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1.
Cyanophage LPP1G is reproduced at the same yield in heterotrophic conditions (dark, glucose) as in photoautotrophic conditions; aerobiosis is required for dark cyanophage replication. Exogenous glucose is not required for the cyanophage replication in the dark in heterotrophically grown cells. In photoautotrophically grown cells, the maximum burst size in dark and glucose is delayed for a period corresponding to glucose uptake induction. Cyanophage LPP2SPI replication occurs in conditions where only Photosystem I operates. Of photosynthesis parameters tested, only CO 2 photoassimilation is affected during cyanophage LPP1G infection under photoautotrophic conditions. 相似文献
2.
Potential competition between CO 2 and NO 2− photoassimilation for photogenerated reductant ( e.g. reduced ferredoxin and NADPH) was examined employing isolates of mesophyll cells and intact chloroplasts derived from mature `source' spinach leaves. Variations in the magnitude of incident light energy were used to manipulate the supply of reductant in situ within chloroplasts. Leaf cell and plastid isolates were fed with saturating CO 2 and/or NO 2− to produce the highest demand for reductant by CO 2 and/or NO 2− assimilatory processes (enzymes). Even in the presence of CO 2 fixation, NO 2− reduction in intact leaf cell isolates as well as plastid isolates was maximal at light energies as low as 50 to 200 microeinsteins per second per square meter. Simultaneously, 500 to 800 microeinsteins per second per square meter were required to support maximal CO 2 assimilation. Regardless of the magnitude of the incident light energy, CO 2 assimilation did not repress NO 2− reduction, nor were these two processes mutually repressed. These observations have been interpreted to mean that reduced ferredoxin levels in situ in the plastids of mature source leaf mesophyll cells were adequate to supply the concurrent maximal demands exerted by enzymes associated with CO 2 as well as with inorganic nitrogen photoassimilation. 相似文献
3.
The effects of photosynthetic inhibitors and light-dark regimes on the replication of cyanophage SM-2 in its host cyanobacteria ( Synechococcus elongatus UTEX 563 and Microcystis aeruginosa NRC-1, Synechococcus NRC-1 UTEX 1937) have been investigated. Photoassimilation of CO 2 by infected cells was enhanced and remained elevated until late in the infection cycle. Photosynthetic inhibitors and the removal of light suppressed viral replication. SM-2, like other cyanophage of unicellular cyanobacteria, is highly dependent on host photosynthetic metabolism for the energy required in replication.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- CCCP
carbonyl-cyanide m-chlorophenyl hydrazone
- MMH
Modified Modified Hughes Medium 相似文献
4.
1. The effect of H 2 tension, CO 2 tension, pH, time, light intensity, density of suspension, salt content of the medium, and certain spectral regions on the rate of photoassimilation of H 2 and CO 2 by Streptococcus varians has been studied. 2. The method of making light absorption measurements with thin suspensions of bacteria is described. 3. A light source, optical system, and filter for isolating 852 mµ with 894 mµ in sufficient intensity for photochemical work and an improved design of thermostat are given. 4. The photoassimilation of 2H 2 with 1CO 2 apparently involves little over all energy change but nevertheless requires 4 quanta. 相似文献
5.
The photoassimilation of 14CO 2 by washed cells of the photosynthetic bacterium Rhodopseudomonas capsulata was greatly inhibited in air. The inhibition was partially reversed by either sparging with argon or by adding inhibitors, e.g. CO [50% (v/v) in air] and NaN 3 (0.2 mM), which at these concentrations effectively restricted respiration. The effect of oxygen on the photoassimilation of 14CO 2 may be associated with a change in the redox state of the cells resulting in less reducing equivalents being available for this process. 相似文献
6.
Blue light was shown to regulate the utilization of oxidized nitrogen sources by green algae, both by activating nitrate reductase and promoting nitrite reductase biosysnthesis (MA Quiñones, PJ Aparicio [1990] Inorganic Nitrogen in Plants and Microorganisms, Springer-Verlag, Berlin, pp 171-177; MA Quiñones, PJ Aparicio [1990] Photochem Photobiol 51: 681-692). The data reported herein show that, when cells of Monoraphidium braunii at pH 8, containing both active nitrate reductase and nitrite reductase, were sparged with CO 2-free air and irradiated with strong background red light, they took up oxidized nitrogen sources only when PAR comprised blue light. The activation of the transport system(s) of either both nitrate and nitrite was very quick and elicited by low irradiance blue light. In fact, blue light appears to act as a switch signal from the environment, since the uptake of these anions immediately ceased when this radiation was turned off. The requirement of blue light for nitrate uptake was independent of the availability of CO 2 to cells. However, cells under high CO 2 tensions, although they showed an absolute blue light requirement to initially establish the uptake of nitrite, as they gained carbon skeletons to allocate ammonia, gradually increased their nitrite uptake rates in the subsequent red light intervals. Under CO 2-free atmosphere, cells irradiated with strong background red light of 660 nanometers only evolved oxygen when they were additionally irradiated with low irradiance blue light and either nitrate or nitrite was present in the media to provide electron acceptors for the photosynthetic reaction. 相似文献
7.
A careful restudy of the photosynthetic process of barley ( Hordeum vulgare) infected with powdery mildew ( Erysiphe graminis f. sp. hordei) is reported. Unlike previous reports, which indicated a stimulation in infected host tissue photosynthesis during early stages of the disease followed by a rapid decline in activity, this study observed no stimulation but instead a biphasic inhibition in infected host photosynthesis under physiological concentrations of CO 2. Under high CO 2 (1.0%) a stimulation was observed during early stages of infection. The inhibition in low CO 2 and stimulation in high CO 2 of infected host photosynthesis was shown to occur in healthy host tissue when in the presence of 10 −2m α-hydroxy-2-pyridinemethanesulfonic acid. The possible significance of these similar results is discussed. 相似文献
8.
Cells of Anabaena PCC 7119 and of a mutant strain of Nostoc muscorum unable to fix dinitrogen, grown at pH 8 and under low CO 2 tension (air), showed a reduced capacity for photosynthesis when cultured in the absence of sodium, this inhibition being followed by symptoms of photooxidation, such as chlorosis, oxygen consumption in the light, and decrease of superoxide dismutase activity. The impairment of photosynthesis preceded that of nitrogenase activity, indicating that the requirement for sodium in photosynthesis was independent of its effects on nitrogen metabolism. However, when cyanobacteria were grown at pH 6.3 or under high CO 2 tensions, sodium was not required for photosynthesis and no symptoms of photooxidation were observed. 相似文献
9.
Glycidate (2,3-epoxypropionate) increased CO 2 photoassimilation in intact spinach ( Spinacia oleracea L.) chloroplasts in the presence of various inhibitors of photosynthesis, including O 2, arsenite, azide, iodo-acetamide, and carbonylcyanide 3-chlorophenylhydrazone. Although the mechanism by which glycidate enhances photosynthesis is obscure, the stimulatory effect cannot be ascribed to either an inhibition of glycolate formation, a specific interaction with the O 2 inhibition of photosynthesis, or a direct effect on the ribulose 1,5-bisphosphate carboxylase (EC 4.1.1.39) reaction. The lack of a differential effect of glycidate on photosynthesis and glycolate formation in the isolated chloroplast was confirmed in whole leaf studies by the CO 2 compensation concentration assay. These results are at variance with the report that glycidate stimulates net photosynthesis in tobacco leaf disks by irreversibly inhibiting glycolate formation and thus photorespiration (Zelitch, I., 1974, Arch. Biochem. Biophys. 163: 367-377). 相似文献
10.
The influence of pH upon the O 2 inhibition of 14CO 2 photoassimilation (Warburg effect) was examined in intact spinach ( Spinacia oleracea) chloroplasts. With conditions which favored the Warburg effect, i.e. rate-limiting CO 2 and 100% O 2, O 2 inhibition was greater at pH 8.4 to 8.5 than at pH 7.5 to 7.8. At pH 8.5, as compared with 7.8, there was an enhanced 14C-labeling of glycolate, and a decrease of isotope in some phosphorylated Calvin cycle intermediates, particularly triose-phosphate. The 14C-labeling of starch was also more inhibited by O 2 at higher pH. The enhanced synthesis of glycolate during 14CO 2 assimilation at higher pH resulted in a diminution in the level of phosphorylated intermediates of the Calvin cycle, and this was apparently a causal factor of the increased severity of the Warburg effect. 相似文献
11.
Previously, C Baysdorfer and JM Robinson (1985 Plant Physiol 77: 318-320) demonstrated that, in a reconstituted spinach chloroplast system, NADP photoreduction functioning at most maximal rate and reductant demand, was the successful competitor with NO 2− photoreduction for reduced ferredoxin. This resulted in a repression of NO 2− reduction until all NADP available had been almost totally reduced. Further experiments, employing isolated, intact spinach leaf plastids and soybean leaf mesophyll cells, were conducted to examine competition for reductant between CO 2 and NO 2− photoassimilation, in situ. In isolated, intact plastid preparations, regardless of whether the demand for reductant by CO 2 photoassimilation was high (5 millimolar `CO 2') with rates of CO 2 fixation in the range 40 to 90 micromoles CO 2 fixed per hour per milligram chlorophyll, low (0.5 millimolar `CO 2') with rates in the range 5 to 8 micromoles CO 2 per hour per milligram chlorophyll, or zero (no `CO 2'), NO 2− photoreduction displayed equal rates in the range of 8 to 22 micromoles per hour per milligram chlorophyll. In the absence of `CO 2', but in the presence of saturating white light, 3-phosphoglycerate photoreduction at rates of 82 to 127 micromoles per hour per milligram chlorophyll did not repress, and occasionally stimulated concomitant rates of NO 2− reduction which ranged from 23.4 to 38.5. Conversely, in plastid preparations, NO 2− at levels of 50 to 100 micromolar, stimulated plastid CO 2 fixation when `CO 2' was saturating with respect to carboxylation. Further, levels of NO 2− in the range 250 to 2500 micromolar, stimulated soybean leaf mesophyll cell net CO 2 fixation as much as 1.5-fold if `CO 2' was saturating with respect to CO 2 fixation. It appeared likely that, in high light in vivo, CO 2 and NO 2− photoassimilatory processes are not forced to intercompete for reduced ferredoxin in the intact chloroplast. 相似文献
12.
Nitrogen-limited and nitrogen-sufficient cell cultures of Selenastrum minutum (Naeg.) Collins (Chlorophyta) were used to investigate the dependence of NH 4+ assimilation on exogenous CO 2. N-sufficient cells were only able to assimilate NH 4+ maximally in the presence of CO 2 and light. Inhibition of photosynthesis with 3-(3,4-dichlorophenyl)-1,1-dimethylurea, diuron also inhibited NH 4+ assimilation. These results indicate that NH 4+ assimilation by N-sufficient cells exhibited a strict requirement for photosynthetic CO 2 fixation. N-limited cells assimilated NH 4+ both in the dark and in the light in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, diuron, indicating that photosynthetic CO 2 fixation was not required for NH 4+ assimilation. Using CO 2 removal techniques reported previously in the literature, we were unable to demonstrate CO 2-dependent NH 4+ assimilation in N-limited cells. However, employing more stringent CO 2 removal techniques we were able to show a CO 2 dependence of NH 4+ assimilation in both the light and dark, which was independent of photosynthesis. The results indicate two independent CO 2 requirements for NH 4+ assimilation. The first is as a substrate for photosynthetic CO 2 fixation, whereas the second is a nonphoto-synthetic requirement, presumably as a substrate for the anaplerotic reaction catalyzed by phospho enolpyruvate carboxylase. 相似文献
13.
Light-activated hydrogen and oxygen evolution as a function of CO 2 concentration in helium were measured for the unicellular green alga Chlamydomonas reinhardtii. The concentrations were 58, 30, 0.8 and 0 ppm CO 2. The objective of these experiments was to study the differential affinity of CO 2/HCO
3
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for their respective Photosystem II and Calvin cycle binding sites vis-à-vis photoevolution of molecular oxygen and the competitive pathways of hydrogen photoevolution and CO 2 photoassimilation. The maximum rate of hydrogen evolution occurred at 0.8 ppm CO 2, whereas the maximum rate of oxygen evolution occurred at 58 ppm CO 2. The key result of this work is that the rate of photosynthetic hydrogen evolution can be increased by, at least partially, satisfying the Photosystem II CO 2/HCO
3
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binding site requirement without fully activating the Calvin-Benson CO 2 reduction pathway. Data are presented which plot the rates of hydrogen and oxygen evolution as functions of atmospheric CO 2 concentration in helium and light intensity. The stoichiometric ratio of hydrogen to oxygen changed from 0.1 at 58 ppm to approximately 2.5 at 0.8 ppm. A discussion of partitioning of photosynthetic reductant between the hydrogen/hydrogenase and Calvin-Benson cycle pathways is presented.Abbreviations PET
photosynthetic electron transport
- PS
Photosystem 相似文献
14.
Biomass production by the green algae Scenedesmus obliquus and Chlorella vulgaris in intensive laboratory continuous cultures was considerably affected by the pH at which the cultures were maintained. Carbon photoassimilation experiments revealed that pH values in the range of 8 to 9 were important for determining the free CO 2 concentrations in the medium. With higher pH values, additional pH effects were observed involving a decrease in the relative high affinity of low CO 2-adapted algae to free CO 2. The carbon uptake rate by high CO 2-adapted algae after transfer to low free CO 2 medium was characterized by a lag period of about 30 min, after which the affinity of the algae to CO 2 increased considerably. Both continuous growth and carbon uptake experiments indicated that artificially maintained high free CO 2 concentrations are recommended for maximal production in intensive outdoor algal cultures. 相似文献
15.
The pod wall of pea ( Pisum sativum L.) was shown to contain two distinct photosynthetic layers. The outer, comprising chlorenchyma of the mesocarp, captured CO 2 from the outside atmosphere; the inner, a chloroplast-containing epidermis lining the pod gas cavity, was involved in photoassimilation of the CO 2 released from respiring seeds. 相似文献
16.
The effect of light intensity on the rates of ammonium and nitrate uptake and of CO 2 fixation has been determined in intact Anacystis nidulans cells. Ammonium uptake became saturated at photon flux values of about 60 microeinsteins per square meter per second, whereas both nitrate uptake and CO 2 fixation reached saturation at about 250 microeinsteins per square meter per second, the rates of the two latter processes being tightly correlated at any light intensity assayed. Inhibition of ammonium assimilation resulted in the loss of correlation between CO 2 fixation and nitrate uptake, the latter process exhibiting then a reduced light requirement. The results establish a clear distinction between ammonium utilization and nitrate utilization with regard to their light requirement and to the nature of their dependence upon CO 2 fixation. 相似文献
17.
The current study evaluated photosynthetic processes in two clover species based on their performance under high O 3 conditions (150 nl l –1 for 3 h). These species are Trifolium repens L. and Trifolium pratense L., which are well known for their different sensitivity to ozone. Ozone affected the two clover species very differently. In T. pratense, ozone induced visible symptoms of damage even though CO 2 photoassimilation, stomatal conductance and the electron transport rate were not affected. A decrease in the optimal quantum yield was observed in T. pratense immediately after the end of the period of O 3 stress but it reverted to a value similar to the control 24 h after removing the stress, indicating that non-irreversible photoinhibition had occurred. Data obtained for symptomatic T. pratense indicate that still-green living tissue of the leaf is able to carry out CO 2 assimilation; the only parameter found to be affected by O 3 was the efficiency of excitation capture. In T. repens, acute O 3 fumigation induced inhibition of photosynthetic activity, enhanced stomatal closure and increased the reduction state of the PSII primary acceptor. A possible explanation for the inhibition of photosynthesis could reside in inhibition of the Calvin cycle over-reducing PSII, thus increasing (1 – qP) and increasing non-photochemical quenching. 相似文献
18.
- Accumulation of glycogen up to a constant amount per cell was observed during the post-exponential phase of growth, in the presence of an excess of a utilizable carbon source. Cell multiplication was reproducibly controlled by growth of the organism in a nitrogen-limiting medium under photoautotrophic conditions (presence of light, air plus CO2).
- Temporary starvation, i.e. by removal of light or by the addition to an illuminated culture of DCMU, 3-(3′,4′-dichlorophenyl)-1,1′-dimethylurea, a specific inhibitor of photosystem II, lead to a mobilization of glycogen in the cell. Furthermore, Anacystis nidulans, having accumulated glycogen by virtue of preculture under nitrogen-limiting conditions, will resume cell division when the culture medium is complemented with a nitrogen source. The ability of the organism to use glycogen as an endogenous carbon source for growth was observed by addition of a nitrogen source to nitrogen-starving cells and simultaneous removal of CO2.
- During the period of constant amount of glycogen per cell the reserve polysaccharide was subject to turnover as demonstrated with a pulse chase-labelling technique. The demonstration of a turnover—for the first time with a bacterial species—indicated a strict balance in the relative rate of synthesis and degradation.
相似文献
19.
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
20.
Photoassimilation of 14CO 2 by intact chloroplasts from the Crassulacean acid metabolism plant Sedum praealtum was investigated. The main water-soluble, photosynthetic products were dihydroxyacetone phosphate (DHAP), glycerate 3-phosphate (PGA), and a neutral saccharide fraction. Only a minor amount of glycolate was produced. A portion of neutral saccharide synthesis was shown to result from extrachloroplastic contamination, and the nature of this contamination was investigated with light and electron microscopy. The amount of photoassimilated carbon partitioned into starch increased at both very low and high concentrations of orthophosphate. High concentrations of exogenous PGA also stimulated starch synthesis. DHAP and PGA were the preferred forms of carbon exported to the medium, although indirect evidence suported hexose monophosphate export. The export of PGA and DHAP to the medium was stimulated by high exogenous orthophosphate, but depletion of chloroplastic reductive pentose phosphate intermediates did not occur. As a result only a relatively small inhibition in the rate of CO2 assimilation occurred. The rate of photoassimilation was stimulated by exogenous PGA, ribose 5-phosphate, fructose 1,6-bisphosphate, fructose 6-phosphate, and glucose 6-phosphate. Inhibition occurred with phosphoenolpyruvate and high concentrations of PGA and ribose 5-phosphate. PGA inhibition did not result from depletion of chloroplastic orthophosphate or from inhibition of ribulose 1,5-bisphosphate carboxylase. Exogenous PGA and phosphoenolpyruvate were shown to interact with the orthophosphate translocator. 相似文献
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