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1.
For the leaf succulent Agave deserti and the stem succulent Ferocactus acanthodes, increasing the ambient CO 2 level from 350 microliters per liter to 650 microliters per liter immediately increased daytime net CO 2 uptake about 30% while leaving nighttime net CO 2 uptake of these Crassulacean acid metabolism (CAM) plants approximately unchanged. A similar enhancement of about 30% was found in dry weight gain over 1 year when the plants were grown at 650 microliters CO 2 per liter compared with 350 microliters per liter. Based on these results plus those at 500 microliters per liter, net CO 2 uptake over 24-hour periods and dry weight productivity of these two CAM succulents is predicted to increase an average of about 1% for each 10 microliters per liter rise in ambient CO 2 level up to 650 microliters per liter. 相似文献
2.
The effects of elevated CO 2 on nutrient cycling and selected belowground processes in the closed-canopy sweetgum plantation were assessed as part of a free-air CO 2 enrichment (FACE) experiment at Oak Ridge, Tennessee. We hypothesized that nitrogen (N) constraints to growth response to elevated CO 2 would be mitigated primarily by reduced tissue concentrations (resulting in increased biomass production per unit uptake) rather than increased uptake. Conversely, we hypothesized that the constraints of other nutrients to growth response to elevated CO 2 would be mitigated primarily by increased uptake because of adequate soil supplies. The first hypothesis was not supported: although elevated CO 2 caused reduced foliar N concentrations, it also resulted in increased uptake and requirement of N, primarily because of greater root turnover. The additional N uptake with elevated CO 2 constituted between 10 and 40% of the estimated soil mineralizeable N pool. The second hypothesis was largely supported: elevated CO 2 had no significant effects on tissue concentrations of P, K, Ca, or Mg and caused significantly increased uptake and requirement of K, Ca, and Mg. Soil exchangeable pools of these nutrients are large and should pose no constraint to continued growth responses. Elevated CO 2 also caused increased microbial biomass, reduced N leaching and increased P leaching from O horizons (measured by resin lysimeters), reduced soil solution NH
4
+
, SO
4
2–
, and Ca 2+ concentrations, and increased soil solution pH. There were no statistically significant treatment effects on soil nutrient availability as measured by resin capsules, resin stakes, or in situ incubations. Despite significantly lower litterfall N concentrations in the elevated CO 2 treatment, there were no significant treatment effects on translocation or forest floor biomass or nutrient contents. There were also no significant treatment effects on the rate of decomposition of fine roots. In general, the effects of elevated CO 2 on nutrient cycling in this study were not large; future constraints on growth responses imposed by N limitations will depend on changes in N demand, atmospheric N deposition, and soil mineralization rates. 相似文献
3.
Pinus radiata D. Don (half-sib families 20010 and 20062) and Pinus caribaea var hondurensis (an open-pollinated family) were grown for 49 weeks at seven levels of phosphorus and at CO 2 concentrations of either 340 or 660 microliters per liter, to establish if the phosphorus requirements differed between the CO 2 concentrations and if mycorrhizal associations were affected. When soil phosphorus availability was low, phosphorus uptake was increased by elevated CO 2. This may have been related to changes in mycorrhizal competition. When the phosphorus concentration in the youngest fully expanded needles was above 600 milligrams per kilogram the shoot weight of all pine families was greater at high CO 2 due to increases in rates of photosynthesis. More dry weight was partitioned to the stems of P. radiata family 20010 and P. caribaea. At foliar phosphorus concentrations above 1000 milligrams per kilogram ( P. radiata) and 700 milligrams per kilogram ( P. caribaea), growth did not increase at 340 microliters of CO 2 per liter. Soluble sugar levels in the same needles mirrored the growth response, but the starch concentration declined with increasing phosphorus. At 660 microliters of CO 2 per liter, shoot weight and soluble sugar concentrations were still increasing up to a foliar P concentration of 1800 milligrams per kilogram for P. radiata and 1600 milligrams per kilogram for P. caribaea. The starch concentrations did not decline. These results indicate that higher foliar phosphorus concentrations are required to realize the maximum growth potential of pines at elevated CO 2. 相似文献
4.
Carbon dioxide enrichment may increase the Al tolerance of trees by increasing root growth, root exudation and/or mycorrhizal
colonization. The effect of elevated CO 2 on the response of mycorrhizal pitch pine ( Pinus rigida Mill.) seedlings to Al was determined in two experiments with different levels of nutrients, 0.1- or 0.2-strength Clark solution.
During each experiment, seedlings inoculated with the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch were grown 13 weeks in sand irrigated with nutrient solution (pH 3.8) containing 0, 6.25, 12.5, or
25 mg/l Al (0, 232, 463, or 927 μM Al) in growth chambers fumigated with 350 (ambient) or 700 (elevated) μl/l CO 2. At ambient CO 2, in the absence of Al, mean total dry weights (DW) of seedlings at the high nutrient level were 164% higher than those at
the low level. Total DW at elevated CO 2, in the absence of Al, was significantly greater than that in ambient CO 2 at the low (+34%) and high (+16%) nutrient levels. Root and shoot DW at both nutrient levels decreased with increasing Al
concentrations with Al reducing root growth more than shoot growth. Although visible symptoms of Al toxicity in roots and
needles were reduced by CO 2 enrichment, there were no significant CO 2 × Al interactions for shoot or root DW. The percentage of seedling roots that became mycorrhizal was negatively related to
nutrient level and was greater at elevated than at ambient CO 2 levels. Generally, elevated CO 2 had little effect on concentration of mineral nutrients in roots and needles. Aluminum reduced concentrations of most nutrients
by inhibiting uptake.
Received: 18 June 1997 / Accepted: 8 December 1997 相似文献
5.
Growth at an elevated CO 2 concentration resulted in an enhanced capacity for soybean ( Glycine max L. Merr. cv Bragg) leaflet photosynthesis. Plants were grown from seed in outdoor controlled-environment chambers under natural solar irradiance. Photosynthetic rates, measured during the seed filling stage, were up to 150% greater with leaflets grown at 660 compared to 330 microliters of CO 2 per liter when measured across a range of intercellular CO 2 concentrations and irradiance. Soybean plants grown at elevated CO 2 concentrations had heavier pod weights per plant, 44% heavier with 660 compared to 330 microliters of CO 2 per liter grown plants, and also greater specific leaf weights. Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activity showed no response (mean activity of 96 micromoles of CO 2 per square meter per second expressed on a leaflet area basis) to short-term (~1 hour) exposures to a range of CO 2 concentrations (110-880 microliters per liter), nor was a response of activity (mean activity of 1.01 micromoles of CO 2 per minute per milligram of protein) to growth CO 2 concentration (160-990 microliters per liter) observed. The amount of rubisco protein was constant, as growth CO 2 concentration was varied, and averaged 55% of the total leaflet soluble protein. Although CO 2 is required for activation of rubisco, results indicated that within the range of CO 2 concentrations used (110-990 microliters per liter), rubisco activity in soybean leaflets, in the light, was not regulated by CO 2. 相似文献
6.
Carbon exchange rates (CER) and whole-plant carbon balances of beech ( Fagus grandifolia) and sugar maple ( Acer saccharum) were compared for seedlings grown under low irradiance to determine the effects of atmospheric CO 2 enrichment on shade-tolerant seedlings of co-dominant species. Under contemporary atmospheric CO 2, photosynthetic rate per unit mass of beech was lower than for sugar maple, and atmospheric CO 2 enrich ment enhanced photosynthesis for beech only. Aboveground respiration per unit mass decreased with CO 2 enrichment for both species while root respiration per unitmass decreased for sugar maple only. Under contemporary atmoapheric CO 2, beech had lower C uptake per plant than sugar maple, while C losses per plant to nocturnal aboveground and root respiration were similar for both species. Under elevated CO 2, C uptake per plant was similar for both species, indicating a significant relative increase in whole-seedling CER with CO 2 enrich ment for beech but not for sugar maple. Total C loss per plant to aboveground respiration was decreased for beech only because increase in sugar maple leaf mass counterbalanced a reduction in respiration rates. Carbon loss to root respiration per plant was not changed by CO 2 enrichment for either species. However, changes in maintenance respiration cost and nitrogen level suggest changes in tissue composition with elevated CO 2. Beech had a greater net daily C gain with CO 2 enrichment than did sugar maple in contrast to a lower one under contemporary CO 2. Elevated CO 2 preferentially enhances the net C balance of beech by increasing photosynthesis and reducing respiration cost. In all cases, the greatest C lost was by roots, indicating the importance of belowground biomass in net C gain. Relative growth rate estimated from biomass accumulation was not affected by CO 2 enrichment for either species possibly because of slow growth under low light. This study indicates the importance of direct effects of CO 2 enrichment when predicting potential change in species distribution with global climate change. 相似文献
7.
CO 2 concentrations of 1000 compared to 350 microliters per liter in controlled environment chambers did not increase total fruit weight or number in a monoecious cucumber ( Cucumis sativus L. cv Chipper) nor did it increase biomass, leaf area, or relative growth rates beyond the first 16 days after seeding. Average fruit weight was slightly, but not significantly greater in the 1000 microliters per liter CO 2 treatment because fruit numbers were changed more than total weight. Plants grown at 1000 and 350 microliters per liter CO 2 were similar in distribution of dry matter and leaf area between mainstem, axillary, and subaxillary branches. Early flower production was greater in 1000 microliters per liter plants. Subsequent flower numbers were either lower in enriched plants or similar in the two treatments, except for the harvest at fruiting when enriched plants produced many more male flowers than the 350 microliters per liter treatments. 相似文献
8.
The effects of CO 2-limited photosynthesis on 15NO 3− uptake and reduction by maize ( Zea mays, DeKalb XL-45) seedlings were examined in relation to concurrent effects of CO 2 stress on carbohydrate levels and in vitro nitrate reductase activities. During a 10-hour period in CO 2-depleted air (30 microliters of CO 2/ per liter), cumulative 15NO 3− uptake and reduction were restricted 22 and 82%, respectively, relative to control seedlings exposed to ambient air containing 450 microliters of CO 2 per liter. The comparable values for roots of decapitated maize seedlings, the shoots of which had previously been subjected to CO 2 stress, were 30 and 42%. The results demonstrate that reduction of entering nitrate by roots as well as shoots was regulated by concurrent photosynthesis. Although in vitro nitrate reductase activity of both tissues declined by 60% during a 10-hour period of CO 2 stress, the remaining activity was greatly in excess of that required to catalyze the measured rate of 15NO 3− reduction. Root respiration and soluble carbohydrate levels in root tissue were also decreased by CO 2 stress. Collectively, the results indicate that nitrate uptake and reduction were regulated by the supply of energy and carbon skeletons required to support these processes, rather than by the potential enzymatic capacity to catalyze nitrate reduction, as measured by in vitro nitrate reductase activity. 相似文献
9.
We hypothesized that greater photosynthate supply at elevated [CO 2] could compensate for increased below-ground C demands of arbuscular mycorrhizas. Therefore, we investigated plant growth,
mineral nutrition, starch, and net gas exchange responses of two Citrus spp. to phosphorus (P) nutrition and mycorrhizas at
elevated atmospheric [CO 2]. Half of the seedlings of sour orange (C. aurantium L.) and ‘Ridge Pineapple’ sweet orange (C. sinensis L. Osbeck) were
inoculated with the arbuscular mycorrhizal (AM) fungus, Glomus intraradices Schenck and Smith and half were non-mycorrhizal
(NM). Plants were grown at ambient or 2X ambient [CO 2] in unshaded greenhouses for 11 weeks and fertilized daily with nutrient solution either without added P or with 2 mM P in
a low-P soil. High P supply reduced AM colonization whereas elevated [CO 2] counteracted the depressive effect of P on intraradical colonization and vesicle development. Seedlings grown at either
elevated [CO 2], high P or with G. intraradices had greater growth, net assimilation of CO 2 (A
CO2) in leaves, leaf water-use efficiency, leaf dry wt/area, leaf starch and carbon/nitrogen (C/N) ratio. Root/whole plant dry
wt ratio was decreased by elevated [CO 2], P, and AM colonization. Mycorrhizal seedlings had higher leaf-P status but lower leaf N and K concentrations than nonmycorrhizal
seedlings which was due to growth dilution effects. Starch in fibrous roots was increased by elevated [CO 2] but reduced by G. intraradices, especially at low-P supply. In fibrous roots, elevated [CO 2] had no effect on C/N, but AM colonization decreased C/N in both Citrus spp. grown at low-P supply. Overall, there were no
species differences in growth or A
CO2. Mycorrhizas did not increase plant growth at ambient [CO 2]. At elevated [CO 2], however, mycorrhizas stimulated growth at both P levels in sour orange, the more mycorrhiza-dependent species, but only
at low-P in sweet orange, the less dependent species. At low-P and elevated [CO 2], colonization by the AM fungus increased A
CO2 in both species but more so in sour orange than in sweet orange. Leaf P and root N concentrations were increased more and
root starch level was decreased less by AM in sour orange than in sweet orange. Thus, the additional [CO 2] availability to mycorrhizal plants increased CO 2 assimilation, growth and nutrient uptake over that of NM plants especially in sour orange under P limitation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
This paper summarizes the data on nutrient uptake and soil responses in opentop chambers planted with ponderosa pine (Pinus ponderosa Laws.) treated with both N and CO 2. Based upon the literature, we hypothesized that 1) elevated CO 2 would cause increased growth and yield of biomass per unit uptake of N even if N is limiting, and 2) elevated CO 2 would cause increased biomass yield per unit uptake of other nutrients only by growth dilution and only if they are non-limiting. Hypothesis 1 was supported only in part: there were greater yields of biomass per unit N uptake in the first two years of growth but not in the third year. Hypothesis 2 was supported in many cases: elevated CO 2 caused growth dilution (decreased concentrations but not decreased uptake) of P, S, and Mg. Effects of elevated CO 2 on K, Ca, and B concentrations were smaller and mostly non-significant. There was no evidence that N responded in a unique manner to elevated CO 2, despite its unique role in rubisco. Simple growth dilution seemed to explain nutrient responses in almost all cases.There were significant declines in soil exchangeable K +, Ca 2+, Mg 2+ and extractable P over time which were attributed to disturbance effects associated with plowing. The only statistically significant treatment effects on soils were negative effects of elevated CO 2 on mineralizeable N and extractable P, and positive effects of both N fertilization and CO 2 on exchangeable Al 3+. Soil exchangeable K +, Ca 2+, and Mg 2+ pools remained much higher than vegetation pools, but extractable P pools were lower than vegetation pools in the third year of growth. There were also large losses of both native soil N and fertilizer N over time. These soil N losses could account for the observed losses in exchangeable K +, Ca 2+, Mg 2+ if N was nitrified and leached as NO
3
–
. 相似文献
11.
Carbon exchange capacity of cucumber ( Cucumis sativus L.) germinated and grown in controlled environment chambers at 1000 microliters per liter CO 2 decreased from the vegetative growth stage to the fruiting stage, during which time capacity of plants grown at 350 microliters per liter increased. Carbon exchange rates (CERs) measured under growth conditions during the fruiting period were, in fact, lower in plants grown at 1000 microliters per liter CO 2 than those grown at 350. Progressive decreases in CERs in 1000 microliters per liter plants were associated with decreasing stomatal conductances and activities of ribulose bisphosphate carboxylase and carbonic anhydrase. Leaf starch concentrations were higher in 1000 microliters per liter CO 2 grown-plants than in 350 microliters per liter grown plants but calcium and nitrogen concentrations were lower, the greatest difference occurring at flowering. Sucrose synthase and sucrose-P-synthase activities were similar in 1000 microliters per liter compared to 350 microliters per liter plants during vegetative growth and flowering but higher in 350 microliters per liter plants at fruiting. The decreased carbon exchange rates observed in this cultivar at 1000 microliters per liter CO 2 could explain the lack of any yield increase (MM Peet 1986 Plant Physiol 80: 59-62) when compared with plants grown at 350 microliters per liter. 相似文献
12.
Atmospheric CO 2 enrichment is expected to often benefit plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate (NO 3?) or ammonium (NH 4+), using membrane‐localized transport proteins in roots, which are key targets for improving N use. Although interactive effects of elevated CO 2, chronic warming and N form on N relations are expected, these have not been studied. In this study, tomato ( Solanum lycopersicum) plants were grown at two levels of CO 2 (400 or 700 ppm) and two temperature regimes (30 or 37°C), with NO 3? or NH 4+ as the N source. Elevated CO 2 plus chronic warming severely inhibited plant growth, regardless of N form, while individually they had smaller effects on growth. Although %N in roots was similar among all treatments, elevated CO 2 plus warming decreased (1) N‐uptake rate by roots, (2) total protein concentration in roots, indicating an inhibition of N assimilation and (3) shoot %N, indicating a potential inhibition of N translocation from roots to shoots. Under elevated CO 2 plus warming, reduced NO 3?‐uptake rate per g root was correlated with a decrease in the concentration of NO 3?‐uptake proteins per g root, reduced NH 4+ uptake was correlated with decreased activity of NH 4+‐uptake proteins and reduced N assimilation was correlated with decreased concentration of N‐assimilatory proteins. These results indicate that elevated CO 2 and chronic warming can act synergistically to decrease plant N uptake and assimilation; hence, future global warming may decrease both plant growth and food quality (%N). 相似文献
13.
The effect of sink strength on photosynthetic rates under conditions of long-term exposure to high CO 2 has been investigated in soybean. Soybean plants (Merr. cv. Fiskeby V) were grown in growth chambers containing 350 microliters CO 2 per liter air until pod set. At that time, plants were trimmed to three trifoliolate leaves and either 21 pods (high sink treatment) or 6 pods (low sink treatment). Trimmed plants were either left in 350 microliters CO 2 per liter of air or placed in 1000 microliters CO 2 per liter of air (high CO 2 treatment) until pod maturity. Whole plant net photosynthetic rates of all plants were measured twice weekly, both at 350 microliters CO 2 per liter of air and 1000 microliters CO 2 per liter of air. Plants were also harvested at this time for dry weight measurements. Photosynthetic rates of high sink plants at both measurement CO 2 concentrations were consistently higher than those of low sink plants, and those of plants given the 350 microliter CO 2 per liter of air treatment were higher at both measurement CO 2 concentrations than those of plants given the 1000 microliters CO 2 per liter of air treatment. When plants were measured under treatment CO 2 levels, however, rates were higher in 1,000 microliter plants than 350 microliter CO 2 plants. Dry weights of all plant parts were higher in the 1,000 microliters CO 2 per liter air treatment than in the 350 microliters CO 2 per liter air treatment, and were higher in the low sink than in the high sink treatments. 相似文献
14.
The submerged aquatic plant Isoetes howellii Engelmann possesses Crassulacean acid metabolism (CAM) comparable to that known from terrestrial CAM plants. Infrared gas analysis of submerged leaves showed Isoetes was capable of net CO 2 uptake in both light and dark. CO 2 uptake rates were a function of CO 2 levels in the medium. At 2,500 microliters CO 2 per liter (gas phase, equivalent to 1.79 milligrams per liter aqueous phase), Isoetes leaves showed continuous uptake in both the light and dark. At this CO 2 level, photosynthetic rates were light saturated at about 10% full sunlight and were about 3-fold greater than dark CO 2 uptake rates. In the dark, CO 2 uptake rates were also a function of length of time in the night period. Measurements of dark CO 2 uptake showed that, at both 2,500 and 500 microliters CO 2 per liter, rates declined during the night period. At the higher CO 2 level, dark CO 2 uptake rates at 0600 h were 75% less than at 1800 h. At 500 microliters CO 2 per liter, net CO 2 uptake in the dark at 1800 h was replaced by net CO 2 evolution in the dark at 0600 h. At both CO 2 levels, the overnight decline in net CO 2 uptake was marked by periodic bursts of accelerated CO 2 uptake. CO 2 uptake in the light was similar at 1% and 21% O 2, and this held for leaves intact as well as leaves split longitudinally. Estimating the contribution of light versus dark CO 2 uptake to the total carbon gain is complicated by the diurnal flux in CO 2 availability under field conditions. 相似文献
15.
Summary Seeds of Gliricidia sepium (Jacq.) Walp., a tree native to seasonal tropical forests of Central America, were inoculated with N-fixing Rhizobium bacteria and grown in growth chambers for 71 days to investigate interactive effects of atmospheric CO 2 and plant N status on early seedling growth, nodulation, and N accretion. Seedlings were grown with CO 2 partial pressures of 350 and 650 bar (current ambient and a predicted partial pressure of the mid-21st century) and with plus N or minus N nutrient solutions to control soil N status. Of particular interest was seedling response to CO 2 when grown without available soil N, a condition in which seedlings initially experienced severe N deficiency because bacterial N-fixation was the sole source of N. Biomass of leaves, stems, and roots increased significantly with CO 2 enrichment (by 32%, 15% and 26%, respectively) provided seedlings were supplied with N fertilizer. Leaf biomass of N-deficient seedlings was increased 50% by CO 2 enrichment but there was little indication that photosynthate translocation from leaves to roots or that plant N (fixed by Rhizobium) was altered by elevated CO 2. In seedlings supplied with soil N, elevated CO 2 increased average nodule weight, total nodule weight per plant, and the amount of leaf nitrogen provided by N-fixation (as indicated by leaf 15N). While CO 2 enrichment reduced the N concentration of some plant tissues, whole plant N accretion increased. Results support the contention that increasing atmospheric CO 2 partial pressures will enhance productivity and N-fixing activity of N-fixing tree seedlings, but that the magnitude of early seedling response to CO 2 will depend greatly on plant and soil nutrient status. 相似文献
16.
Young bean plants ( Phaseolus vulgaris L. cv Seafarer) grew faster in air enriched with CO 2 (1200 microliters per liter) than in ambient CO 2 (330 microliters per liter). However, by 7 days when increases in overall growth (dry weight, leaf area) were visible, there was a significant decline (about 25%) in the leaf mineral content (N, P, K, Ca, Mg) and a drop in the activity of two enzymes of carbon fixation, carbonic anhydrase and ribulose 1,5-bisphosphate (RuBP) carboxylase under high CO 2. Although the activity of neither enzyme was altered in young, expanding leaves during the acclimation period, in mature leaves the activity of carbonic anhydrase was reduced 95% compared with a decline of 50% in ambient CO 2. The drop in RuBP carboxylase was less extreme with 40% of the initial activity retained in the high CO 2 compared with 50% in the ambient atmosphere. While CO 2 enrichment might alter the flow of carbon into the glycolate pathway by modifying the activities of carbonic anhydrase or RuBP carboxylase, there is no early change in the ability of photosynthetic tissue to oxidize glycolate to CO 2. 相似文献
17.
A series of laboratory exposures of two varieties of bush bean ( Phaseolus vulgaris L., var 274 and var 290) was conducted to determine the sensitivity of [ 14C]photosynthate allocation patterns to alteration by SO 2 and O 3. Experiments with the pollution-resistant 274 variety demonstrated short-term changes in both 14C and biomass allocation to roots of 14CO 2-labeled plants but no significant effect on yield by up to 40 hours of exposure to SO 2 at 0.50 microliters per liter or 4 hours of O 3 at 0.40 microliters per liter. Subsequent experiments with the more sensitive 290 variety demonstrated significant alteration of photosynthesis, translocation, and partitioning of photosynthate between plant parts including developing pods. Significant increases in foliar retention of photosynthate (+40%) occurred after 8 hours of exposure to SO 2 at 0.75 microliters per liter (6.0 microliters per liter-hour) and 11 hours of exposure to O 3 at 0.30 microliters per liter-hour (3.3 microliters-hours). Time series sampling of labeled tissues after 14CO 2 uptake showed that the disruption of translocation patterns was persistent for at least 1 week after exposures ceased. Subsequent longer-term exposures at lower concentrations of both O 3 (0.0, 0.10, 0.15, and 0.20 microliters per liter) and SO 2 (0.0, 0.20, and 0.40 microliters per liter) demonstrated that O 3 more effectively altered allocation than SO 2, that primary leaves were generally more sensitive than trifoliates, and that responses of trifoliate leaves varied with plant growth stage. Altered rates of allocation of photosynthate by leaves were generally associated with alterations of similar magnitude and opposite direction in developing pods. Collectively, these experiments suggest that allocation patterns can provide sensitive indices of incipient growth responses of pollution-stressed vegetation. 相似文献
18.
Growth in elevated CO 2 often leads to decreased plant nitrogen contents and down-regulation of photosynthetic capacity. Here, we investigated whether elevated CO 2 limits nitrogen uptake when nutrient movement to roots is unrestricted, and the dependence of this limitation on nitrogen supply and plant development in durum wheat ( Triticum durum Desf.). Plants were grown hydroponically at two N supplies and ambient and elevated CO 2 concentrations. Elevated CO 2 decreased nitrate uptake per unit root mass with low N supply at early grain filling, but not at anthesis. This decrease was not associated with higher nitrate or amino acid, or lower non-structural carbohydrate contents in roots. At anthesis, elevated CO 2 decreased the nitrogen content of roots with both levels of N and that of aboveground organs with high N. With low N, elevated CO 2 increased N allocation to aboveground plant organs and nitrogen concentration per unit flag leaf area at anthesis, and per unit aboveground dry mass at both growth stages. The results from the hydroponic experiment suggest that elevated CO 2 restricts nitrate uptake late in development, high N supply overriding this restriction. Increased nitrogen allocation to young leaves at low N supply could alleviate photosynthetic acclimation to elevated CO 2. 相似文献
19.
Cotton ( Gossypium hirsutum L. cv Stoneville 213) was grown at 350 and 1000 microliters per liter CO 2. The plants grown at elevated CO 2 concentrations contained large starch pools and showed initial symptoms of visible physical damage. Photosynthetic rates were lower than expected based on instantaneous exposure to high CO 2. A group of plants grown at 1000 microliters per liter CO2 was switched to 350 microliters per liter CO2. Starch pools and photosynthetic rates were monitored in the switched plants and in the two unswitched control groups. Photosynthetic rates per unit leaf area recovered to the level of the 350 microliters per liter CO2 grown control group within four to five days. To assess only nonstomatal limitations to photosynthesis, a measure of photosynthetic efficiencies was calculated (moles CO2 fixed per square meter per second per mole intercellular CO2). Photosynthetic efficiency also recovered to the levels of the 350 microliters per liter CO2 grown controls within three to four days. Recovery was correlated to a rapid depletion of the starch pool, indicating that the inhibition of photosynthesis is primarily a result of feedback inhibition. However, complete recovery may involve the repair of damage to the chloroplasts caused by excessive starch accumulation. The rapid and complete reversal of photosynthetic inhibition suggests that the appearance of large, strong sinks at certain developmental stages could result in reduction of the large starch accumulations and that photosynthetic rates could recover to near the theoretical capacity during periods of high photosynthate demand. 相似文献
20.
Water hyacinth ( Eichhornia crassipes [Mart.] Solms) plants were grown in environmental chambers at ambient and enriched CO 2 levels (330 and 600 microliters CO 2 per liter). Daughter plants (ramets) produced in the enriched CO 2 gained 39% greater dry weight than those at ambient CO 2, but the original mother plants did not. The CO 2 enrichment increased the number of leaves per ramet and leaf area index, but did not significantly increase leaf size or the number of ramets formed. Flower production was increased 147%. The elevated CO 2 increased the net photosynthetic rate of the mother plants by 40%, but this was not maintained as the plants acclimated to the higher CO 2 level. After 14 days at the elevated CO 2, leaf resistance increased and transpiration decreased, especially from the adaxial leaf surface. After 4 weeks in elevated as compared to ambient CO 2, ribulose bisphosphate carboxylase activity was 40% less, soluble protein content 49% less, and chlorophyll content 26% less; whereas starch content was 40% greater. Although at a given CO 2 level the enriched CO 2 plants had only half the net photosynthetic rate of their counterparts grown at ambient CO 2, they showed similar internal CO 2 concentrations. This suggested that the decreased supply of CO 2 to the mesophyll, as a result of the increased stomatal resistance, was counterbalanced by a decreased utilization of CO 2. Photorespiration and dark respiration were lower, such that the CO 2 compensation point was not altered. The photosynthetic light and CO 2 saturation points were not greatly changed, nor was the O 2 inhibition of photosynthesis (measured at 330 microliters CO 2 per liter). It appears that with CO 2 enrichment the temporary increase in net photosynthesis produced larger ramets. After acclimation, the greater total ramet leaf area more than compensated for the lower net photosynthetic rate on a unit leaf area basis, and resulted in a sustained improvement in dry weight gain. 相似文献
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