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1.
A system has been developed for the isolation of photosynthetically active chloroplasts from leaves of Populus deltoides. A high proportion of the chloroplasts appeared intact. The maximum rates of different photosynthetic processes were as follows: CO 2 fixation 3.5 micromoles per milligram chlorophyll per hour, noncyclic ATP synthesis 10 micromoles per milligram chlorophyll per hour, and cyclic ATP synthesis 300 micromoles per milligram chlorophyll per hour. 相似文献
2.
The fruticose thallus of the lichen Cladina stellaris (Opiz.) Brodo can be subdivided into individual whorls of branches of known age. Photosynthesis declines steadily with age from a maximum rate of 0.76 milligram CO 2 per gram dry weight per hour in 1-year-old whorls to 0.02 milligram CO 2 per gram dry weight per hour after 15 years. Conversely, the dry biomass of the whorls increases up to age 9 years and then approximately levels off. Photosynthesis in whorls older than 15 years is less than 0.01 milligram per gram per hour. Progressive changes in thallus color with age are associated with the observed photosynthetic decline. Whorls aged 6 years and younger together account for 18% of thallus biomass but 50% of photosynthetic activity. The implications of these results for the idea that the lichen symbiosis results in truly integrated organisms with senescence phenomena akin to those in higher plants is discussed. 相似文献
3.
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
4.
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
5.
Haploid callus cells of tobacco ( Nicotiana tabacum) were grown photoautotrophically on a solid agar medium in the absence of sucrose in Petri plates in an atmosphere of 1% or 3% CO 2 in air. The averages of dry weight increases for four to five consecutive passages were 2.3- to 3.6-fold per 3-week passage for different subclones. Photosynthetic 14CO 2 assimilation was maximum at about 1% CO 2 with half-maximal rates obtained at 0.2% CO 2. At saturating CO 2 concentration the average rate of CO 2 fixation was about 5 μmole per gram fresh weight per hour or about 125 μmole per mg of chlorophyll per hour. 相似文献
6.
The photosynthetic rates in two psychrophilic diatoms, Chaetoceros sp. strain K3-10 and Nitzschia sp. K3-3 for cells grown at 0°C were 8 to 10 microliters O 2 evolved per milligram dry weight per hour, and 10-fold higher, about 80 for cells grown at 10°C. The respiration rates followed the same pattern, with a value of around 1 microliter dark uptake per milligram dry weight per hour for both organisms grown at 0°C, and 6 to 10 for cells grown at 10°C. When cells grown at 0°C were immediately shifted to 10°C or cells grown at 10°C were shifted to 0°C, the respiratory rates quickly adapted to values characteristic of cells grown at the shift temperature. On the other hand, the light-saturated rate of O 2 evolution showed much less immediate adaptation, especially on the up shift, 0° to 10°C. The chlorophyll a content of 0°C grown cells was about 0.5% of dry weight, in 10°C grown cells 1.3% (strain K3-10) and 2.2% (strain K3-3). In addition to a diminished chlorophyll a content in 0°C grown cells, there seemed proportionally (by absorbance and calculation) less c to a than in 10°C grown cells. The relative fluorescence excitation spectra of 680-nm emission also showed a lower contribution by both chlorophyll c and fucoxanthin in 0°C grown cells of Chaetoceros sp. strain K3-10 as compared to 10°C grown cells. The data at hand suggest that in psychrophilic diatoms continuously growing at 0°C there may be problems associated with synthesis of an effective accessory pigment system, and as a working hypothesis it is suggested this is related to restriction of synthesis of one or several accessory pigment proteins. 相似文献
7.
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
8.
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
9.
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
10.
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
11.
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
12.
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
13.
The reductive carboxylic acid cycle, the autotrophic pathway of CO 2 assimilation in prokaryotes (photosynthetic and nonphotosynthetic autotrophic bacteria), was investigated in Chlamydomonas reinhardtii F-60, an algal mutant lacking a complete photosynthetic carbon reduction pathway (C 3) due to a deficiency in phosphoribulokinase. Evidence was obtained consistent with the presence of the reductive carboxylic acid cycle in F-60. This conclusion is based on the fact that: (a) acetate approximately doubled CO 2 fixation in whole cells (4 micromoles per milligram chlorophyll per hour) and in chloroplasts (32 nanomoles per milligram chlorophyll per hour); and (b) pyruvate synthase, α-ketoglutarate synthase, and ATP-citrate lyase, three indicators of the cycle, were found in cell-free extracts. 相似文献
14.
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
15.
Chloroplasts have been isolated from 4- to 6-day-old corn ( Zea mays) leaves capable of assimilating 45 micromoles CO 2 per milligram chlorophyll per hour. The effects of various factors such as inorganic phosphate, reducing agents, inhibitors, intermediates of the photosynthetic carbon reduction cycle, organic acids, and oxygen on the photosynthetic rate and on the distribution of 14C within the products by these chloroplasts were determined. The photosynthetic carbon metabolism of the corn plastids appeared to be similar to that already observed in spinach and pea chloroplasts. It was concluded that the corn plastids can fix CO 2 at meaningful rates via the photosynthetic carbon reduction cycle of Calvin without the operation of a cycle involving the C-4 compounds, malate and aspartate. 相似文献
16.
Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon chmielewskii Rick, LA 1028, were exposed to two CO 2 concentrations (330 or 900 microliters per liter) for 10 weeks. Tomato plants grown at 900 microliters per liter contained more starch and more sugars than the control. However, we found no significant accumulation of starch and sugars in the young leaves of L. esculentum exposed to high CO 2. Carbon exchange rates were significantly higher in CO 2-enriched plants for the first few weeks of treatment but thereafter decreased as tomato plants acclimated to high atmospheric CO 2. This indicates that the long-term decline of photosynthetic efficiency of leaf 5 cannot be attributed to an accumulation of sugar and/or starch. The average concentration of starch in leaves 5 and 9 was always higher in L. esculentum than in L. chmielewskii (151.7% higher). A higher proportion of photosynthates was directed into starch for L. esculentum than for L. chmielewskii. However, these characteristics did not improve the long-term photosynthetic efficiency of L. chmielewskii grown at high CO 2 when compared with L. esculentum. The chloroplasts of tomato plants exposed to the higher CO 2 concentration exhibited a marked accumulation of starch. The results reported here suggest that starch and/or sugar accumulation under high CO 2 cannot entirely explain the loss of photosynthetic efficiency of high CO 2-grown plants. 相似文献
17.
Young expanding spinach leaves exposed to 14CO 2 under physiological conditions for up to 20 minutes assimilated CO 2 into lipids at a mean rate of 7.6 micromoles per milligram chlorophyll per hour following a lag period of 5 minutes. Label entered into all parts of the lipid molecule and only 28% of the 14C fixed into lipids was found in the fatty acid moieties, i.e. fatty acids were synthesized from CO 2in vivo at a mean rate of 2.1 micromoles per milligram chlorophyll per hour. Intact spinach chloroplasts isolated from these leaves incorporated H 14CO 3 into fatty acids at a maximal rate of 0.6 micromole per milligram chlorophyll per hour, but were unable to synthesize either the polar moieties of their lipids or polyunsaturated fatty acids. Since isolated chloroplasts will only synthesize fatty acids at rates similar to the one obtained with intact leaves in vivo if acetate is used as a precursor, it is suggested that acetate derived from leaf mitochondria is the physiological fatty acid precursor. 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.
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
20.
Chloroplasts isolated from Kalanchoe diagremontiana leaves were capable of photosynthesizing at a rate of 5.4 μmoles of CO 2 per milligram of chlorophyll per hour. The dark rate of fixation was about 1% of the light rate. A high photosynthetic rate was associated with low starch content of the leaves. Ribose 5-phosphate, fructose 1,6-diphosphate, and dithiothreitol stimulated fixation, whereas phosphoenolpyruvate and azide were inhibitors. The products of CO 2 fixation were primarily those of the photosynthetic carbon reduction cycle. 相似文献
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