共查询到20条相似文献,搜索用时 31 毫秒
1.
One-year-old plants of the CAM leaf succulent Agave vilmoriniana Berger were grown outdoors at Riverside, California. Potted plants were acclimated to CO 2-enrichment (about 750 microliters per liter) by growth for 2 weeks in an open-top polyethylene chamber. Control plants were grown nearby where the ambient CO 2 concentration was about 370 microliters per liter. When the plants were well watered, CO 2-induced differences in stomatal conductances and CO 2 assimilation rates over the entire 24-hour period were not large. There was a large nocturnal acidification in both CO 2 treatments and insignificant differences in leaf chlorophyll content. Well watered plants maintained water potentials of −0.3 to −0.4 megapascals. When other plants were allowed to dry to water potentials of −1.2 to −1.7 megapascals, stomatal conductances and CO 2 uptake rates were reduced in magnitude, with the biggest difference in Phase IV photosynthesis. The minor nocturnal response to CO 2 by this species is interpreted to indicate saturated, or nearly saturated, phosphoenolpyruvate carboxylase activity at current atmospheric CO 2 concentrations. CO 2-enhanced diurnal activity of ribulose bisphosphate carboxylase activity remains a possibility. 相似文献
2.
Large (about 200 grams dry weight) and small (about 5 grams dry weight) specimens of the leaf succulent Agave vilmoriniana Berger were grown outdoors at Phoenix, Arizona. Potted plants were maintained in open-top chambers constructed with clear, plastic wall material. Four CO 2 concentrations of 350, 560, 675, and 885 microliters per liter were used during two growth periods and two water treatments. Small and large plants were grown for 6 months, while a few large plants were grown for 1 year. Wet-treatment plants received water twice weekly, whereas dry-treatment plants received slightly more water than they would under natural conditions. Plant growth rates in all treatments were significantly different between small and large specimens, but not between 6 month and 1 year large plants. Only the dry-treatment plants exhibited statistically different growth rates between the CO 2 treatments. This productivity response was equivalent to a 28% and 3-fold increase when mathematically interpolated between CO 2 concentrations of 300 and 600 microliters per liter for large and small plants, respectively. 相似文献
3.
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
4.
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
5.
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
6.
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
7.
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
8.
Photosynthetic CO 2 and O 2 exchange was studied in two moss species, Hypnum cupressiforme Hedw. and Dicranum scoparium Hedw. Most experiments were made during steady state of photosynthesis, using 18O 2 to trace O 2 uptake. In standard experimental conditions (photoperiod 12 h, 135 micromoles photons per square meter per second, 18°C, 330 microliters per liter CO 2, 21% O 2) the net photosynthetic rate was around 40 micromoles CO 2 per gram dry weight per hour in H. cupressiforme and 50 micromoles CO 2 per gram dry weight per hour in D. scoparium. The CO 2 compensation point lay between 45 and 55 microliters per liter CO 2 and the enhancement of net photosynthesis by 3% O 2versus 21% O 2 was 40 to 45%. The ratio of O 2 uptake to net photosynthesis was 0.8 to 0.9 irrespective of the light intensity. The response of net photosynthesis to CO 2 showed a high apparent Km (CO 2) even in nonsaturating light. On the other hand, O 2 uptake in standard conditions was not far from saturation. It could be enhanced by only 25% by increasing the O 2 concentration (saturating level as low as 30% O 2), and by 65% by decreasing the CO 2 concentration to the compensation point. Although O 2 is a competitive inhibitor of CO 2 uptake it could not replace CO 2 completely as an electron acceptor, and electron flow, expressed as gross O 2 production, was inhibited by both high O 2 and low CO 2 levels. At high CO 2, O 2 uptake was 70% lower than the maximum at the CO 2 compensation point. The remaining activity (30%) can be attributed to dark respiration and the Mehler reaction. 相似文献
9.
Numerous net photosynthetic and dark respiratory measurements were made over a period of 4 years on leaves of 24 sour orange ( Citrus aurantium) trees; 8 of them growing in ambient air at a mean CO 2 concentration of 400 microliters per liter, and 16 growing in air enriched with CO 2 to concentrations approaching 1000 microliters per liter. Over this CO 2 concentration range, net photosynthesis increased linearly with CO 2 by more than 200%, whereas dark respiration decreased linearly to only 20% of its initial value. These results, together with those of a comprehensive fine-root biomass determination and two independent aboveground trunk and branch volume inventories, suggest that a doubling of the air's current mean CO 2 concentration of 360 microliters per liter would enhance the growth of the trees by a factor of 3.8. 相似文献
10.
Greenhouse-grown plants of Xanthium strumarium L. were exposed in a growth cabinet to 10 C during days and 5 C during nights for periods of up to 120 hours. Subsequently, CO 2 exchange, transpiration, and leaf temperature were measured on attached leaves and in leaf sections at 25 or 30 C, 19 C dew point of the air, 61 milliwatts per square centimeter irradiance, and CO 2 concentrations between 0 and 1000 microliters per liter ambient air. Net photosynthesis and stomatal conductance decreased and dark respiration increased with increasing duration of prechilling. The reduction in net photosynthesis was not a consequence of decreased stomatal conductance because the intercellular CO 2 concentration in prechilled leaves was equal to or greater than that in greenhouse-grown controls. The intercellular CO 2 concentration at which one-half maximum net photosynthesis occurred remained the same in prechilled leaves and controls (175 to 190 microliters per liter). Stomata of the control plants responded to changes in the CO 2 concentration of the air only slightly. Prechilling for 24 hours or more sensitized stomata to CO 2; they responded to changes in CO 2 concentration in the range from 100 to 1000 microliters per liter. 相似文献
11.
The rate of CO 2 assimilation and levels of metabolites of the C 4 cycle and reductive pentose phosphate pathway in attached leaves of maize ( Zea mays L.) were measured over a range of light intensity from 0 to 1,900 microEinsteins per square meter per second under a saturated CO 2 concentration of 350 microliters per liter and a limiting CO 2 concentration of 133 microliters per liter. The level of ribulose 1,5-bisphosphate (RuBP) stayed almost constant (around 60 nanomoles per milligram chlorophyll [Chl]) from low to high light intensities under 350 microliters per liter. Levels of 3-phosphoglycerate (PGA) increased from 100 to 650 nanomoles per milligram Chl under 350 microliters per liter CO 2 with increasing light intensity. The calculated RuBP concentration of 6 millimolar (corresponded to 60 nanomoles per milligram Chl) was about two times above the estimated RuBP binding-site concentration on ribulose bisphosphate carboxylase-oxygenase (Rubisco) of ~2.6 millimolar in maize bundle sheath chloroplasts in the light. The ratio of RuBP/PGA increased with decreasing light intensity under 350 microliters per liter CO 2. These results suggest that RuBP carboxylation is under control of light intensity possibly due to a limited supply of CO 2 to Rubisco through the C 4 cycle whose activity is highly dependent on light intensity. Pyruvate level increased with increasing light intensity as long as photosynthesis rate increased. A positive relationship between levels of PGA and those of pyruvate during steady-state photosynthesis under various conditions suggests that an elevated concentration of PGA increases the carbon input into the C 4 cycle through the conversion of PGA to PEP and consequently the level of total intermediates of the C 4 cycle can be raised to mediate higher photosynthesis rate. 相似文献
12.
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
13.
The CO 2 compensation point of the submersed aquatic macrophyte Hydrilla verticillata varied from high (above 50 microliters per liter) to low (10 to 25 microliters per liter) values, depending on the growth conditions. Plants from the lake in winter or after incubation in an 11 C/9-hour photoperiod had high values, whereas summer plants or those incubated in a 27 C/14-hour photoperiod had low values. The plants with low CO 2 compensation points exhibited dark 14CO 2 fixation rates that were up to 30% of the light fixation rates. This fixation reduced respiratory CO 2 loss, but did not result in a net uptake of CO 2 at night. The low compensation point plants also showed diurnal fluctuations in titratable acid, such as occur in Crassulacean acid metabolism plants. However, dark fixation and diurnal acid fluctuations were negligible in Hydrilla plants with high CO 2 compensation points. 相似文献
14.
During the period of most active leaf expansion, the foliar dark respiration rate of soybeans ( Glycine max cv Williams), grown for 2 weeks in 1000 microliters CO 2 per liter air, was 1.45 milligrams CO 2 evolved per hour leaf density thickness, and this was twice the rate displayed by leaves of control plants (350 microliters CO 2 per liter air). There was a higher foliar nonstructural carbohydrate level ( e.g. sucrose and starch) in the CO 2 enriched compared with CO 2 normal plants. For example, leaves of enriched plants displayed levels of nonstructural carbohydrate equivalent to 174 milligrams glucose per gram dry weight compared to the 84 milligrams glucose per gram dry weight found in control plant leaves. As the leaves of CO 2 enriched plants approached full expansion, both the foliar respiration rate and carbohydrate content of the CO 2 enriched leaves decreased until they were equivalent with those same parameters in the leaves of control plants. A strong positive correlation between respiration rate and carbohydrate content was seen in high CO 2 adapted plants, but not in the control plants. Mitochondria, isolated simultaneously from the leaves of CO2 enriched and control plants, showed no difference in NADH or malate-glutamate dependent O2 uptake, and there were no observed differences in the specific activities of NAD+ linked isocitrate dehydrogenase and cytochrome c oxidase. Since the mitochondrial O2 uptake and total enzyme activities were not greater in young enriched leaves, the increase in leaf respiration rate was not caused by metabolic adaptations in the leaf mitochondria as a response to long term CO2 enrichment. It was concluded, that the higher respiration rate in the enriched plant's foliage was attributable, in part, to a higher carbohydrate status. 相似文献
15.
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
16.
Crassulacean acid metabolism (CAM) was investigated in leaves and stems of the succulent C 4 dicot Portulaca oleracea L. Diurnal acid fluctuations, CO 2 gas exchange, and leaf resistance were monitored under various photoperiod and watering regimes. No CAM activity was seen in well watered plants grown under 16-hour days. Under 8-hour days, however, well watered plants showed a CAM-like pattern of acid fluctuation with amplitudes of 102 and 90 microequivalents per gram fresh weight for leaves and stems, respectively. Similar patterns were also observed in detached leaves and defoliated stems. Leaf resistance values indicated that stomata were open during part of the dark period, but night acidification most likely resulted from refixation of respiratory CO 2. In water-stressed plants maximum acid accumulations were reduced under both long and short photoperiods. At night, these plants showed short periods of net CO 2 uptake and stomatal opening which continued all night long during preliminary studies under natural environmental conditions. Greatest acid fluctuations, in P. oleracea, with amplitudes of 128 microequivalents per gram fresh weight, were observed in water-stressed plants which had been rewatered, especially when grown under short days. No net CO 2 uptake took place, but stomata remained open throughout the night under these conditions. These results indicate that under certain conditions, such as water stress or short photoperiods, P. oleracea is capable of developing an acid metabolism with many similarities to CAM. 相似文献
17.
Intact air-grown (photosynthetic photon flux density, 400 microeinsteins per square meter per second) clover plants ( Trifolium subterraneum L.) were transfered to high CO 2 (4000 microliters CO 2 per liter; photosynthetic photon flux density, 400 microeinsteins per square meter per second) or to high light (340 microliters CO 2 per liter; photosynthetic photon flux density, 800 microeinsteins per square meter per second) to similarly stimulate photosynthetic net CO 2 uptake. The daily increment of net CO 2 uptake declined transiently in high CO 2, but not in high light, below the values in air/standard light. After about 3 days in high CO 2, the daily increment of net CO 2 uptake increased but did not reach the high light values. Nightly CO 2 release increased immediately in high light, whereas there was a 3-day lag phase in high CO 2. During this time, starch accumulated to a high level, and leaf deterioration was observed only in high CO 2. After 12 days, starch was two- to threefold higher in high CO 2 than in high light, whereas sucrose was similar. Leaf carbohydrates were determined during the first and fourth day in high CO 2. Starch increased rapidly throughout the day. Early in the day, sucrose was low and similar in high CO 2 and ambient air (same light). Later, sucrose increased considerably in high CO 2. The findings that (a) much more photosynthetic carbon was partitioned into the leaf starch pool in high CO 2 than in high light, although net CO 2 uptake was similar, and that (b) rapid starch formation occurred in high CO 2 even when leaf sucrose was only slightly elevated suggest that low sink capacity was not the main constraint in high CO 2. It is proposed that carbon partitioning between starch (chloroplast) and sucrose (cytosol) was perturbed by high CO 2 because of the lack of photorespiration. Total phosphate pools were determined in leaves. Concentrations based on fresh weight of orthophosphate, soluble esterified phosphate, and total phosphate markedly declined during 13 days of exposure of the plants to high CO 2 but changed little in high light/ambient air. During this time, the ratio of orthophosphate to soluble esterified phosphate decreased considerably in high CO 2 and increased slightly in high light/ambient air. It appears that phosphate uptake and growth were similarly stimulated by high light, whereas the coordination was weak in high CO 2. 相似文献
18.
Photoautotrophic calli of Nicotiana plumbaginifolia were grown for 3 weeks under two CO 2 concentrations (500 and 20,000 microliters of CO 2 per liter). Calli cultured at high CO 2 exhibited a two-fold higher rate of growth. At CO 2 test levels, these calli were characterized by a lower net photosynthetic capacity than calli cultured at low CO 2. This diminution due to CO 2 adaptation could be ascribed to a 170% stimulation of dark respiration, a 40% decrease in total ribulose-1,5-bisphosphate carboxylase (Rubisco) activity, and also to a feedback inhibition of photosynthesis: high CO 2 grown calli contained about 5.5-fold more sucrose and three-fold less orthophosphate (Pi) than low CO 2 grown calli. Whether the decrease in Rubisco activity is related to the accumulation of sucrose and to the Pi limitation is discussed. Both calli exhibited a Warburg-effect showing the existence of active photorespiration at low CO 2. In calli grown at low CO 2 with 5 millimolar aminoacetonitrile (AAN), an inhibitor of the glycolate pathway, fresh weight decreased by 25% and chlorophyll content by 40%, dark respiration increased by 50% and net CO 2 uptake decreased by about 60% at 340 microliters of CO 2 per liter and 35% at 10,000 microliters of CO 2 per liter. In these calli, glutamine and glutamate contents were half of control calli. In contrast, AAN did not provoke any noticeable effect in calli grown at high CO 2. In photoautotrophic calli, the inhibition of the glycolate pathway by AAN results in severe perturbations in glutamate metabolism and in chlorophyll biosynthesis. 相似文献
19.
Carbon and nitrogen limitations on symbiotically grown soybean seedlings ( Glycine max [L.] Merr.) were assessed by providing 0.0, 1.0, or 8.0 millimolar NH 4NO 3 and 320 or 1,000 microliters CO 2/liter for 22 days after planting. Maximum development of the Rhizobium-soybean symbiosis, as determined by acetylene reduction, was measured in the presence of 1.0 millimolar NH 4NO 3 under both levels of CO 2. Raising NH 4NO 3 from 0.0 to 8.0 millimolar under 320 microliters CO 2/liter increased plant dry weight by 251% and Kjeldahl N content by 287% at 22 days after planting. Increasing NH 4NO 3 from 1.0 to 8.0 millimolar under 320 microliters CO 2/liter increased total dry weight and Kjeldahl N by 100 and 168%, respectively, on day 22. Raising CO 2 from 320 to 1,000 microliters CO 2/liter during the same period had no significant effect on Kjeldahl N content of plants grown with 0.0 or 1.0 millimolar NH 4NO 3. The maximum CO 2 treatment effects were observed in plants supplied with 8.0 millimolar NH 4NO 3, where dry weight and Kjeldahl N content were increased 64% and 20%, respectively. An increase in shoot CO 2-exchange rate associated with the CO 2-enrichment treatment was reflected in a significant increase in leaf dry weight and starch content for plants grown with 1,000 microliters CO 2/liter under all combined N treatments. These data show directly that seedling growth in symbiotically grown soybeans was limited primarily by N availability. The failure of the CO 2-enrichment treatment to increase total plant N significantly in Rhizobium-dependent plants indicates that root nodule development and functioning in such plants was not limited by photosynthate production. 相似文献
20.
One-year-old dormant white oak ( Quercus alba L.) seedlings were planted in a nutrient-deficient forest soil and grown for 40 weeks in growth chambers at ambient (362 microliters per liter) or elevated (690 microliters per liter) levels of CO 2. Although all of the seedlings became severely N deficient, CO 2 enrichment enhanced growth by 85%, with the greatest enhancement in root systems. The growth enhancement did not increase the total water use per plant, so water-use efficiency was significantly greater in elevated CO 2. Total uptake of N, S, and B was not affected by CO 2, therefore, tissue concentrations of these nutrients were significantly lower in elevated CO 2. An increase in nutrient-use efficiency with respect to N was apparent in that a greater proportion of the limited N pool in the CO 2-enriched plants was in fine roots and leaves. The uptake of other nutrients increased with CO 2 concentration, and P and K uptake increased in proportion to growth. Increased uptake of P by plants in elevated CO 2 may have been a result of greater proliferation of fine roots and associated mycorrhizae and rhizosphere bacteria stimulating P mineralization. The results demonstrate that a growth response to CO 2 enrichment is possible in nutrient-limited systems, and that the mechanisms of response may include either increased nutrient supply or decreased physiological demand. 相似文献
|