direct and indirect effects of increasing levels of atmospheric carbon dioxide (CO2) on plant nitrogen (N) content were studied in a shortgrass steppe ecosystem in northeastern Colorado, USA. Beginning in 1997 nine experimental plots were established: three open-top chambers with ambient CO2 levels (approximately 365 mol mol–1), three open-top chambers with twice-ambient CO2 levels (approximately 720 mol mol–1), and three unchambered control plots. After 3 years of growing-season CO2 treatment, the aboveground N concentration of plants grown under elevated atmospheric CO2 decreased, and the carbon–nitrogen (C:N) ratio increased. At the same time, increased aboveground biomass production under elevated atmospheric CO2 conditions increased the net transfer of N out of the soil of elevated-CO2 plots. Aboveground biomass production after simulated herbivory was also greater under elevated CO2 compared to ambient CO2. Surprisingly, no significant changes in belowground plant tissue N content were detected in response to elevated CO2. Measurements of individual species at peak standing phytomass showed significant effects of CO2 treatment on aboveground plant tissue N concentration and significant differences between species in N concentration, suggesting that changes in species composition under elevated CO2 will contribute to overall changes in nutrient cycling. Changes in plant N content, driven by changes in aboveground plant N concentration, could have important consequences for biogeochemical cycling rates and the long-term productivity of the shortgrass steppe as atmospheric CO2 concentrations increase.  相似文献   

6.

Aims

In view of the projected increase in global air temperature and CO2 concentration, the effects of climatic changes on biomass production, CO2 fluxes and arbuscular mycorrhizal fungi (AMF) colonization in newly established grassland communities were investigated. We hypothesized that above- and below-ground biomass, gross primary productivity (GPP), AMF root colonization and nutrient acquisition would increase in response to the future climate conditions. Furthermore, we expected that increased below-ground C allocation would enhance soil respiration (Rsoil).

Methods

Grassland communities were grown either at ambient temperatures with 375?ppm CO2 (Amb) or at ambient temperatures +3°C with 620?ppm CO2 (T+CO2).

Results

Total biomass production and GPP were stimulated under T+CO2. Above-ground biomass was increased under T+CO2 while belowground biomass was similar under both climates. The significant increase in root colonization intensity under T+CO2, and therefore the better contact between roots and AMF, probably determined the higher above-ground P and N content. Rsoil was not significantly affected by the future climate conditions, only showing a tendency to increase under future climate at the end of the season.

Conclusions

Newly established grasslands benefited from the exposure to elevated CO2 and temperature in terms of total biomass production; higher root AMF colonization may partly provide the nutrients required to sustain this growth response.  相似文献   

7.

Key message

The Amazonian tree Senna reticulata showed an increase in photosynthesis and starch content under elevated [CO 2 ] that led an increment in biomass after 90 days. Elevated [CO 2 ] was also capable of reducing the negative effect of waterlogging.

Abstract

Tree species from the Amazonian floodplains have to cope with low oxygen availability due to annual pulses of inundation that can last up to 7 months. Species capable of adapting to flooding and/or waterlogged conditions usually partition their storage to favor starch and allocate it to roots, where carbohydrates are used to maintain respiration rates during waterlogging. In spite of climate change, virtually nothing is known about how elevated atmospheric CO2 concentration ([CO2]) will affect plants when combined with waterlogging. In this work, we used open top chambers to evaluate the effect of elevated [CO2] during a period of terrestrial phase and in subsequent combination with waterlogged conditions to determine if the surplus carbon provided by elevated [CO2] may improve the waterlogging tolerance of the fast-growing Amazonian legume tree Senna reticulata. During the terrestrial phase, photosynthesis was ca. 28 % higher after 30, 45 and 120 days of elevated [CO2], and starch content in the leaves was, on average, 49 % higher than with ambient [CO2]. Total biomass was inversely correlated to the starch content of leaves, indicating that starch might be the main carbohydrate source for biomass production during the terrestrial phase. This response was more pronounced under elevated [CO2], resulting in 30 % more biomass in comparison to ambient [CO2] plants. After 135 days at elevated [CO2] an inversion has been observed in total biomass accumulation, in which ambient [CO2] presented a greater increment in total biomass in comparison to elevated [CO2], indicating negative effects on growth after long-term CO2 exposure. However, plants with elevated [CO2]/waterlogged displayed a greater increment in biomass in comparison with ambient [CO2]/waterlogged that, unlike during the terrestrial phase, was unrelated to starch reserves. We conclude that S. reticulata displays mechanisms that make this species capable of responding positively to elevated [CO2] during the first pulse of growth. This response capacity is also associated with a “buffering effect” that prevents the plants from decreasing their biomass under waterlogged conditions.  相似文献   

8.

Background and purpose

Rapid increases in atmospheric carbon dioxide concentration ([CO2]) may increase crop residue production and carbon: nitrogen (C:N) ratio. Whether the incorporation of residues produced under elevated [CO2] will limit soil N availability and fertilizer N recovery in the plant is unknown. This study investigated the interaction between crop residue incorporation and elevated [CO2] on the growth, grain yield and the recovery of 15N-labeled fertilizer by wheat (Triticum aestivum L. cv. Yitpi) under controlled environmental conditions.

Methods

Residue for ambient and elevated [CO2] treatments, obtained from wheat grown previously under ambient and elevated [CO2], respectively, was incorporated into two soils (from a cereal-legume rotation and a cereal-fallow rotation) 1 month before the sowing of wheat. At the early vegetative stage 15N-labeled granular urea (10.22 atom%) was applied at 50 kg?N ha?1 and the wheat grown to maturity.

Results

When residue was not incorporated into the soil, elevated [CO2] increased wheat shoot (16 %) and root biomass (41 %), grain yield (19 %), total N uptake (4 %) and grain N removal (8 %). However, the positive [CO2] fertilization effect on these parameters was absent in the soil amended with residue. In the absence of residue, elevated [CO2] increased fertilizer N recovery in the plant (7 %), but when residue was incorporated elevated [CO2] decreased fertilizer N recovery.

Conclusions

A higher fertilizer application rate will be required under future elevated [CO2] atmospheres to replenish the extra N removed in grains from cropping systems if no residue is incorporated, or to facilitate the [CO2] fertilization effect on grain yield by overcoming N immobilization resulting from residue amendment.  相似文献   

9.
Increased concentrations of atmospheric carbon dioxide (CO2) and drought stress have greatly influenced plant growth, the status of nitrogen (N) and phosphorus (P), and N:P ratios. We identified the plant biomass, N and P distributional patterns, and N:P stoichiometry of a grass species on the Loess Plateau in China under elevated CO2 concentration and drought stress conditions. Bothriochloa ischaemum, a C4 perennial herbaceous grass, was grown in pots at CO2 concentrations of 400 (ambient) and 800 (elevated) μmol mol?1 and at 60 ± 5 and 40 ± 5 % of field capacity. The elevated CO2 concentration significantly increased plant total biomass, N concentration, N and P content, allocation of biomass to roots, and allocation of N to shoots, and increased the N:P ratios of whole plants and the shoots, especially under well-watered conditions. Drought stress significantly decreased plant biomass and plant N and P content, especially under elevated CO2. Drought stress decreased the N:P ratios, but was only significant in the roots under ambient CO2. Drought stress may attenuate the stimulation of plant growth and N and P acquisition by CO2 enrichment, and projected elevated CO2 concentrations may partially offset the negative effects of increased drought by increasing the assimilation of N and P.  相似文献   

10.
Elevated atmospheric CO2 concentrations ([CO2]) generally increase primary production of terrestrial ecosystems. Production responses to elevated [CO2] may be particularly large in deserts, but information on their long‐term response is unknown. We evaluated the cumulative effects of elevated [CO2] on primary production at the Nevada Desert FACE (free‐air carbon dioxide enrichment) Facility. Aboveground and belowground perennial plant biomass was harvested in an intact Mojave Desert ecosystem at the end of a 10‐year elevated [CO2] experiment. We measured community standing biomass, biomass allocation, canopy cover, leaf area index (LAI), carbon and nitrogen content, and isotopic composition of plant tissues for five to eight dominant species. We provide the first long‐term results of elevated [CO2] on biomass components of a desert ecosystem and offer information on understudied Mojave Desert species. In contrast to initial expectations, 10 years of elevated [CO2] had no significant effect on standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground components. However, elevated [CO2] increased short‐term responses, including leaf water‐use efficiency (WUE) as measured by carbon isotope discrimination and increased plot‐level LAI. Standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground pools significantly differed among dominant species, but responses to elevated [CO2] did not vary among species, photosynthetic pathway (C3 vs. C4), or growth form (drought‐deciduous shrub vs. evergreen shrub vs. grass). Thus, even though previous and current results occasionally show increased leaf‐level photosynthetic rates, WUE, LAI, and plant growth under elevated [CO2] during the 10‐year experiment, most responses were in wet years and did not lead to sustained increases in community biomass. We presume that the lack of sustained biomass responses to elevated [CO2] is explained by inter‐annual differences in water availability. Therefore, the high frequency of low precipitation years may constrain cumulative biomass responses to elevated [CO2] in desert environments.  相似文献   

11.
Both global change and biological invasions threaten biodiversity worldwide. However, their interactions and related mechanisms are still not well elucidated. To elucidate potential traits contributing to invasiveness and whether ongoing increase in CO2 aggravates invasions, noxious invasive Wedelia trilobata and native Wedelia urticifolia and Wedelia chinensis were compared under ambient and doubled atmospheric CO2 concentrations in terms of growth, biomass allocation, morphology, and physiology. The invader had consistently higher leaf mass fraction (LMF) and specific leaf area than the natives, contributing to a higher leaf area ratio, and therefore to faster growth and invasiveness. The higher LMF of the invader was due to lower root mass fraction and higher fine root percent. On the other hand, the invader allocated a higher fraction of leaf nitrogen (N) to photosynthetic apparatus, which was associated with its higher photosynthetic rate, and resource use efficiency. All these traits collectively contributed to its invasiveness. CO2 enrichment increased growth of all studied species by increasing actual photosynthesis, although it decreased photosynthetic capacities due to decreased leaf and photosynthetic N contents. Responses of the invasive and native plants to elevated CO2 were not significantly different, indicating that the ongoing increase in CO2 may not aggravate biological invasions, inconsistent with the prevailing results in references. Therefore, more comparative studies of related invasive and native plants are needed to elucidate whether CO2 enrichment facilitates invasions.  相似文献   

12.
Noriyuki Osada 《Plant Ecology》2013,214(12):1493-1504
The theory of optimal nitrogen (N) distribution predicts that the carbon gain of plants will be maximised when leaves of higher irradiance have higher N content per area (N area). Most previous studies have examined optimal N distribution without explicitly considering the branching status of plants. I investigated light environment, N distribution and photosynthetic traits of individual leaves of an herbaceous species, Xanthium canadense. X. canadense was grown solitary under high (HN) and low nutrients (LN). Light availability, leaf mass per unit area and N area were measured for all leaves within plants. Daily photosynthesis of the plants of actual N distribution was compared with those of optimal and constant N distribution. Branch production was facilitated in HN but not in LN plants. N area was correlated more with leaf order than with leaf light environment. Although N was more limited and the light environment was less heterogeneous within crowns in LN than in HN plants, leaf N distribution was closer to optimal in the latter. These results suggest that leaf N distribution was not optimised in solitary plants of X. canadense. Because this species often regenerates in a dense stand, leaf N distribution might be selected to maximise carbon gain only in such a stand. Leaf N distribution might thus be constrained by the regeneration strategy of the species.  相似文献   

13.
Dukes  Jeffrey S. 《Plant Ecology》2002,160(2):225-234
The ongoing increase in atmospheric CO2 concentration ([CO2]) is likely to change the species composition of plant communities. To investigate whether growth of a highly invasive plant species, Centaurea solstitialis (yellow starthistle), was affected by elevated [CO2], and whether the success of this species would increase under CO2 enrichment, I grew the species in serpentine soil microcosms, both as a monoculture and as a component of a grassland community. Centaurea grown in monoculture responded strongly to [CO2] enrichment of 350 mol mol–1, increasing aboveground biomass production by 70%, inflorescence production by 74%, and midday photosynthesis by an average of 132%. When grown in competition with common serpentine grassland species, Centaurea responded to CO2 enrichment with similar but nonsignificant increases (+69% aboveground biomass, +71% inflorescence production), while total aboveground biomass of the polyculture increased by 28%. Centaurea's positive CO2 response in monoculture and parallel (but non-significant) response in polyculture provoke questions about possible consequences of increasing CO2 for more typical California grasslands, where the invader already causes major problems.  相似文献   

14.
Increased biomass production in terrestrial ecosystems with elevated atmospheric CO2 may be constrained by nutrient limitations as a result of increased requirement or reduced availability caused by reduced turnover rates of nutrients. To determine the short-term impact of nitrogen (N) fertilization on plant biomass production under elevated CO2, we compared the response of N-fertilized tallgrass prairie at ambient and twice-ambient CO2 levels over a 2-year period. Native tallgrass prairie plots (4.5 m diameter) were exposed continuously (24 h) to ambient and twice-ambient CO2 from 1 April to 26 October. We compared our results to an unfertilized companion experiment on the same research site. Above- and belowground biomass production and leaf area of fertilized plots were greater with elevated than ambient CO2 in both years. The increase in biomass at high CO2 occurred mainly aboveground in 1991, a dry year, and belowground in 1990, a wet year. Nitrogen concentration was lower in plants exposed to elevated CO2, but total standing crop N was greater at high CO2. Increased root biomass under elevated CO2 apparently increased N uptake. The biomass production response to elevated CO2 was much greater on N-fertilized than unfertilized prairie, particularly in the dry year. We conclude that biomass production response to elevated CO2 was suppressed by N limitation in years with below-normal precipitation. Reduced N concentration in above- and belowground biomass could slow microbial degradation of soil organic matter and surface litter, thereby exacerbating N limitation in the long term.  相似文献   

15.
Li  Zhong  Yagi  K.  Sakai  H.  Kobayashi  K. 《Plant and Soil》2004,258(1):81-90
Rice (Oryza sativa) was grown in six sunlit, semi-closed growth chambers for two seasons at 350 L L–1 (ambient) and 650 L L–1 (elevated) CO2 and different levels of nitrogen (N) supplement. The objective of this research was to study the influence of CO2 enrichment and N nutrition on rice plant growth, soil microbial biomass, dissolved organic carbon (DOC) and dissolved CH4. Elevated CO2 concentration ([CO2]) demonstrated a wide range of enhancement to both above- and below-ground plant biomass, in particular to stems and roots (for roots when N was not limiting) in the mid-season (80 days after transplanting) and stems/ears at the final harvest, depending on season and the level of N supplement. Elevated [CO2] significantly increased microbial biomass carbon in the surface 5 cm soil when N (90 kg ha–1) was in sufficient supply. Low N supplement (30 kg ha–1) limited the enhancement of root growth by elevated [CO2], leading consequently to diminished response of soil microbial biomass carbon to CO2 enrichment. The concentration of dissolved CH4 (as well as soil DOC, but to a lesser degree) was observed to be positively related to elevated [CO2], especially at high rate of N application (120 kg ha–1) or at 10 cm depth (versus 5 cm depth) in the later half of the growing season (at 80 kg N ha–1). Root senescence in the late season complicated the assessment of the effect of elevated [CO2] on root growth and soil organic carbon turnover and thus caution should be taken when interpreting respective high CO2 results.  相似文献   

16.

Purpose

This study investigated the residual contribution of legume and fertilizer nitrogen (N) to a subsequent crop under the effect of elevated carbon dioxide concentration ([CO2]).

Methods

Field pea (Pisum sativum L.) was labeled in situ with 15N (by absorption of a 15N-labeled urea solution through cut tendrils) under ambient and elevated (700 μmol mol–1) [CO2] in controlled environment glasshouse chambers. Barley (Hordeum vulgare L.) and its soil were also labeled under the same conditions by addition of 15N-enriched urea to the soil. Wheat (Triticum aestivum L.) was subsequently grown to physiological maturity on the soil containing either 15N-labeled field pea residues (including 15N-labeled rhizodeposits) or 15N-labeled barley plus fertilizer 15N residues.

Results

Elevated [CO2] increased the total biomass of field pea (21 %) and N-fertilized barley (23 %), but did not significantly affect the biomass of unfertilized barley. Elevated [CO2] increased the C:N ratio of residues of field pea (18 %) and N-fertilized barley (19 %), but had no significant effect on that of unfertilized barley. Elevated [CO2] increased total biomass (11 %) and grain yield (40 %) of subsequent wheat crop regardless of rotation type in the first phase. Irrespective of [CO2], the grain yield and total N uptake by wheat following field pea were 24 % and 11 %, respectively, higher than those of the wheat following N-fertilized barley. The residual N contribution from field pea to wheat was 20 % under ambient [CO2], but dropped to 11 % under elevated [CO2], while that from fertilizer did not differ significantly between ambient [CO2] (4 %) and elevated [CO2] (5 %).

Conclusions

The relative value of legume derived N to subsequent cereals may be reduced under elevated [CO2]. However, compared to N fertilizer application, legume incorporation will be more beneficial to grain yield and N supply to subsequent cereals under future (elevated [CO2]) climates.  相似文献   

17.

Key message

The black locust is adapted to elevated [CO 2 ] through changes in nitrogen allocation characteristics in leaves.

Abstract

The black locust (Robinia pseudoacacia L.) is an invasive woody legume within Japan. This prolific species has a high photosynthetic rate and growth rate, and undergoes symbiosis with N2-fixing micro-organisms. To determine the effect of elevated CO2 concentration [CO2] on its photosynthetic characteristics, we studied the chlorophyll (Chl) and leaf nitrogen (N) content, and the leaf structure and N allocation patterns in the leaves and acetylene reduction activity after four growing seasons, in R. pseudoacacia. Our specimens were grown at ambient [CO2] (370 μmol mol?1) and at elevated [CO2] (500 μmol mol?1), using a free air CO2 enrichment (FACE) system. Net photosynthetic rate at growth [CO2] (A growth) and acetylene reduction activity were significantly higher, but maximum carboxylation rate of RuBisCo (V cmax), maximum rate of electron transport driving RUBP regeneration (J max), net photosynthetic rate under enhanced CO2 concentration and light saturation (A max), the N concentration in leaf, and in leaf mass per unit area (LMA) and ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCo) content were significantly lower grown at elevated [CO2] than at ambient [CO2]. We also found that RuBisCo/N were less at elevated [CO2], whereas Chl/N increased significantly. Allocation characteristics from N in leaves to photosynthetic proteins, NL (Light-harvesting complex: LHC, photosystem I and II: PSI and PSII) and other proteins also changed. When R. pseudoacacia was grown at elevated [CO2], the N allocation to RuBisCo (NR) decreased to a greater extent but NL and N remaining increased relative to specimens grown at ambient [CO2]. We suggest that N remobilization from RuBisCo is more efficient than from proteins of electron transport (NE), and from NL. These physiological responses of the black locust are significant as being an adaptation strategy to global environmental changes.
  相似文献   

18.
Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi‐generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO2] and temperature conditions, a full‐factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO2] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO2] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co‐occur.  相似文献   

19.
Over time, the stimulative effect of elevated CO2 on the photosynthesis of rice crops is likely to be reduced with increasing duration of CO2 exposure, but the resultant effects on crop productivity remain unclear. To investigate seasonal changes in the effect of elevated CO2 on the growth of rice (Oryza sativa L.) crops, a free air CO2 enrichment (FACE) experiment was conducted at Shizukuishi, Iwate, Japan in 1998–2000. The target CO2 concentration of the FACE plots was 200 µmol mol?1 above that of ambient. Three levels of nitrogen (N) were supplied: low (LN, 4 g N m?2), medium [MN, 8 (1998) and 9 (1999, 2000) g N m?2] and high N (HN, 12 and 15 g N m?2). For MN and HN but not for LN, elevated CO2 increased tiller number at panicle initiation (PI) but this positive response decreased with crop development. As a result, the response of green leaf area index (GLAI) to elevated CO2 greatly varied with development, showing positive responses during vegetative stages and negative responses after PI. Elevated CO2 decreased leaf N concentration over the season, except during early stage of development. For MN crops, total biomass increased with elevated CO2, but the response declined linearly with development, with average increases of 32, 28, 21, 15 and 12% at tillering, PI, anthesis, mid‐ripening and grain maturity, respectively. This decline is likely to be due to decreases in the positive effects of elevated CO2 on canopy photosynthesis because of reductions in both GLAI and leaf N. Up to PI, LN‐crops tended to have a lower response to elevated CO2 than MN‐ and HN‐crops, though by final harvest the total biomass response was similar for all N levels. For MN‐ and HN‐crops, the positive response of grain yield (ca. 15%) to elevated CO2 was slightly greater than the response of final total biomass while for LN‐crops it was less. We conclude that most of the seasonal changes in crop response to elevated CO2 are directly or indirectly associated with N uptake.  相似文献   

20.
[CO2]- and density-dependent competition between grassland species   总被引:1,自引:1,他引:0  
The predicted ongoing increase of atmospheric carbon dioxide levels is considered to be one of the main threats to biodiversity due to potential changes in biotic interactions. We tested whether effects of intra‐ and interspecific planting density of the calcareous grassland perennials Bromus erectus and Carex flacca change in response to elevated [CO2] (600 ppm) by using factorial combinations of seven densities (0, 1, 2, 4, 8, 16, 24 tillers per 8 × 8 cm2 cell) of both species in plots with and without CO2 enrichment. Although aboveground biomass of C. flacca was increased by 54% under elevated [CO2], the combined aboveground biomass of the whole stand was not significantly increased. C. flacca tended to produce more tillers under elevated [CO2] while B. erectus produced less tillers. The positive effect of [CO2] on the number of tillers of C. flacca was strongest at high intraspecific densities. On the other hand, the negative effect of [CO2] on the number of tillers of B. erectus was not present at intermediate intraspecific planting densities. Seed production of C. flacca was more than doubled under elevated [CO2], while seed production of B. erectus was not affected. Moreover, the mass per seed of C. flacca was increased by elevated [CO2] at intermediate interspecific planting densities while the mass per seed of B. erectus was decreased by elevated [CO2] at high interspecific planting densities. Our results show that the responses of C. flacca and B. erectus to elevated [CO2] depend in a complex way on initial planting densities of both species. In other words, competition between these two model species is both [CO2]‐ and density dependent. On average, however, the effects of [CO2] on the individual species indicate that the composition of calcareous grasslands is likely to change under elevated [CO2] in favor of C. flacca.  相似文献   

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