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1.
Summary We examined how different wind speeds and interactions between plant age and wind affect growth and biomass allocation of Sinapis alba L. (white mustard). Physiological and growth measurements were made on individuals of white mustard grown in controlled-environment wind tunnels at windspeeds of 0.3, 2.2 and 6.0 ms–1 for 42 days. Plants were harvested at four different dates. Increasing wind speed slightly increased transpiration and stomatal conductance. We did not observe a significant decline in the photosynthetic rate per unit of leaf area. Number of leaves, stem length, leaf area and dry weights of total biomass and plant parts were significantly lower in plants exposed at high wind speed conditions. There were no significant differences in the unit leaf rate nor relative growth rates, although these were always lower in plants grown at high wind speed. Allocation and architectural parameters were also examined. After 42 days of exposure to wind, plants showed higher leaf area ratio, root and leaf weight ratios and root/shoot ratio than those grown at control treatment. Only specific leaf area declined significantly with wind speed, but stem and reproductive parts also decreased. The responses of plants to each wind speed treatment depended on the age of the plant for most of the variables. It is suggested that wind operates in logarithmic manner, with relatively small or no effect at lower wind speeds and a much greater effect at higher speeds. Since there is no evidence of a significant reduction in photosynthetic rate of Sinapis with increasing wind speed it is suggested that the effect of wind on plant growth was due to mechanical effects leading to changes in allocation and developmental patterns. 相似文献
2.
The influence of plant density on the responses of Sinapis alba to CO2 and windspeed 总被引:1,自引:0,他引:1
Plants in nature live in populations of variable density, a characteristic which may influence individual plant responses to the environment. We investigated how the responses of Sinapis alba plants to different wind speeds and CO2 concentrations could be modified by plant density. In our wind-density experiment the expectation that mechanical and physiological effects of wind will be ameliorated by growing in high density, as a result of positive plant interactions, was realised. Although individual plants were smaller at higher densities, the effect of increasing windspeed was much less than at lower plant densities. A similar reduced sensitivity of individual plant growth under high densities was also observed under CO2 enrichment. When measured as a population or stand response, there was no effect of density on the CO2 responses, with all stands showing very similar increases in total biomass with CO2 enrichment. In the wind speed experiment, total biomass per stand increased significantly with density, although there was no effect of density on the wind speed response. Specific leaf area decreased with increasing wind speed and this response was significantly affected by the density at which the plants grew. 相似文献
3.
Increases in the concentration of atmospheric carbon dioxide may have a fertilizing effect on plant growth by increasing photosynthetic rates and therefore may offset potential growth decreases caused by the stress associated with higher temperatures and lower precipitation. However, plant growth is determined both by rates of net photosynthesis and by proportional allocation of fixed carbon to autotrophic tissue and heterotrophic tissue. Although CO2 fertilization may enhance growth by increasing leaf-level assimilation rates, reallocation of biomass from leaves to stems and roots in response to higher concentrations of CO2 and higher temperatures may reduce whole-plant assimilation and offset photosynthetic gains. We measured growth parameters, photosynthesis, respiration, and biomass allocation of Pinus ponderosa seedlings grown for 2 months in 2×2 factorial treatments of 350 or 650 bar CO2 and 10/25° C or 15/30° C night/day temperatures. After 1 month in treatment conditions, total seedling biomass was higher in elevated CO2, and temperature significantly enhanced the positive CO2 effect. However, after 2 months the effect of CO2 on total biomass decreased and relative growth rates did not differ among CO2 and temperature treatments over the 2-month growth period even though photosynthetic rates increased 7% in high CO2 treatments and decreased 10% in high temperature treatments. Additionally, CO2 enhancement decreased root respiration and high temperatures increased shoot respiration. Based on CO2 exchange rates, CO2 fertilization should have increased relative growth rates (RGR) and high temperatures should have decreased RGR. Higher photosynthetic rates caused by CO2 fertilization appear to have been mitigated during the second month of exposure to treatment conditions by a 3% decrease in allocation of biomass to leaves and a 9% increase in root:shoot ratio. It was not clear why diminished photosynthetic rates and increased respiration rates at high temperatures did not result in lower RGR. Significant diametrical and potentially compensatory responses of CO2 exchange and biomass allocation and the lack of differences in RGR of ponderosa pine after 2 months of exposure of high CO2 indicate that the effects of CO2 fertilization and temperature on whole-plant growth are determined by complex shifts in biomass allocation and gas exchange that may, for some species, maintain constant growth rates as climate and atmospheric CO2 concentrations change. These complex responses must be considered together to predict plant growth reactions to global atmospheric change, and the potential of forest ecosystems to sequester larger amounts of carbon in the future. 相似文献
4.
Sitka spruce [Picea sitchensis (Bong.) Carr.] seedlings were grown for 3 years in an outside control plot or in ambient (355 mol mol-1) or elevated (ambient + 350 mol mol-1) atmospheric CO2 environments, within open top chambers (OTCs) at the Institute of Terrestrial Ecology, Edinburgh. Sequential harvests were carried out at the end of each growing season and throughout the 1991 growing season, five in all. Plants grown in elevated CO2 had, (i) 35 and 10% larger root/shoot ratios at the end of the first and third season, respectively, (ii) significantly higher summer leader extension relative growth rates, which declined more rapidly in early autumn than ambient grown plants, (iii) after three growing seasons a significantly increased mean annual relative growth rate, (iv) consistently lower foliar nutrient concentrations, and (v) after two growing seasons smaller total projected needle areas. Plants grown inside OTCs were taller, heavier and had a smaller root/shoot ratio than those grown outside the chambers. There was no effect of CO2 concentration on Sitka spruce leaf characteristics, although leaf area ratio, specific leaf area and leaf weight ratio all fell throughout the course of the 3 year experiment. 相似文献
5.
J. Franzaring S. WellerI. Schmid A. Fangmeier 《Environmental and Experimental Botany》2011,72(2):284-296
Atmospheric CO2 enrichment is expected to affect the resource use efficiency of C3 plants with respect to water, nutrients and light in an interactive manner. The responses of oilseed rape (OSR) to elevated CO2 have not much been addressed. Since the crop has low nitrogen use efficiency, the interactive effects of CO2 enrichment and nitrogen supply deserve particular attention.Spring OSR was grown in climate chambers simulating the seasonal increments of day length and temperature in South-Western Germany. Three levels of N fertilisation representing 75, 150 and 225 kg ha−1 and two CO2 concentrations (380 and 550 μmol mol−1) were used to investigate changes in source-sink relationships, plant development and senescence, water use efficiency of the dry matter production (WUEprod.), allocation patterns to different fractions, growth, yield and seed oil contents. Seven harvests were performed between 72 and 142 days after sowing (DAS).Overall, plant performance in the chambers was comparable to the development under field conditions. While CO2 responses were small in the plants receiving lowest N-levels, several significant N × CO2 interactions were observed in the other treatments. Increasing the N availability resulted in longer flowering windows, which were furthermore extended at elevated CO2 concentrations. Nevertheless, significantly less biomass was allocated to reproductive structures under elevated CO2, while the vegetative C-storing organs continued to grow. At the final harvest shoot mass of the CO2 exposed plants had increased by 9, 8 and 15% in the low, medium and high N treatments. Root growth was increased even more by 17, 43 and 33%, respectively and WUEprod. increased by 23, 42 and 35%. At the same time, seed oil contents were significantly reduced by CO2 enrichment in the treatments with ample N supply.Obviously, under high N-supply, the CO2 fertilisation induced exaggerated growth of vegetative tissues at the expense of reproductive structures. The interruption of source-sink relationships stimulated the formation of side shoots and flowers (branching out). While direct effects of elevated CO2 on flowering can be excluded, we assume that the increased growth under high N and CO2 supply created nutrient imbalances which hence affected flowering and seed set.Nevertheless, the final seed macronutrient concentrations were slightly increased by elevated CO2, indicating that remobilisation of nutrients from the sources (leaves) to the sinks (seeds) remained effective. These findings were supported by the lower nitrogen concentrations in senescing leaves and probably increased N remobilisation to other plant parts under elevated concentrations of CO2. All the same, CO2 enrichment caused a decline in seed oil contents, which may translate into a reduced crop quality. 相似文献
6.
The influence of inefeased atmospheric CO2 on the interaction between plant growth and water use is proving to be one of the most profound impacts of the anthropogenic Greenhouse Effect. This paper illustrates the interaction between CO2 and water in plant growth at a range of scales. Most published work has concentrated on water use efficiency, especially at shorter time scales, and has shown large increases of leaf water use efficiency with increased CO2. However, the magnitude of the effect is variable, and does not consistently agree with predictions from simple leaf gas exchange considerations. The longer the time scales considered, the less the information and the more the uncertainty in the response to CO2, because of the additional factors that have to be considered, such as changes in leaf area, respiration of non-photosynthetic tissues and soil evaporation. The need for more detailed studies of the interactions between plant evaporation, water supply, water status and growth is stressed, as increased CO2 can affect all of these either directly, or indirectly through feedbacks with leaf gas exchange, carbon partitioning, leaf growth, canopy development and root growth. 相似文献
7.
Responses in stomatal conductance to elevated CO2 in 12 grassland species that differ in growth form
Responses in stomatal conductance (g
st
) and leaf xylem pressure potential (
leaf
) to elevated CO2 (2x ambient) were compared among 12 tallgrass prairie species that differed in growth form and growth rate. Open-top chambers (OTCs, 4.5 m diameter, 4.0 m in height) were used to expose plants to ambient and elevated CO2 concentrations from April through November in undisturbed tallgrass prairie in NE Kansas (USA). In June and August,
leaf
was usually higher in all species at elevated CO2 and was lowest in adjacent field plots (without OTCs). During June, when water availability was high, elevated CO2 resulted in decreased g
st
in 10 of the 12 species measured. Greatest decreases in g
st
(ca. 50%) occurred in growth forms with the highest potential growth rates (C3 and C4 grasses, and C3 ruderals). In contrast, no significant decrease in g
st
was measured in the two C3 shrubs. During a dry period in September, reductions in g
st
at elevated CO2 were measured in only two species (a C3 ruderal and a C4 grass) whereas increased g
st
at elevated CO2 was measured in the shrubs and a C3 forb. These increases in g
st
were attributed to enhanced
leaf
in the elevated CO2 plants resulting from increased soil water availability and/or greater root biomass. During a wet period in September, only reductions in g
st
were measured in response to elevated CO2. Thus, there was significant interspecific variability in stomatal responses to CO2 that may be related to growth form or growth rate and plant water relations. The effect of growth in the OTCs, relative to field plants, was usually positive for g
st
and was greatest (>30%) when water availability was low, but only 6–12% when
leaf
was high.The results of this study confirm the importance of considering interactions between indirect effects of high CO2 of plant water relations and direct effects of elevated CO2 on g
st
, particularly in ecosystems such as grasslands where water availability often limits productivity. A product of this interaction is that the potential exists for either positive or negative responses in g
st
to be measured at elevated levels of CO2. 相似文献
8.
George T. Byrd T. Loboda Clanton C. Black Jr. R. Harold Brown 《Photosynthesis research》1995,44(3):253-260
Onion (Allium cepa L.) plants were examined to determine the photosynthetic role of CO2 that accumulates within their leaf cavities. Leaf cavity CO2 concentrations ranged from 2250 L L–1 near the leaf base to below atmospheric (<350 L L–1) near the leaf tip at midday. There was a daily fluctuation in the leaf cavity CO2 concentrations with minimum values near midday and maximum values at night. Conductance to CO2 from the leaf cavity ranged from 24 to 202 mol m–2 s–1 and was even lower for membranes of bulb scales. The capacity for onion leaves to recycle leaf cavity CO2 was poor, only 0.2 to 2.2% of leaf photosynthesis based either on measured CO2 concentrations and conductance values or as measured directly by 14CO2 labeling experiments. The photosynthetic responses to CO2 and O2 were measured to determine whether onion leaves exhibited a typical C3-type response. A linear increase in CO2 uptake was observed in intact leaves up to 315 L L–1 of external CO2 and, at this external CO2 concentration, uptake was inhibited 35.4±0.9% by 210 mL L–1 O2 compared to 20 mL L–1 O2. Scanning electron micrographs of the leaf cavity wall revealed degenerated tissue covered by a membrane. Onion leaf cavity membranes apparently are highly impermeable to CO2 and greatly restrict the refixation of leaf cavity CO2 by photosynthetic tissue.Abbreviations Ca
external CO2 concentration
- Ci
intercellular CO2 concentration
-
CO2 compensation concentration
- PPFR
photosynthetic photon fluence rate 相似文献
9.
Shi-Rong Liu Craig Barton Helen Lee Paul G. Jarvis Dave Durrant 《Plant biosystems》2013,147(2):189-198
ABSTRACT After a 3-year exposure to elevated CO2, young trees of Sitka spruce (Picea sitchensis (Bong.) Carr.) were planted in native, nutrient-deficient forest soil and grown for two more years with three CO2 treatments in open-top chambers, and with two nutrient treatments (with and without supplied N). Elevated CO2 resulted in larger fresh mass, dry mass, leaf area and leaf thickness in two-year old needles, but had no effect on one-year old and current needles. Tree height, basal diameter and biomass production also increased, regardless of N supply. In trees without added N, elevated CO2 resulted in higher root-to-shoot and absorbing roots-to-stump ratios. Regardless of N supply, trees grown in elevated CO2 had lower photosynthetic rates on a leaf area basis. Photosynthesis reduction was accompanied by a decline in Rubisco activity and leaf N concentration. Under elevated CO2, added N elevated photosynthesis and Rubisco activity, suggesting a dependence on N availability of the photosynthetic response to elevated CO2. Stomatal conductance of trees grown with added N decreased in response to elevated CO2. This may account for the larger reduction in intercellular CO2 concentration, and hence photosynthesis, in the trees supplied with N than in those without N supply. 相似文献
10.
The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 µmol mol–1) and elevated (700 µmol mol–1) atmospheric CO2 concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm3 CO2 100g dry weight soil–1 in soils amended with sorghum grown under either elevated or ambient CO2. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test;p>0.05) in soils amended with sorghum grown under elevated CO2 concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO2. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling. 相似文献
11.
Johee Yoon Masayo Abe-Suzuki Pudjadi Eko Hiroshi Tamai Shigeichiro Hanamitsu Kaneyuki Nakane 《Ecological Research》2006,21(1):117-125
The hydroxyl (OH) radical, which is generated in polluted dew water on leaf surfaces of the Japanese apricot (Prunus mume), is known to be a potent oxidant. In order to investigate the effects of the OH radical formed in polluted dew water on the photosynthesis and growth of 3-year-old seedlings of P. mume, OH radical-generating solutions simulating polluted dew water were sprayed in the early morning as a mist throughout a growing season onto the leaf surfaces of seedlings growing in experimental greenhouses. Four OH radical-generating solutions (0, 6, 18 and 54 M H2O2 with Fe(III) and an oxalate ion) were used in the mist treatment. Five months after the beginning of treatment, the leaves exposed to the mist containing 54 M H2O2 showed a significantly smaller maximum CO2 assimilation rate (Amax) and stomatal conductance (gs) as compared to the leaves exposed to the mist containing 0 M H2O2. Exposure of P. mume seedlings to the OH radical-generating mist had caused a reduction in the dry weight and relative growth rate (RGR) of the above-ground parts (stem + branch) at the end of the growing season. A significant positive correlation was shown between RGR and Amax. Thus, the effects of oxidants generated in polluted dew water on leaf surfaces can be considered to be a cause of the decrease in leaf photosynthesis and growth of P. mume. 相似文献
12.
Mauro Centritto 《Plant biosystems》2013,147(2):177-188
ABSTRACT Peach (Prunus persica L.) seedlings were germinated and grown for two growing seasons either in open top chambers (OTC) with ambient (350 μmol mol-1) or elevated (700 μmol mol-1) [CO2], or in an outside control plot, all located inside a glasshouse. The seedlings were grown in 10 dm3 pots and were fertilised once a week following Ingestad principles in order to supply mineral nutrients at free access rates. In the second growing season, rapid onset of water stress was imposed on rapidly growing peach seedlings by withholding water for a four-week drying cycle. In elevated [CO2], seedlings had a total dry mass which was 33% higher than that in ambient [CO2]. This increase was largely a consequence of increased height growth. [CO2] and irrigation treatments had only small effects on allocation, and there was no increase in root allocation with low water availability possibly as consequence of the high-nutrient regime. Specific leaf area was significantly reduced in elevated [CO2], and probably resulted from increases in starch concentrations. Stomatal conductance (g s) was not affected by elevated [CO2] both in well-watered and water-stressed seedlings. The combination of increased assimilation rate (A) and unchanged g s led to large increases in intrinsic water use efficiency in response to elevated [CO2]. The A/C i curves were used to derive the parameters describing photosynthetic capacity, Amax, Jmax and Vcmax . These parameters were similar among [CO2] treatments; thus, there was no downward acclimation of photosynthesis in elevated [CO2]. Moreover, Amax, Jmax and Vcmax scaled linearly with leaf N content per unit leaf area. This indicates that the whole-plant source-sink balance of peach seedlings was not disrupted by growth in elevated [CO2], because root volume and nutrient supply were non-restricting. These values may be used in scaling up models to improve their ability to predict the magnitude of tree responses to climate change in the Mediterranean area. 相似文献
13.
The response ofPlantago major ssp,pleiosperma plants, grown on nutrient solution in a climate chamber, to a doubling of the ambient atmospheric CO2 concentration was investigated. Total dry matter production was increased by 30% after 3 weeks of exposure, due to a transient stimulation of the relative growth rate (RGR) during the first 10 days. Thereafter RGR returned to the level of control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the first two weeks of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root respiration was not affected by increased atmospheric CO2 levels, whereas shoot, dark respiration was stimulated throughout the experimental period. Dry matter allocation over leaves stems and roots was not affected by the CO2 level. SLA was reduced by 10%, which can partly be explained by an increased dry matter content of the leaves. Both in the early and later stages of the experiment, shoot respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric CO2. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf growth accounted for nearly 50% of the C budget at all stages of the experiment and in both treatments.Abbreviations LAR
leaf area ratio
- LWR
leaf weight ratio
- RGR
relative growth rate
- R/S
root to shoot ratio
- RWR
root weight ratio
- SLA
specific leaf area
- SWR
stem weight ratio 相似文献
14.
This paper examines the extent to which atmospheric CO2 enrichment may influence growth of plant roots and function in terms of uptake of water and nutrients, and carbon allocation towards symbionts. It is concluded that changes in dry matter allocation greatly depend on the experimental conditions during the experiment, the growth phase of the plant, and its morphological characteristics. Under non-limiting conditions of water and nutrients for growth, dry matter partitioning to the root is not changed by CO2 enrichment. The increase in root/shoot ratio, frequently observed under limiting conditions of water and/or nutrients, enables the plant to explore a greater soil volume, and hence acquire more water and nutrients. However, more data on changes in dry matter allocation within the root due to atmospheric CO2 are needed. It is concluded that nitrogen fixation is favored by CO2 enrichment since nodule mass is increased, concomitant with an increase in root length. The papers available so far on the influence of CO2 enrichment on mycorrhizal functioning suggest that carbon allocation to the roots might be increased, but also here more experiments are needed.Abbreviations LAR
leaf area ratio
- LWR
leaf weight ratio
- SWR
stem weight ratio
- RGR
relative growth rate
- R/S
root/shoot
- RWR
root weight ratio 相似文献
15.
A better understanding of the growth and interspecific competition of native dominant species under water stress should aid in prediction of succession in plant communities. In addition, such research would guide the selection of appropriate conservation and agricultural utilization of plants in semiarid environments that have not been very well characterized. Biomass production and allocation, relative competitive ability and water use efficiency of one C4 herbaceous grass (Bothriochloa ischaemum) and one C3 leguminous subshrub (Lespedeza davurica), both important species from the semiarid Loess Plateau of China, were investigated in a pot-cultivation experiment. The experiment was conducted using a replacement series design in which B. ischaemum and L. davurica were grown with twelve plants per pot, in seven combinations of the two species (12:0, 10:2, 8:4, 6:6, 4:8, 2:10, and 0:12). Three levels of water treatments included sufficient water supply (HW), moderate water stress (MW) and severe water stress (LW). These treatments were applied after seedling establishment and remained until the end of the experiment. Biomass production and its partitioning, and transpiration water use efficiency (TWUE) were determined at the end of the experiment. Interspecific competitive indices (competitive ratio (CR), aggressiveness (A) and relative yield total (RYT)) were calculated from the dry weight for shoots, roots and total biomass. Water stress decreased biomass production of both species in monoculture and mixture. The growth of L. davurica was restrained in their mixtures for each water treatment. L. davurica had significantly (P < 0.05) greater root:shoot allocation than B. ischaemum for each water treatment and proportion within the replacement series. Aggressiveness (A) values for B. ischaemum with respect to L. davurica were negative only at the proportions of B. ischaemum to L. davurica being 8:4 and 10:2 in LW treatment. B. ischaemum had a significantly (P < 0.05) higher CR value under each water treatment, and water stress considerably reduced its relative CR while increased that of L. davurica. RYT values of the two species indicated some degree of resource complimentarity under both water sufficient and deficit conditions. The results suggest that it is advantageous for growing the two species together to maximize biomass production, and the suggested ratio was 10:2 of B. ischaemum to L. davurica because of significantly higher (P < 0.05) RYT and TWUE under low water availability condition. 相似文献
16.
Mangroves, woody halophytes restricted to protected tropical coasts, form some of the most productive ecosystems in the world, but their capacity to act as a carbon source or sink under climate change is unknown. Their ability to adjust growth or to function as potential carbon sinks under conditions of rising atmospheric CO2 during global change may affect global carbon cycling, but as yet has not been investigated experimentally. Halophyte responses to CO2 doubling may be constrained by the need to use carbon conservatively under water-limited conditions, but data are lacking to issue general predictions. We describe the growth, architecture, biomass allocation, anatomy, and photosynthetic physiology of the predominant neotropical mangrove tree, Rhizophora mangle L., grown solitarily in ambient (350 ll–1) and double-ambient (700 ll–1) CO2 concentrations for over 1 year. Mangrove seedlings exhibited significantly increased biomass, total stem length, branching activity, and total leaf area in elevated CO2. Enhanced total plant biomass under high CO2 was associated with higher root:shoot ratios, relative growth rates, and net assimilation rates, but few allometric shifts were attributable to CO2 treatment independent of plant size. Maximal photosynthetic rates were enhanced among high-CO2 plants while stomatal conductances were lower, but the magnitude of the treatment difference declined over time, and high-CO2 seedlings showed a lower Pmax at 700 ll–1 CO2 than low-CO2 plants transferred to 700 ll–1 CO2: possible evidence of downregulation. The relative thicknesses of leaf cell layers were not affected by treatment. Stomatal density decreased as epidermal cells enlarged in elevated CO2. Foliar chlorophyll, nitrogen, and sodium concentrations were lower in high CO2. Mangroves grown in high CO2 were reproductive after only 1 year of growth (fully 2 years before they typically reproduce in the field), produced aerial roots, and showed extensive lignification of the main stem; hence, elevated CO2 appeared to accelerate maturation as well as growth. Data from this long-term study suggest that certain mangrove growth characters will change flexibly as atmospheric CO2 increases, and accord with responses previously shown in Rhizophora apiculata. Such results must be integrated with data from sea-level rise studies to yield predictions of mangrove performance under changing climate. 相似文献
17.
Decomposition of tree leaf litters grown under elevated CO2: Effect of litter quality 总被引:4,自引:0,他引:4
Ash (Fraxinus excelsior L.), birch (Betula pubescens Ehrh.), sycamore (Acer pseudoplatanus L.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) leaf litters were monitored for decomposition rates and nutrient release in a laboratory microcosm experiment. Litters were derived from solar domes where plants had been exposed to two different CO2 regimes: ambient (350 L L-1 CO2) and enriched (600 L L-1 CO2).Elevated CO2 significantly affected some of the major litter quality parameters, with lower N, higher lignin concentrations and higher ratios of C/N and lignin/N for litters derived from enriched CO2. Respiration rates of the deciduous species were significantly decreased for litters grown under elevated CO2, and reductions in mass loss at the end of the experiment were generally observed in litters derived from the 600 ppm CO2 treatment. Nutrient mineralization, dissolved organic carbon, and pH in microcosm leachates did not differ significantly between the two CO2 treatments for any of the species studied. Litter quality parameters were examined for correlations with cumulative respiration and decomposition rates: N concentration, C/N and lignin/N ratios showed the highest correlations, with differences between litter types. The results indicate that higher C storage will occur in soil as a consequence of litter quality changes resulting from higher atmospheric concentrations of CO2.Abbreviations CHO
soluble carbohydrates
- DOC
dissolved organic carbon
- HCel
holocellulose
- WTREM
weight remaining 相似文献
18.
揭示作物光合作用、蒸腾作用和水分利用效率(WUE)对大气CO2浓度变化的响应, 对预测未来大气CO2浓度升高条件下作物生产力与需水规律的变化具有重要意义。在自然CO2浓度、CO2倍增和倍增后恢复到自然CO2浓度3种情况下, 对大豆(Glycine max)、甘薯(Ipomoea batatas)、花生(Arachis hypogaea)、水稻(Oryza sativa)、棉花(Gossypium hirsutum)、玉米(Zea mays)、高粱(Sorghum vulgare)和谷子(Setaria italica) 8种作物的气体交换参数进行了研究。结果表明: CO2浓度倍增可以提高光合速率, 降低蒸腾速率, 从而提高WUE, 其中光合速率提高的贡献更大; C3比C4作物的光合速率、WUE增幅大, C3作物光合速率提高对WUE的贡献大于C4作物; 通过对比倍增后恢复到自然CO2浓度时气体交换参数随环境条件变化的响应确定了其内在调控机制; 倍增后恢复到自然CO2浓度时作物光合速率低于自然CO2浓度下的光合速率, 而蒸腾速率无明显差异。由此判断: CO2浓度倍增下存在光合下调现象, 这可能是由于Rubisco酶蛋白含量、活化水平和比活性降低等“非气孔因素”造成的, 并非由气孔导度的降低引起的。 相似文献
19.
Open-top chambers were used to study the effects of CO2 enrichment on leaf-level photosynthetic rates of the C4 grass Andropogon gerardii in the native tallgrass prairie ecosystem near Manhattan, Kansas. Measurements were made during a year with abundant rainfall
(1993) and a year with below-normal rainfall (1994). Treatments included: No chamber, ambient CO2 (A); chamber with ambient CO2 (CA); and chamber with twice-ambient CO2 (CE). Measurements of photosynthesis were made at 2-hour intervals, or at midday, on cloudless days throughout the growing
season using an open-flow gas-exchange system. No significant differences in midday rates of photosynthesis or in daily carbon
accumulation as a result of CO2 enrichment were found in the year with abundant precipitation. In the dry year, midday rates of photosynthesis were significantly
higher in the CE treatment than in the CA or A treatments throughout the season. Estimates of daily carbon accumulation also
indicated that CO2 enrichment allowed plants to maximize carbon acquisition on a diurnal basis. The increased carbon accumulation was accounted
for by greater rates of photosynthesis in the CE plots during midday. During the wet year, CO2 enrichment decreased stomatal conductance, which allowed plants to decrease transpiration while still photosynthesizing at
rates similar to plants in ambient conditions. During the dry year, CO2 enrichment allowed plants to maintain photosynthetic rates even though stomatal conductance and transpiration had been reduced
in all treatments due to stress. Estimates of instantaneous water-use efficiency were reduced under CO2 enrichment for both years.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
Elymus athericus (Link) Kerguélen, a C3 grass, was grown in a greenhouse experiment to determine the effect of enhanced atmospheric CO2 and elevated UV-B radiation levels on plant growth. Plants were subjected to the following treatments; a) ambient CO2-control UV-B, b) ambient CO2-elevated UV-B, c) double CO2-control UV-B, d) double CO2-elevated UV-B. Elevated CO2 concentrations stimulated plant growth, biomass production was 67% higher than at ambient CO2. Elevated UV-B radiation had a negative effect on growth, biomass production was depressed by 31%. Enhanced CO2 combined with elevated UV-B levels caused a biomass depression of 8% when compared with the control plants. UV-B induced growth depression can be modified by a growth stimulus caused by high CO2 concentrations. Growth analysis has been performed and possible physiological mechanisms behind changing growth parameters are discussed. 相似文献