共查询到20条相似文献,搜索用时 46 毫秒
1.
The influence of light or darkness on stomatal opening in epidermal strips of Commelina benghalensis was evaluated in the presence or absence of O 2 and/or metabolic inhibitors. Opening was restricted in nitrogen and was promoted by NADH and acids of the tricarboxylic acid cycle (succinate and α-ketoglutarate) in CO 2-free air in light as well as in darkness. The enhancement by light of stomatal opening was prevalent under nitrogen or in the presence of the respiratory inhibitors (sodium azide and oligomycin). Respiratory inhibitors decreased the opening in light or darkness under CO 2-free air but exhibited no effect under nitrogen, whereas phosphorylation uncouplers were inhibitory in light or darkness under both CO 2-free air and nitrogen. The results suggest that oxidative phosphorylation is a basic source of energy for stomatal opening, although photophosphorylation could be an energy source. 相似文献
2.
Using an open and a closed system of gas analysis, it was found that CO 2 evolution in light and in darkness from plant leaves (sunflower, soybean, watermelon, eggplant, and jackbean) have a different response to temperature. While the rate of CO 2 evolution in light increased with increasing temperature from 17 to 35° and then declined, the rate of CO 2 evolution in darkness increased continuously up to 40°. The rate of CO 2 evolution in light was affected by light intensity. At 1800 ft-c and below 35° the rate of CO 2 evolution in light was greater than in darkness, but above 35° it became lower than in darkness. The Q 10 for CO 2 evolution in light was consistently lower than that in darkness. 相似文献
3.
Photosynthetic carboxylating enzymes and the effects of light and temperature on 14CO 2 efflux in two species of gymnosperm leaves were studied. The activity of RuBP carboxylase was high and that of PEP carboxylase was very low when compared to C 4 plants. The CO 2 compensation point was high. 14CO 2 efflux was greater in light than in darkness and the ratio (L/D) increased with increase in temperature and light intensity. The inhibitors of glycolate metabolism showed decreased 14CO 2 evolution in light while dark respiration was unaffected. It is concluded that both Cycas circinalis, L. and Cycas beddomei Dyer are C 3 plants. 相似文献
4.
The metabolism of 14C-glycine (a substrate for photorespiration) was studied in the light and in darkness under natural CO 2 concentration (0.03%) in the leaves of ephemeroides Scilla sibirica Haw. and Ficaria verna Huds. at different developmental stages. Using one and the same sample, potential photosynthesis (at 1% CO 2), true photosynthesis (at 0.03% CO 2), and leaf respiratory capacity were measured by the radiometric and manometric methods, respectively. All measurements were performed at 15°C, an average temperature during ephemer growth. It was found that, in the white zone of the Scilla leaf, the rate of CO 2 evolution resulting from metabolization of exogenous 14C-glycine was similar in the light and in darkness. In the green zone of the Scilla leaf and in the green leaf of Ficaria, both 14C-glycine absorption and 14CO 2 evolution were lower in the light as compared with darkness, which is explained by CO 2 reassimilation. In all treatments of both plant species, a specific inhibitor of glycine decarboxylase complex (GDC), aminoacetonitrile (5 mM) suppressed CO 2 evolution by 20–40%. It was concluded that in ephemeroides mitochondrial GDC, responsible for CO 2 evolution in photorespiration, is formed at the earliest stage of leaf development. This indicates that photorespiration can occur simultaneously with the development of the leaf photosynthetic activity. On the basis of the assumption that carbon losses in the form of CO 2 evolved during photorespiration comprise 25% of true photosynthesis, it was calculated that, in ephemer leaves, the highest rates of photorespiration and photosynthesis were attained during flowering when the leaf area was the largest and the rate of dark respiration was reduced by 1.5–2.0 times. The highest rates of dark respiration were observed in the beginning of growth. In senescing leaves by the end of the plant vegetation, potential photosynthesis and true photosynthesis were reduced, whereas dark respiration remained essentially unchanged. It is concluded that the high rates of potential and true photosynthesis are characteristic of ephemeroides when they complete their short developmental program in early spring (at 15°C); theoretically, photorespiration also occurs at a high rate during this period, when this process provides for a defense against the threat of photoinhibition at low temperature and high insolation. 相似文献
5.
A mass spectrometric method combining 16O/ 18O and 12C/ 13C isotopes was used to quantify the unidirectional fluxes of O 2 and CO 2 during a dark to light transition for guard cell protoplasts and mesophyll cell protoplasts of Commelina communis L. In darkness, O 2 uptake and CO 2 evolution were similar on a protein basis. Under light, guard cell protoplasts evolved O 2 (61 micromoles of O 2 per milligram of chlorophyll per hour) almost at the same rate as mesophyll cell protoplasts (73 micromoles of O 2 per milligram of chlorophyll per hour). However, carbon assimilation was totally different. In contrast with mesophyll cell protoplasts, guard cell protoplasts were able to fix CO 2 in darkness at a rate of 27 micromoles of CO 2 per milligram of chlorophyll per hour, which was increased by 50% in light. At the onset of light, a delay observed for guard cell protoplasts between O 2 evolution and CO 2 fixation and a time lag before the rate of saturation suggested a carbon metabolism based on phospho enolpyruvate carboxylase activity. Under light, CO 2 evolution by guard cell protoplasts was sharply decreased (37%), while O 2 uptake was slowly inhibited (14%). A control of mitochondrial activity by guard cell chloroplasts under light via redox equivalents and ATP transfer in the cytosol is discussed. From this study on protoplasts, we conclude that the energy produced at the chloroplast level under light is not totally used for CO 2 assimilation and may be dissipated for other purposes such as ion uptake. 相似文献
6.
The total metabolic cost of soybean ( Glycine max L. Mer Clark) nodule nitrogen fixation was empirically separated into respiration associated with electron flow through nitrogenase and respiration associated with maintenance of nodule function. Rates of CO2 evolution and H2 evolution from intact, nodulated root systems under Ar:O2 atmospheres decreased in parallel when plants were maintained in an extended dark period. While H2 evolution approached zero after 36 hours of darkness at 22°C, CO2 evolution rate remained at 38° of the rate measured in light. Of the remaining CO2 evolution, 62% was estimated to originate from the nodules and represents a measure of nodule maintenance respiration. The nodule maintenance requirement was temperature dependent and was estimated at 79 and 137 micromoles CO2 (per gram dry weight nodule) per hour at 22°C and 30°C, respectively. The cost of N2 fixation in terms of CO2 evolved per electron pair utilized by nitrogenase was estimated from the slope of H2 evolution rate versus CO2 evolution rate. The cost was 2 moles CO2 evolved per mole H2 evolved and was independent of temperature. In this symbiosis, nodule maintenance consumed 22% of total respiratory energy while the functioning of nitrogenase consumed a further 52%. The remaining respiratory energy was calculated to be associated with ammonia assimilation, transport of reduced N, and H2 evolution. 相似文献
7.
The CO 2 exchange of several species of fresh water and marine algae was measured in the laboratory to determine whether photorespiration occurs in these organisms. The algae were positioned as thin layers on filter paper and the CO 2 exchange determined in an open gas exchange system. In either 21 or 1% O 2 there was little difference between 14CO 2 and 12CO 2 uptake. Apparent photosynthesis was the same in 2, 21, or 50% O 2. The compensation points of all algae were less than 10 μl 1 −1. CO 2 or 14CO 2 evolution into CO 2-free air in the light was always less than the corresponding evolution in darkness. These observations are inconsistent with the proposal that photorespiration exists in these algae. 相似文献
8.
In air largely freed from CO 2, senescence of isolated oat ( Avena sativa cv Victory) seedling leaves is no longer prevented by white light; instead, the leaves lose both chlorophyll and protein as rapidly as in the dark. Senescence in light is also accelerated in pure O 2, but it is greatly delayed in N 2; 100% N 2 preserves both protein and chlorophyll in light and in darkness. In light in air, most of the compounds tested that had previously been found to delay or inhibit senescence in darkness actually promote the loss of chlorophyll, but they do not promote proteolysis. Under these conditions, proteolysis can therefore be separated from chlorophyll loss. But in light minus CO 2, where chlorophyll loss is rapid in controls, two of these same reagents prevent the chlorophyll loss. Unlike the many reagents whose action in light is thus the opposite of that in darkness, abscisic acid, which promotes chlorophyll loss in the dark, also promotes it in light with or without CO 2. Kinetin, which prevents chlorophyll loss in the dark, also prevents it in light minus CO 2. In general, therefore, the responses to light minus CO 2 are similar to the responses to darkness, and (with the exception of abscisic acid and kinetin) opposite to the response to light in air. 相似文献
9.
Dark grown wheat leaves ( Triticum aestivum L. cv. Starke II Weibull), treated with δ-aminolevulinic acid in darkness, showed an increased oxygen uptake as measured by a Warburg method. The production of CO 2 was also increased in darkness, giving an RQ ? 1. The increased respiration was dependent on the treatment time as well as on the concentration of the δ-aminolevulinic acid. Potassium cyanide suppressed both the normal and the increased respiration. The treatment with δ-aminolevulinic acid caused accumulation of high amounts of protochlorophyllide. Levulinic acid suppressed the increased oxygen uptake as well as the protochlorophyllide accumulation in δ-aminolevulinic acid treated leaves. Irradiation rapidly decreased the protochlorophyllide content with a simultaneous increase in oxygen uptake over the dark value. The peak value of the increase in oxygen uptake was reached after about 5 min. The light induced oxygen uptake was dependent on the amount of PChlide present at the onset of irradiation. Also the CO 2 production was increased during the first minutes of irradiation but soon fell under the buffer control value. Neither potassium cyanide nor heat denaturation affected the oxygen uptake in light in contrast to the effect on the CO 2 production, which was blocked by heat denaturation. The increased oxygen uptake in light initially seems to be a purely photochemical process leading to a release of CO 2, which release is probably an enzymatic process induced by the photo-oxidative decomposition of pigment. 相似文献
10.
In light and in darkness, exposure of leaf segments to CO 2-free atmospheres caused a marked reduction in extractable RuBP carboxylase activity. By contrast, darkness caused a relatively small decrease in carboxylase activity in extracts from leaf segments kept in air containing CO 2. Recovery of carboxylase activity in leaves during illumination in air after exposure to CO 2-free conditions paralleled recovery of capacity for photosynthesis; in darkness recovery of carboxylase activity in leaves was slower than in the light. Extracts from leaves exposed to CO 2-free conditions recovered activity when provided with CO 2 and Mg 2+; there were clearly, however, substances in the extracts that modified the activity achieved and caused anomalous decreases and increases with time after extraction. Studies of the effect of orthophosphate on the activity of purified wheat carboxylase in vitro were consistent with the view that many of the effects observed on the activity of crude leaf extracts were due to orthophosphate content. 相似文献
11.
The effect of oxygen concentration on the rate of CO 2-uptake in continuous and intermittent light was studied as well as the CO 2-fixation during a short dark period after light was turned off. In addition the dark respiration and the CO 2-compensation point of attached and detached corn leaves were determined. Leaves of 4 to 22-day old plants were used as experimental material. A closed circuit system of an infrared carbon dioxide analyzer was employed to measure the rate of CO 2-exchange. It was found that in an atmosphere consisting of 100 % oxygen, there was about 50 per cent inhibition of the rate of CO 2-uptake in continuous and intermittent light compared to that in an atmosphere consisting of 21% oxygen. The same was true of the rate of CO 2-fixation in darkness during a short period after the light was turned off. Since the response to oxygen concentration of the CO 2-uptake in light and of the CO 2-fixation in darkness after the light was turned off were similar, it is concluded that the fixation of CO 2 in the short dark period represents an over- shoot of photosynthesis. The rate of dark respiration was little affected by the oxygen concentration in the ranges used in the experiments. The carbon dioxide compensation point which has been observed in leaves of 4 to 14-day old plants was not influenced by either oxygen concentration or light intensity. Since the changes in the rate of CO 2-uptake due to changes in the concentration of oxygen and light intensity had no effect on the CO 2-compensation point, it is concluded that a reabsorption of respiratory CO 2 by photosynthesis could not account for the low value of this point. These results are interpreted as a further corroboration of the statement that the leaves of corn lack the process of photorespiration and that dark respiration is inhibited in light. It was observed that the rate of the CO 2-uptake gradually increased in plants which were from 4 to 22-days old. The inhibitory effect of high concentration of oxygen on the rate of CO 2-uptake was relatively higher in old plants than in young ones. 相似文献
12.
Summary CO 2 exchange and air flow through the stomata were measured in leaf sections of Zea mays at temperatures between 7 and 52° and under optimal water supply. The results were summarized in polynomials fitted to the data.In leaf samples brought from 16° and darkness into different experimental temperatures and light, CO 2 assimilation has a maximum near 30°. Above 37° (in other experiments above 41°), net CO 2 uptake stops abruptly and is replaced by CO 2 evolution in light. If a 1-hr treatment with 25° and light is inserted between darkness and the experimental temperatures, the threshold above which the assimilatory system collapses shifts 3 degrees upwards, to 40° (or 44°); the decline of CO 2 assimilation with high temperatures is less steep than without pretreatment; and the upper compensation point moves upscale by as much as 5 degrees.Stomatal conductance for CO 2 does not, in general, follow an optimum curve with temperature. Between 15 and 35° it is approximately proportional to net CO 2 assimilation, indicating control by CO 2; but above 35°, stomatal aperture increases further with temperature (and so does stomatal variability): the stomata escape the control by CO 2 and above 40° may be wide open even if CO 2 is being evolved. Stomatal conductance for CO 2 below 15° may also be larger than would be proportional to CO 2 assimilation.Net CO 2 assimilation and stomatal conductance at 25° were reduced if the leaf samples were pretreated with temperatures below approximately 20° and above 30°. Stomata were more sensitive to past temperatures than was CO 2 assimilation. 相似文献
13.
Efflux of carbon dioxide in light and darkness was measured at low ambient CO 2 concentrations in leaves of Rumex acetosa. Light carbon dioxide production (photo-respiration) was found to depend on irradiance and to differ from dark production as to the response to temperature and ambient concentrations of O 2 and CO 2. These observations support previously made suggestions that photorespiration follows a different metabolic pathway to dark respiration. 相似文献
14.
The photosynthetic properties of the internal and peripheral tissues of the cherry tomato fruit ( Lycopersicum esculentum var. cerasiforme Dun A. Gray) were investigated. Whole fruit and their isolated tissues evolve large amounts of CO 2 in darkness. In the light, this evolution decreases but nevertheless remains a net evolution; 3-(3,4-dichlorophenyl)-1,1-dimethylurea abolishes the effects of light. 相似文献
15.
The freshwater microalga, Chlamydomonas reinhardtii Dangeard, was cultured under 350 and 700 ppmv CO 2 to determine the impact of doubled atmospheric CO 2 concentration on its growth and photosynthesis. No significant difference was observed in the specific growth rate, photosynthetic efficiency, maximal net photo‐synthetic rate and light‐saturating point between the low and high CO 2 cultures. Both the low‐ and high‐CO 2‐grown cells showed reduced light‐dependent O 2 evolution rate and photochemical efficiency ( Fv/ Fm) owing to photoinhibition when exposed to high photon flux density. However, high‐CO 2‐grown cells were less photoinhibited, and showed better recovery in dim light or darkness during the initial period of the recovery process. 相似文献
16.
- C4 plants supply concentrated CO2 to bundle sheath (BS) cells, improving photosynthetic efficiency by suppressing photorespiration. Mesophyll chloroplasts in C4 plants are redistributed toward the sides of the BS cells (aggregative movement) in response to environmental stresses under light. Although this chloroplast movement is common in C4 plants, the significance and mechanisms underlying the aggregative movement remain unknown.
- Under environmental stresses, such as drought and salt, CO2 uptake from the atmosphere is suppressed by closing stomata to prevent water loss. We hypothesized that CO2 limitation may induce the chloroplast aggregative movement. In this study, the mesophyll chloroplast arrangement in a leaf of finger millet, an NAD-malic enzyme type C4 plant, was examined under different CO2 concentrations and light conditions.
- CO2 limitation around the leaves promoted the aggregative movement, but the aggregative movement was not suppressed, even at the higher CO2 concentration than in the atmosphere, under high intensity blue light. In addition, mesophyll chloroplasts did not change their arrangement under darkness or red light.
- From these results, it can be concluded that CO2 limitation is not a direct inducer of the aggregative movement but would be a promoting factor of the movement under high intensity blue light.
相似文献
17.
Leaf photosynthesis of the sensitive plant Mimosa pudica displays a transient knockout in response to electrical signals induced by heat stimulation. This study aims at clarifying the underlying mechanisms, in particular, the involvement of respiration. To this end, leaf gas exchange and light reactions of photosynthesis were assessed under atmospheric conditions largely eliminating photorespiration by either elevated atmospheric CO 2 or lowered O 2 concentration (i.e. 2000 μmol mol ?1 or 1%, respectively). In addition, leaf gas exchange was studied in the absence of light. Under darkness, heat stimulation caused a transient increase of respiratory CO 2 release simultaneously with stomatal opening, hence reflecting direct involvement of respiratory stimulation in the drop of the net CO 2 uptake rate. However, persistence of the transient decline in net CO 2 uptake rate under illumination and elevated CO 2 or 1% O 2 makes it unlikely that photorespiration is the metabolic origin of the respiratory CO 2 release. In conclusion, the transient knockout of net CO 2 uptake is at least partially attributed to an increased CO 2 release through mitochondrial respiration as stimulated by electrical signals. Putative CO 2 limitation of Rubisco due to decreased activity of carbonic anhydrase was ruled out as the photosynthesis effect was not prevented by elevated CO 2. 相似文献
18.
Barley ( Hordeum vulgare) protoplasts were incubated in darkness and in the light at saturating and limiting CO 2 concentrations. The protoplasts were fractioned by a membrane filtration technique which allows quenching of the metabolism by acidification within about 0.1 s and the ATP/ADP ratios in the cytasol, chloroplasts and mitochondria were determined. It is concluded that the cytosolic ATP/ADP ratio is considerably higher during photosynthesis at limiting CO 2 (which is the normal situation for a C 3 plant in air) compared to photosynthesis at saturating CO 2 or darkness. 相似文献
19.
Using manometric and enzymic techniques, H 2 and CO 2 evolution in darkness and light has been studied in the green alga Chlamydomonas reinhardtii F-60. F-60 is a mutant strain characterized by an incomplete photosynthetic carbon reduction cycle but an intact electron transport chain. 相似文献
20.
为了进一步了解光照下植物呼吸作用的内在机理以及呼吸作用和光合作用的关系,该文研究了在光照下菜豆(Phaseolus vulgaris)叶片抗氰呼吸与光合作用的关系。研究发现,将黑暗下生长的菜豆幼苗叶片转到光照下10 h,总呼吸、抗氰呼吸以及抗氰呼吸在总呼吸中的比例均逐步上升;光照也导致了叶片叶绿体光合放氧和CO2固定的出现及其速率的增加,但光合放氧和CO2固定速率的增加均滞后于抗氰呼吸的增加。将黑暗下生长的叶片转到光照下之前用抗氰呼吸的抑制剂水杨基氧肟酸(SHAM)处理叶片,发现用SHAM处理并没有导致叶片在光照下光合放氧和CO2固定速率的明显变化,这也提示了黑暗下生长的叶片转至光照的过程中,抗氰呼吸和光合作用没有产生偶联。进一步研究发现,在黑暗中对叶片施加短时间的光照能够增加抗氰呼吸在总呼吸中的比例,但短时间的光照对叶片光合CO2固定速率没有影响。这些结果表明了光照对抗氰呼吸的诱导可以不依赖于光合作用,光照可能是作为一种直接的信号去诱导抗氰呼吸。 相似文献
|