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1.
The possibility of altering CO 2 exchange of C 3-C 4 species by growing them under various CO 2 and O 2 concentrations was examined. Growth under CO 2 concentrations of 100, 350, and 750 micromoles per mole had no significant effect on CO 2 exchange characteristics or leaf anatomy of Flaveria pringlei (C 3), Flaveria floridana (C 3-C 4), or Flaveria trinervia (C 4). Carboxylation efficiency and CO 2 compensation concentrations in leaves of F. floridana developed under the different CO 2 concentrations were intermediate to F. pringlei and F. trinervia. When grown for 12 days at an O 2 concentration of 20 millimoles per mole, apparent photosynthesis was strongly inhibited in Panicum milioides (C 3-C 4) and to a lesser degree in Panicum laxum (C 3). In P. milioides, acute starch buildup was observed microscopically in both mesophyll and bundle sheath cells. Even after only 4 days exposure to 20 millimoles per mole O 2, the presence of starch was more pronounced in leaf cross-sections of P. milioides compared to those at 100 and 210 millimoles per mole. Even though this observation suggests that P. milioides has a different response to low O 2 with respect to translocation of photosynthate or sink activity than C 3 species, the concentration of total available carbohydrate increased in shoots of all species by 33% or more when grown at low O 2. This accumulation occurred even though relative growth rates of Festuca arundinacea (C 3) and P. milioides grown for 4 days at 210 millimoles per mole O 2, were inhibited 83 and 37%, respectively, when compared to plants grown at 20 millimoles per mole O 2. 相似文献
2.
A method based on the measurement of ATP/ADP ratios is described. It permits the determination of the critical respiratory oxygen pressure of any organ, or part of any organ, of an intact plant. The data obtained by this method with intact maize ( Zea mays L. INRA 508) root tips are compared with polarographic determinations on similar excised tissues. When internal O2 transport from the aerial part was prevented, the critical oxygen pressure found for the respiration of intact tips was similar to that found with excised tips. It was close to 10 kilopascals in a humid atmosphere and about 30 kilopascals in a liquid medium. Flooding of the gas spaces by vacuum infiltration did not modify these results. When internal O2 transport from the aerial parts of the plant occurred, significantly lower values were obtained in liquid medium for the critical oxygen pressure, which shifted from more than 21 to 6 kilopascals. The higher values observed with excised root tips, compared to those obtained with intact tissues, can be explained by the lack of internal O2 transport, rather than by the flooding of gas spaces. Data are presented which show that root growth started to be limited at a significantly higher pressure than the respiration. These results are attributed to nonrespiratory oxidative processes with a low affinity for O2 involved in root elongation. 相似文献
3.
When Frankia HFPCcI3 was grown in culture at oxygen O 2 levels ranging from 2 to 70 kilopascals O 2, under nitrogen fixing conditions, nitrogenase activity adapted to ambient pO 2 and showed a marked optimum close to growth pO 2. Vesicles were thin walled at low pO 2 and very thick walled at high pO 2. Freeze fracture transmission electron microscopy confirmed that Frankia produces vesicles with outer walls thickened by multiple lipid-like monolayers, in proportion to ambient pO 2. 相似文献
4.
Etiolated whole rice seedlings enclosed in sealed vials produced ethylene at a rate of 0.9 picomole per hour per seedling. When 2-centimeter-long shoots were subdivided into 5-millimeter-long sections, the sections containing the tip of the shoot evolved 37% of the total ethylene with the remaining 63% being produced along a gradient decreasing to the base of the shoot. The tip of the coleoptile also had the highest level of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and of the ethylene-forming enzyme activity. Ethylene is one of the factors controlling coleoptile elongation. Decapitation of the seedling reduced ethylene evolution to one-third its original level and inhibited coleoptile growth. In short-term experiments, the growth rate of decapitated seedlings was restored to almost that of intact seedlings by application of ethylene at a concentration of 10 microliters per liter. Apart from ethylene, O 2 also participates in the control of coleoptile growth. When rice seedlings were grown in a gas mixture of N 2 and O 2, the length of the coleoptiles reached a maximum at a concentration of 2.5% O 2. Lower and higher concentrations of O 2 reduced coleoptile growth. The effect of exogenous ethylene on coleoptile growth was also O 2 dependent. 相似文献
5.
Two cultivars of wheat ( Triticum aestivum L. cvs Sonoita and Yecora Rojo) were grown to maturity in a growth chamber within four sub-chambers under two CO 2 levels (350 or 1000 microliters per liter) at either ambient (21%) or low O 2 (5%). Growth analysis was used to characterize changes in plant carbon budgets imposed by the gas regimes. Large increases in leaf areas were seen in the low O 2 treatments, due primarily to a stimulation of tillering. Roots developed normally at 5% O 2. Seed development was inhibited by the subambient O 2 treatment, but this effect was overcome by CO 2 enrichment at 1000 microliters per liter. Dry matter accumulation and seed number responded differently to the gas treatments. The greatest dry matter production occurred in the low O 2, high CO 2 treatment, while the greatest seed production occurred in the ambient O 2, high CO 2 treatment. Growth and assimilation were stimulated more by either CO 2 enrichment or low O 2 in cv Yecora Rojo than in Sonoita. These experiments are the first to explore the effect of whole plant low O 2 treatments on growth and reproduction. The finding that CO 2 enrichment overcomes low O 2-induced sterility may help elucidate the nature of this effect. 相似文献
6.
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
7.
Soybean ( Glycine max cv Hodgson) nitrogenase activity (C 2H 2 reduction) in the presence or absence of nitrate was studied at various external O 2 tensions. Nitrogenase activity increased with oxygen partial pressure up to 30 kilopascals, which appeared to be the optimum. A parallel increase in ATP/ADP ratios indicated a limitation of respiration rate by low O 2 tensions in the nodule, and the values found for adenine nucleotide ratios suggested that the nitrogenase activity was limited by the rate of ATP regeneration. In the presence of nitrate, the nitrogenase activity was low and less stimulated by increased pO 2, although the nitrite content per gram of nodules decreased from 0.05 to 0.02 micromole when pO 2 increased from 10 to 30 kilopascals. Therefore, the accumulation of nitrite inside the nodule was probably not the major cause of the inhibition. Instead, inhibition by nitrate could be due to competition for reducing power between nitrate reduction and bacteroid or mitochondrial respiration inside the nodule. This is supported by the observation of decrease in ATP/ADP ratios from 1.65, in absence of nitrate, to 0.93 in the presence of this anion at 30 kilopascals O 2. Furthermore, the inhibition was suppressed by the addition, to the plant nutrient solution, of 15 millimolar l-malate, a carbon substrate that is considered to be the major source of reductant for the bacteroids in the symbiosis. 相似文献
8.
The effect of mechanical impedance on ethylene evolution and growth of preemergent maize ( Zea mays L.) seedlings was investigated by pressurizing the growth medium in triaxial cells in a controlled environment. Pressure increased the bulk density of the medium and thus the resistance to growth. The elongation of maize primary roots and preemergent shoots was severely hindered by applied pressures as low as 10 kilopascals. Following a steep decline in elongation at low pressures, both shoots and roots responded to additional pressure in a linear manner, but shoots were more severely affected than roots at higher pressures. Radial expansion was promoted in both organs by mechanical impedance. Primary roots typically became thinner during the experimental period when grown unimpeded. In contrast, pressures as low as 25 kilopascals caused a 25% increase in root tip diameter. Shoots showed a slight enhancement of radial expansion; however, in contrast to roots, the shoots increased in diameter even when growing unimpeded. Such morphological changes were not evident until at least 3 hours after initiation of treatment. All levels of applied pressure promoted ethylene evolution as early as 1 hour after application of pressure. After 1 hour, ethylene evolution rates had increased 10, 32, 70, and 255% at 25, 50, 75, and 100 kilopascals respectively, and continued to increase linearly for at least 10 hours. When intact corn seedlings were subjected to a series of hourly cycles of pressure, followed by relaxation, ethylene production rates increased or decreased rapidly, illustrating tight coupling between mechanical impedance and tissue response. Seedlings exposed to 1 microliter of ethylene per liter showed symptoms similar to those shown by plants grown under mechanical impedance. Root diameter increased 5 times as much as the shoot diameter. Pretreatment with 10 micromolar aminoethoxyvinyl glycine plus 1 micromolar silver thiosulfate maintained ethylene production rates of impeded seedlings at basal levels and restored shoot and root extension to 84 and 90% of unimpeded values, respectively. Our results support the hypothesis that ethylene plays a pivotal role in the regulation of plant tissue response to mechanical impedance. 相似文献
9.
A plant was found in the C 3-C 4 intermediate species, Flaveria linearis, in which apparent photosynthesis is stimulated by atmospheric O 2 concentrations. A survey of 44 selfed progeny of the plant showed that the O 2 stimulation of apparent photosynthesis was passed on to the progeny. When leaves equilibrated at 210 milliliters per liter O 2 were transferred to 20 milliliters per liter O 2 apparent photosynthesis was initially stimulated, but gradually declined so that at 30 to 40 minutes the rate was only about 80 to 85% of that at 210 milliliters per liter O 2. Switching from 20 to 210 milliliters per liter caused the opposite transition in apparent photosynthesis. All other plants of F. linearis reached steady rates within 5 minutes after switching O 2 that were 20 to 24% lower in 210 than in 20 milliliters per liter O 2. At low intercellular CO 2 concentrations and low irradiances, O 2 inhibition of apparent photosynthesis of the aberrant plant was similar to that in normal plants, but at an irradiance of 2 millimoles quanta per square meter per second and near 300 microliters per liter CO 2 apparent photosynthesis was consistently higher at 210 than at 20 milliliters per liter O 2. In morphology and leaf anatomy, the aberrant plant is like the normal plants in F. linearis. The stimulation of apparent photosynthesis at air levels of O 2 in the aberrant plant is similar to other literature reports on observations with C 3 plants at high CO 2 concentrations, high irradiance and/or low temperatures, and may be related to limitation of photosynthesis by triose phosphate utilization. 相似文献
10.
A fiber optic spectrophotometric system was used to monitor the in vivo oxygenation of leghemoglobin in intact, attached soybean root nodules ( Glycine max L. Merr. × USDA 16 Bradyrhizobium japonicum) which were flattened during development by growth in narrow, glass-walled cuvettes. When equilibrated at an external pO 2 of 20 kilopascals, leghemoglobin was 36.6 ± 5.4% oxygenated, a value estimated to represent an infected cell O 2 concentration of 21.5 nanomolar. Increasing the external pO 2 from 20 to 25 kilopascals caused a rapid increase in leghemoglobin oxygenation, followed by a recovery to the initial level, all within 7.5 minutes. At 25 kilopascals O 2, the rates of H 2 and CO 2 evolution were similar to those at 20 kilopascals. Since respiration had not increased, the results support the proposal that nodules adapt to increased external pO 2 by regulating their resistance to O 2 diffusion. 相似文献
11.
Partitioning of 14C was assessed in sweet chestnut seedlings ( Castanea sativa Mill.) grown in ambient and elevated atmospheric [CO 2] environments during two vegetative cycles. The seedlings were exposed to 14CO 2 atmosphere in both high and low [CO 2] environments for a 6-day pulse period under controlled laboratory conditions. Six days after exposure to 14CO 2, the plants were harvested, their dry mass and the radioactivity were evaluated. 14C concentration in plant tissues, root-soil system respiratory outputs and soil residues (rhizodeposition) were measured. Root production and rhizodeposition were increased in plants growing in elevated atmospheric [CO 2]. When measuring total respiration, i.e. CO 2 released from the root/soil system, it is difficult to separate CO 2 originating from roots and that coming from the rhizospheric microflora. For this reason a model accounting for kinetics of exudate mineralization was used to estimate respiration of rhizospheric microflora and roots separately. Root activity (respiration and exudation) was increased at the higher atmospheric CO 2 concentration. The proportion attributed to root respiration accounted for 70 to 90% of the total respiration. Microbial respiration was related to the amount of organic carbon available in the rhizosphere and showed a seasonal variation dependent upon the balance of root exudation and respiration. The increased carbon assimilated by plants grown under elevated atmospheric [CO 2] stayed equally distributed between these increased root activities. ei]H Lambers 相似文献
12.
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
13.
Spinach ( Spinacia oleracea var “Yates”) plants in hydroponic culture were exposed to stepwise increased concentrations of NaCl or NaNO 3 up to a final concentration of 300 millimoles per liter, at constant Ca 2+-concentration. Leaf cell sap and extracts from aqueously isolated spinach chloroplasts were analyzed for mineral cations, anions, amino acids, sugars, and quarternary ammonium compounds. Total osmolality of leaf sap and photosynthetic capacity of leaves were also measured. For comparison, leaf sap from salt-treated pea plants was also analyzed. Spinach plants under NaCl or NaNO 3 salinity took up large amounts of sodium (up to 400 millimoles per liter); nitrate as the accompanying anion was taken up less (up to 90 millimoles per liter) than chloride (up to 450 millimoles per liter). Under chloride salinity, nitrate content in leaves decreased drastically, but total amino acid concentrations remained constant. This response was much more pronounced (and occurred at lower salt concentrations) in leaves from the glycophyte (pea, Pisum sativum var “Kleine Rheinländerin”) than from moderately salt-tolerant spinach. In spinach, sodium chloride or nitrate taken up into leaves was largely sequestered in the vacuoles; both salts induced synthesis of quarternary ammonium compounds, which were accumulated mainly in chloroplasts (and cytosol). This prevented impairment of metabolism, as indicated by an unchanged photosynthetic capacity of leaves. 相似文献
14.
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
15.
Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weight, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L.) Heynh. (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2·5, 5·1, 10·1, 16·2, and 21·3 kPa O 2, 0·035 kPa CO 2 and the balance nitrogen under continuous light. Fully expanded leaves were harvested and processed for light and transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been described for plants grown under carbon dioxide enrichment. However, at the lowest oxygen treatment (2·5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespiration, resulting in very thick leaves and a dwarf morphology. This study establishes the leaf parameters that change during growth under low O 2, and identifies the lower concentration at which O 2 limitation on transport and biosynthetic pathways detrimentally affects leaf development. 相似文献
16.
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
17.
Seedlings of Schima superba were exposed to both ambient (375 ppm) and 720 ppm levels of CO 2 in combination with two incubation temperatures (25/20, 30/25°C, day/night) for a six-month period. Net height growth of seedlings was enhanced in the early period of exposure to high levels of CO 2. However, when seedlings were exposed for a longer period of time to this high concentration, net height growth was inhibited. Decreased photosynthetic rate with elevated CO 2 was observed when measured in the ambient CO 2 over a long-term exposure of 6 months. In contrast, a significant increase in photosynthesis was noted for seedlings exposed to higher incubation temperature in either ambient or 720 ppm CO 2 concentrations. The response of CO 2 assimilation to internal Ci was indicated by the lower sensitivity in seedlings grown in elevated CO 2 concentration. Though this response could also be found in a higher sensitivity in seedlings grown at higher temperature, the seedlings grown in normal conditions (ambient CO 2 and temperature) were still more sensitive to CO 2 assimilation response to internal Ci. This experiment suggests that: (1) exposure of seedlings to higher CO 2 levels for longer periods may lead to a decrease in seedling height growth and photosynthetic rate, as well as decreasing sensitivity to changing internal CO 2 concentrations; (2) the optimum temperature for photosynthesis of seedlings grown in an elevated CO 2 concentration was higher than that for seedlings grown in ambient concentration. 相似文献
18.
Sugar maple ( Acer saccharum Marsh.) seedlings were grown in a nursery for three years in 13, 25, 45 and 100 per cent of full daylight. During the third year of growth, the rates of their apparent photosynthesis and respiration were measured periodically with an infra-red gas analyzer at various light intensities and normal CO 2 concentration. In addition, the rates of apparent photosynthesis of a single attached leaf of the same seedlings were measured at saturating light intensity, hut varying CO 2 concentrations. An increase in the light intensity in which seedlings were grown had no effect on their height or mean leaf area, hut resulted in thicker leaves, an increase in the total leaf area per seedling due to an increase in the number of leaves, an increase in the dry weight especially of roots and a decrease in the chlorophyll content of leaves. Throughout the growing season seedlings grown in full daylight, as compared with those grown in lower light intensities, had the lowest rates of apparent photosynthesis measured at standard conditions (21,600 lux light intensity and 300 ul/l of CO 2), when this was expressed per unit leaf area, hut the highest rates on a per seedling basis. Thus dry matter production attained at the end of the growing season correlated positively with the photosynthetic rate per seedling, but not per unit leaf area. The rates of apparent photosynthesis of seedlings grown at lower light intensities were more responsive to changes in light intensity or CO 2 concentration than those of seedlings grown in full daylight intensity. 相似文献
19.
Naturally occurring high levels of ethylene can be a problem in spaceflight and controlled environment agriculture (CEA) leading to sterility and irregular plant growth. There are engineering and safety advantages of growing plants under hypobaria (low pressure) for space habitation. The goals of this research were to successfully grow lettuce ( Lactuca sativa cv. Buttercrunch) in a long-term study from seed to harvest under hypobaric conditions, and to investigate how endogenously produced ethylene affects gas exchange and plant growth from seed germination to harvest under hypobaric and ambient total pressure conditions. Lettuce was grown under two levels of total gas pressure [hypobaric or ambient (25 or 101 kPa)] in a long-term, 32-day study. Significant levels of endogenous ethylene occurred by day-15 causing reductions in photosynthesis, dark-period respiration, and a subsequent decrease in plant growth. Hypobaria did not mitigate the adverse ethylene effects on plant growth. Seed germination was not adversely affected by hypobaria, but was reduced by hypoxia (6 kPa pO 2). Under hypoxia, seed germination was higher under hypobaria than ambient total pressure. This research shows that lettuce can be grown from seed to harvest under hypobaria (≅25% of normal earth ambient total pressure). 相似文献
20.
The supply of heterotrophically growing suspensions of Alcaligenes eutrophus PHB ?4 with oxygen formed by the continuous addition of H 2O 2 in the presence of bovine liver catalase was found to be restricted to well-defined conditions. The catalase-H 2O 2 system proved to be suitable during the growth at low cell densities equivalent to 2 g dry weight/liter. When under these conditions the oxygen concentration was held constant at 1.8 mg O 2/liter, the cells grew for 6–8 hr at a rate almost identical to that observed with conventional aeration. However, aeration with H 2O 2 for longer durations (10–20 hr) and at higher cell densities (5?20 g dry weight/liter) led invariably to cell damage and retardation of growth. The impairment of growth observed during the oxygen supply by the catalase?H 2O 2 system was traced back to the formation of gradually increasing steady-state concentrations of H 2O 2 in the medium. Possible sites of cell damage by H 2O 2 such as membrane function, excretion and function of siderophores, and synthesis of cell polymers have been studied, and the cytotoxic mechanism of low concentrations of H 2O 2 was discussed. 相似文献
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