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1.
Resistance to CO2 Fixation in the Submerged Aquatic Macrophyte Callitriche stagnalis Scop 总被引:1,自引:0,他引:1
The resistance to the photosynthetic carbon fixation in thefreshwater angiospcrm Callitriche stagnalis Scop was investigatedby gas exchange experiments in a closed water-flow system. Anelectrical analogue model was used to analyse uptake of carbonin terms of boundary layer resistance, cytoplasmic resistanceand carboxylation resistance. The most important rate-limitingfactor was the boundary layer resistance which was from 86%to 91 % of the total resistance of 8521221 s cm1.The cytoplasmic and carboxylation resistances during activephotosynthesis were of minor importance being 89 s cm1and 2430 s cm1, respectively. The calculated thicknessof the boundary layer surrounding the foliage of the shootswas 103155 µm or 23 times the total thicknessof the leaves. The physiological and morphological characteristicsof submerged aquatic macrophytes are discussed as adaptationsto the low availability of carbon due to the high boundary layerresistance. Key words: Aquatic macrophytes, Resistance to carbon fixation, Adaptations 相似文献
2.
Induction of HCO(3) Transporting Capability and High Photosynthetic Affinity to Inorganic Carbon by Low Concentration of CO(2) in Anabaena variabilis
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The apparent affinity of photosynthesis for inorganic carbon in Anabaena variabilis strain M-3 increased during the course of adaptation from high to low CO2 concentration (5% and 0.03% v/v CO2 in air, respectively). This was attributed to an increased ability of the cells to accumulate inorganic carbon during the course of adaptation to low CO2 conditions. The release of phycobiliproteins was used to evaluate the sensitivity of the cells to lysozyme treatment followed by osmotic shock. High CO2-grown cells were more sensitive to this treatment than were low CO2 ones. The efflux of inorganic carbon from cells preloaded with radioactive bicarbonate is faster in high than it is in low CO2-adapted cells. It is postulated that the cell wall or membrane components undergo changes during the course of adaptation to low CO2 conditions. This is supported by electron micrographs showing differences in the cell wall appearance between high and low CO2-grown cells. The increasing ability to accumulate HCO3− and the lessened sensitivity to lysozyme during adaptation to low CO2 conditions depends on protein synthesis. The increase in affinity for inorganic carbon during the adaptation to low CO2 conditions is severely inhibited by the presence of spectinomycin. Incubation in the light significantly lessens the time required for the adaptation to low CO2 conditions. 相似文献
3.
该试验以玉米、花生2∶4间作模式为对象,采用开顶式气室法控制环境CO_2浓度,于2018-2019年设环境CO_2浓度(Ca, 390μmol·mol~(-1))和升高CO_2浓度(Ce, 700μmol·mol~(-1)),以及不施磷(P_0)和施磷(180 kg P_2O_5·hm~(-2),P_(180))处理下,分析CO_2浓度升高对间作玉米和间作花生功能叶光合碳同化关键酶活性、净光合速率以及籽粒产量的影响,以明确CO_2浓度升高影响玉米、花生间作体系光合作用的机理,为将来CO_2浓度升高环境下间作高产高效提供理论基础。结果表明:(1) Ce处理提高了间作玉米功能叶的PEPC、PPDK、NADP-MDH、Rubisco、GAPDH和Ru5PK等光合碳同化酶活性,其中PEPC和NADP-MDH在苗后43 d以及PPDK、Rubisco、GAPDH和Ru5PK在苗后59 d增幅均达到显著水平,此时施磷对其有正向调控作用。(2) Ce处理增强了间作花生功能叶的Rubisco、GAPDH、Ru5PK和FBPase等光合碳同化酶活性,在苗后43 d和59 d增幅均达到显著水平,此时施磷进一步显著提高了Rubisco与FBPase活性。(3) Ce处理下间作玉米、间作花生的净光合速率显著提高,间作玉米、间作花生和间作体系的籽粒产量分别显著提高了4.4%~52.0%、10.3%~24.0%和5.7%~47.0%;CO_2浓度升高和施磷对间作玉米、花生功能叶的净光合速率和间作体系产量具有正协同效应。研究表明,CO_2浓度升高可以通过提高间作玉米功能叶片的PEPC、PPDK、Rubisco、GAPDH和Ru5PK及间作花生功能叶片的Rubisco、GAPDH、Ru5PK和FBPase等光合碳同化酶活性,增强其对CO_2羧化固定能力,提高间作玉米、间作花生的光合速率,最终显著增加玉米、花生及间作体系的产量,并且增施磷肥对其具有正调控效应。 相似文献
4.
Uchino Akira; Samejima Muneaki; Ishii Ryuichi; Ueno Osamu 《Plant & cell physiology》1995,36(2):229-238
The photosynthetic characteristics of Eleocharis baldwinii (Torr.)Chapman, an amphibious leafless plant in the Cyperaceae, wereinvestigated in both the terrestrial form and the submergedform of the plant. Anatomical observation of the culm, whichis the photosynthetic organ in this plant, revealed that theterrestrial form has the Kranz type of anatomy, whereas thesubmerged form has an inner structure that is similar to thatof submerged aquatic plants, with a reduction in both the numberand the size of bundle sheath cells and vascular bundles andrelatively well developed mesophyll cells. In 14C-pulse 12C-chaseexperiments with the terrestrial form, 80% of the total fixed14C was incorporated into C4 dicarboxylic acids after a 10-spulse. The radioactivity in the C4 acids decreased rapidly,while that in sucrose increased to 36% during a 120-s chase.In the submerged form, 64% and 30% of the total fixed 14C wasincorporated into C4 acids and phosphate esters, respectively,after a 10-s pulse. The radioactivity of these compounds decreasedrelatively slowly during a 120-s chase. The specific activitieson a chlorophyll basis of C4 photosynthetic enzymes that areinvolved in the NAD-ME subtype were high in the terrestrialform, while they were intermediate between those of C3 and C4plants in the submerged form. The activity of ribulose 1,5-bisphosphatecarboxylase was 1.5 times higher in the submerged form thanin the terrestrial form. By contrast, the activity of carbonicanhydrase exhibited the reverse tendency. Western blot analysisof soluble proteins extracted from the mesophyll cells and thebundle sheath strands of the terrestrial form demonstrated thatribulose 1,5-bisphosphate carboxylase/oxygenase protein waspresent in the mesophyll cells as well as in the bundle sheathcells, with a higher level in the latter, although phosphoenolpyruvatecarboxylase and pyruvate, Pi dikinase proteins were restrictedto the mesophyll cells. In the submerged form, diurnal fluctuationsin levels of malate were observed with significant fixationof CO2 at night. However, the diurnal changes of malate weresmaller than those reported for CAM plants. These data indicatethat the terrestrial form of Eleocharis baldwinii fixes atmosphericCO2 essentially via the C4 pathway, while the submerged formfixes inorganic carbon via a complex metabolic system that resemblesan intermediate between C3 and C4 metabolism in associationwith a CAM-like profile. (Received September 12, 1994; Accepted November 21, 1994) 相似文献
5.
Internal CO(2) Supply during Photosynthesis of Sun and Shade Grown CAM Plants in Relation to Photoinhibition 总被引:1,自引:1,他引:0
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Leaves of Kalanchoë pinnata were exposed in the dark to air (allowing the fixation of CO2 into malic acid) or 2% O2, 0% CO2 (preventing malic acid accumulation). They were then exposed to bright light in the presence or absence of external CO2 and light dependent inhibition of photosynthetic properties assessed by changes in 77 K fluorescence from photosystem II (PSII), light response curves and quantum yields of O2 exchange, rates of electron transport from H2O through QB (secondary electron acceptor from the PSII reaction center) in isolated thylakoids, and numbers of functional PSII centers in intact leaf discs. Sun leaves of K. pinnata experienced greater photoinhibition when exposed to high light in the absence of CO2 if malic acid accumulation had been prevented during the previous dark period. Shade leaves experienced a high degree of photoinhibition when exposed to high light regardless of whether malic acid had been allowed to accumulate in the previous dark period or not. Quantum yields were depressed to a greater degree than was 77 K fluorescence from PSII following photoinhibition. 相似文献
6.
无CO_2空气中,小麦、大豆等C_3植物叶片表现出远高于暗呼吸且长时间持续的光下CO_2释放。低氧条件下,叶片RuBP含量显著增加。无HCO_3~-体系中,大豆叶肉细胞积累的光合产物光下损耗明显大于暗中,且主要表现为不伴随可溶性糖相应积累的淀粉迅速降解,淀粉降解酶活性也显著提高。由此表明C_3植物可通过动员其自身贮藏的光合产物,作为补偿碳源,维持CO_2亏缺条件下Calvin循环的运行。 相似文献
7.
8.
Effects of Prolonged Darkness on the Sensitivity of Leaf Respiration to Carbon Dioxide Concentration in C3and C4Species 总被引:3,自引:1,他引:2
Predicting responses of plant and global carbon balance to theincreasing concentration of carbon dioxide in the atmosphererequires an understanding of the response of plant respirationto carbon dioxide concentration ([CO2]). Direct effects of thecarbon dioxide concentration at which rates of respiration ofplant tissue are measured are quite variable and their effectsremain controversial. One possible source of variation in responsivenessis the energy status of the tissue, which could influence thecontrol coefficients of enzymes, such as cytochrome-c oxidase,whose activity is sensitive to [CO2]. In this study we comparedresponses of respiration rate to [CO2] over the range of 60to 1000 µmol mol-1in fully expanded leaves of four C3andfour C4herbaceous species. Responses were measured near themiddle of the normal 10 h dark period, and also after another24 h of darkness. On average, rates of respiration were reducedabout 70% by the prolonged dark period, and leaf dry mass perunit area decreased about 30%. In all species studied, the relativedecrease in respiration rate with increasing [CO2] was largerafter prolonged darkness. In the C3species, rates measured at1000 µmol mol-1CO2averaged 0.89 of those measured at 60µmol mol-1in the middle of the normal dark period, and0.70-times when measured after prolonged darkness. In the C4species,rates measured at 1000 µmol mol-1CO2averaged 0.79 of thoseat 60 µmol mol-1CO2in the middle of the normal dark period,and 0.51-times when measured after prolonged darkness. In threeof the C3species and one of the C4species, the decrease in theabsolute respiration rate between 60 and 1000 µmol mol-1CO2wasessentially the same in the middle of the normal night periodand after prolonged darkness. In the other species, the decreasein the absolute rate of respiration with increase in [CO2] wassubstantially less after prolonged darkness than in the middleof the normal night period. These results indicated that increasingthe [CO2] at the time of measurement decreased respiration inall species examined, and that this effect was relatively largerin tissues in which the respiration rate was substrate-limited.The larger relative effect of [CO2] on respiration in tissuesafter prolonged darkness is evidence against a controlling roleof cytochrome-c oxidase in the direct effects of [CO2] on respiration.Copyright 2001 Annals of Botany Company Carbon dioxide, respiration, Abutilon theophrasti(L.), Amaranthus retroflexus(L.),Amaranthus hypochondriacus (L.), Datura stramonium(L.), Helianthus annuus(L.), Solanum melongena(L.), Sorghum bicolor(L. Moench), Zea mays 相似文献
9.
Photosynthetic Characteristics of C(3)-C(4) Intermediate Flaveria Species : I. Leaf Anatomy, Photosynthetic Responses to O(2) and CO(2), and Activities of Key Enzymes in the C(3) and C(4) Pathways 总被引:10,自引:9,他引:1
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Four species of the genus Flaveria, namely F. anomala, F. linearis, F. pubescens, and F. ramosissima, were identified as intermediate C3-C4 plants based on leaf anatomy, photosynthetic CO2 compensation point, O2 inhibition of photosynthesis, and activities of C4 enzymes. F. anomala and F. ramosissima exhibit a distinct Kranz-like leaf anatomy, similar to that of the C4 species F. trinervia, while the other C3-C4 intermediate Flaveria species possess a less differentiated Kranz-like leaf anatomy. Photosynthetic CO2 compensation points of these intermediates at 30°C were very low relative to those of C3 plants, ranging from 7 to 14 microliters per liter. In contrast to C3 plants, net photosynthesis by the intermediates was not sensitive to O2 concentrations below 5% and decreased relatively slowly with increasing O2 concentration. Under similar conditions, the percentage inhibition of photosynthesis by 21% O2 varied from 20% to 25% in the intermediates compared with 28% in Lycopersicon esculentum, a typical C3 species. The inhibition of carboxylation efficiency by 21% O2 varied from 17% for F. ramosissima to 46% for F. anomala and were intermediate between the C4 (2% for F. trinervia) and C3 (53% for L. esculentum) values. The intermediate Flaveria species, especially F. ramosissima, have substantial activities of the C4 enzymes, phosphoenolpyruvate carboxylase, pyruvate, orthophosphate dikinase, NADP-malic enzyme, and NADP-malate dehydrogenase, indicating potential for C4 photosynthesis. It appears that these Flaveria species may be true biochemical C3-C4 intermediates. 相似文献
10.
In higher plants, the mitochondrial electron transport chain has non-phosphorylating alternative pathways that include the alternative terminal oxidase (AOX). This alternative pathway has been suggested to act as a sink for dissipating excess reducing power, minimizing oxidative stress and possibly optimizing photosynthesis in response to changing conditions. The expression patterns of the AOX genes have been well characterized under different growth conditions, particularly in response to light and temperature stress. Additionally, it has been suggested that mitochondrial electron transport is important for avoiding chloroplast over-reduction and balancing energy partitioning among photosynthesis, photorespiration and respiration. Nonetheless, the role AOX plays in optimizing photosynthetic carbon metabolism is unclear. Therefore, the response of photosynthesis to the disruption of AOX was investigated in the Arabidopsis thaliana T-DNA mutant aox1a (SALK_084897). Gas exchange analysis revealed a lower net CO(2) assimilation rate (A) at high CO(2) concentrations in the aox1a mutant compared to wild type. This decrease in A was accompanied by a lower maximum electron transport rate and quantum yield of PSII, and higher excitation pressure on PSII and non-photochemical quenching. The aox1a mutant also exhibited a lower estimated rate of ribulose 1,5-bisphosphate regeneration, and the ribulose 1,5-bisphosphate content was lower at high CO(2) concentrations, suggesting an ATP limitation of the Calvin-Benson cycle. Additionally, the activity of the malate-oxaloacetate shuttle was lower in the mutant compared to wild type. These results indicate that AOX is important for optimizing rates of photosynthetic CO(2) assimilation in response to rising CO(2) concentration by balancing the NAD(P)H/ATP ratio and rates of ribulose 1,5-bisphosphate regeneration within the chloroplast. 相似文献
11.
(18)O discrimination in CO(2) stems from the oxygen exchange between (18)O-enriched water and CO(2) in the chloroplast, a process catalyzed by carbonic anhydrase (CA). A proportion of this (18)O-labeled CO(2) escapes back to the atmosphere, resulting in an effective discrimination against C(18)OO during photosynthesis (Delta(18)O). By constraining the delta(18)O of chloroplast water (delta(e)) by analysis of transpired water and the extent of CO(2)-H(2)O isotopic equilibrium (theta(eq)) by measurements of CA activity (theta(eq) = 0.75-1.0 for tobacco, soybean, and oak), we could apply measured Delta(18)O in a leaf cuvette attached to a mass spectrometer to derive the CO(2) concentration at the physical limit of CA activity, i.e. the chloroplast surface (c(cs)). From the CO(2) drawdown sequence between stomatal cavities from gas exchange (c(i)), from Delta(18)O (c(cs)), and at Rubisco sites from Delta(13)C (c(c)), the internal CO(2) conductance (g(i)) was partitioned into cell wall (g(w)) and chloroplast (g(ch)) components. The results indicated that g(ch) is variable (0.42-1.13 mol m(-2) s(-1)) and proportional to CA activity. We suggest that the influence of CA activity on the CO(2) assimilation rate should be important mainly in plants with low internal conductances. 相似文献
12.
Effects of elevated CO2 on the tolerance of photosynthesis to acute heat stress in C3, C4, and CAM species 总被引:3,自引:0,他引:3
Wang D Heckathorn SA Barua D Joshi P Hamilton EW Lacroix JJ 《American journal of botany》2008,95(2):165-176
Determining the effect of elevated CO(2) on the tolerance of photosynthesis to acute heat stress (AHS) is necessary for predicting plant responses to global warming because photosynthesis is heat sensitive and AHS and atmospheric CO(2) will increase in the future. Few studies have examined this effect, and past results were variable, which may be related to methodological variation among studies. In this study, we grew 11 species that included cool and warm season and C(3), C(4), and CAM species at current or elevated (370 or 700 ppm) CO(2) and at species-specific optimal growth temperatures and at 30°C (if optimal ≠ 30°C). We then assessed thermotolerance of net photosynthesis (P(n)), stomatal conductance (g(st)), leaf internal [CO(2)], and photosystem II (PSII) and post-PSII electron transport during AHS. Thermotolerance of P(n) in elevated (vs. ambient) CO(2) increased in C(3), but decreased in C(4) (especially) and CAM (high growth temperature only), species. In contrast, elevated CO(2) decreased electron transport in 10 of 11 species. High CO(2) decreased g(st) in five of nine species, but stomatal limitations to P(n) increased during AHS in only two cool-season C(3) species. Thus, benefits of elevated CO(2) to photosynthesis at normal temperatures may be partly offset by negative effects during AHS, especially for C(4) species, so effects of elevated CO(2) on acute heat tolerance may contribute to future changes in plant productivity, distribution, and diversity. 相似文献
13.
Gas Exchange and C Allocation in Dunaliella salina Cells in Response to the N Source and CO2 Concentration Used for Growth 总被引:1,自引:0,他引:1
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The halotolerant alga Dunaliella salina was cultured on 10 mM NH4+ or NO3- with air CO2 or 5% (v/v) CO2. Cells grown on NH4+ rather than NO3- were up to 17% larger in volume but had similar division rates. The photosynthetic K0.5 of dissolved inorganic C per cell was reduced, but the light- and CO2-saturated photosynthesis, dark respiration, and light-independent fixation rates were increased. The cells exhibited 2- to 5-fold greater activities of ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase and carboxykinase, and carbonic anhydrase and more soluble and ribulose-1,5-bisphosphate carboxylase/oxygenase protein. Chlorophyll and [beta]-carotene also increased by 30 to 70%. However, starch and glycerol decreased, indicating that C was reallocated from carbohydrates into protein and pigments by growth on NH4+. Algae cultured on air-CO2 rather than a high CO2 concentration were 44% smaller with 55 to 67% lower cell division rates and thus appeared C-limited, despite the operation of a CO2-concentrating mechanism. Cells cultured on air-CO2 had less protein and starch and 28% more glycerol, but the pigment content was unchanged. In only one growth regime was the cell glycerol concentration sufficient to maintain osmotic equilibrium with the external medium, indicating that an additional osmoticum was required. It appears that the N source, as well as the growth [CO2], substantially modifies photosynthetic and growth characteristics, light-independent C metabolism, and C-allocation patterns of D. salina cells. 相似文献
14.
《Phytochemistry》1986,25(7):1537-1543
The pyruvate, phosphate dikinase activity (PPD, EC 2.7.9.1) associated with crude extracts of leaf tissue of some C3 and C4 plants was determined by phosphoenolpyruvate plus PPi-dependent phosphorylation of AMP. The PPD activity of all C4 plants examined was > 15 nmol/mg protein/min. Several factors contributed to the underestimation of PPD activity in crude extracts of at least some species. Significant PPD activity (> 0.15 nmol/mg protein/min) was not detected in the majority of C3 species but several C3 species and the two CAM species studied exhibited activity in the range 0.4–4 nmol/mg protein/min while the C3 species Avena sativa showed activity up to 8 nmol/mg protein/min. The oat leaf enzyme was partially purified; it exhibited properties similar to those of partially purified PPD from maize. Leaf extracts of the orchids Cymbidium canaliculatum and C. madidum contained high levels of PPD activity similar to the majority of C4 plants. PPD activity has also been shown in other previously unstudied species. 相似文献
15.
Photosynthesis in Flaveria brownii, a C(4)-Like Species: Leaf Anatomy, Characteristics of CO(2) Exchange, Compartmentation of Photosynthetic Enzymes, and Metabolism of CO(2)
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Light microscopic examination of leaf cross-sections showed that Flaveria brownii A. M. Powell exhibits Kranz anatomy, in which distinct, chloroplast-containing bundle sheath cells are surrounded by two types of mesophyll cells. Smaller mesophyll cells containing many chloroplasts are arranged around the bundle sheath cells. Larger, spongy mesophyll cells, having fewer chloroplasts, are located between the smaller mesophyll cells and the epidermis. F. brownii has very low CO2 compensation points at different O2 levels, which is typical of C4 plants, yet it does show about 4% inhibition of net photosynthesis by 21% O2 at 30°C. Protoplasts of the three photosynthetic leaf cell types were isolated according to relative differences in their buoyant densities. On a chlorophyll basis, the activities of phosphoenolpyruvate carboxylase and pyruvate, Pi dikinase (carboxylation phase of C4 pathway) were highest in the larger mesophyll protoplasts, intermediate in the smaller mesophyll protoplasts, and lowest, but still present, in the bundle sheath protoplasts. In contrast, activities of ribulose 1,5-bisphosphate carboxylase, other C3 cycle enzymes, and NADP-malic enzyme showed a reverse gradation, although there were significant activities of these enzymes in mesophyll cells. As indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the banding pattern of certain polypeptides of the total soluble proteins from the three cell types also supported the distribution pattern obtained by activity assays of these enzymes. Analysis of initial 14C products in whole leaves and extrapolation of pulse-labeling curves to zero time indicated that about 80% of the CO2 is fixed into C4 acids (malate and aspartate), whereas about 20% of the CO2 directly enters the C3 cycle. This is consistent with the high activity of enzymes for CO2 fixation by the C4 pathway and the substantial activity of enzymes of the C3 cycle in the mesophyll cells. Therefore, F. brownii appears to have some capacity for C3 photosynthesis in the mesophyll cells and should be considered a C4-like species. 相似文献
16.
C(3)-C(4) Intermediate Species in Alternanthera (Amaranthaceae) : Leaf Anatomy, CO(2) Compensation Point, Net CO(2) Exchange and Activities of Photosynthetic Enzymes
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Two naturally occurring species of the genus Alternanthera, namely A. ficoides and A. tenella, were identified as C3-C4 intermediates based on leaf anatomy, photosynthetic CO2 compensation point (Γ), O2 response of г, light intensity response of г, and the activities of key enzymes of photosynthesis. A. ficoides and A. tenella exhibited a less distinct Kranz-like leaf anatomy with substantial accumulation of starch both in mesophyll and bundle sheath cells. Photosynthetic CO2 compensation points of these two intermediate species at 29°C were much lower than in C3 plants and ranged from 18 to 22 microliters per liter. Although A. ficoides and A. tenella exhibited similar intermediacy in г, the apparent photorespiratory component of O2 inhibition in A. ficoides is lower than in A. tenella. The г progressively decreases from 35 microliters per liter at lowest light intensity to 18 microliters per liter at highest light intensity in A. tenella. It was, however, constant in A. ficoides at 20 to 25 microliters per liter between light intensities measured. The rates of net photosynthesis at 21% O2 and 29°C by A. ficoides and A. tenella were 25 to 28 milligrams CO2 per square decimeter per hour which are intermediate between values obtained for Tridax procumbens and A. pungens, C3 and C4 species, respectively. The activities of key enzymes of C4 photosynthesis, phosphoenolpyruvate carboxylase, pyruvate Pi dikinase, NAD malic enzyme, NADP malic enzyme and phosphoenolpyruvate carboxykinase in the two intermediates, A. ficoides and A. tenella are very low or insignificant. Results indicated that the relatively low apparent photorespiratory component in these two species is presumably the basis for the C3-C4 intermediate photosynthesis. 相似文献
17.
Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila 总被引:3,自引:2,他引:1
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cDNAs encoding the large subunit and a possibly truncated small subunit of the potato tuber (Solanum tuberosum L.) adenosine 5'-diphosphate-glucose pyrophosphorylase have been expressed in Escherichia coli (A.A. Iglesias, G.F. Barry, C. Meyer, L. Bloksberg, P.A. Nakata, T. Greene, M.J. Laughlin, T.W. Okita, G.M. Kishore, J. Preiss, J Biol Chem [1993] 268: 1081-1086). However, some properties of the transgenic enzyme were different from those reported for the enzyme from potato tuber. In this work, extension of the cDNA was performed to elongate the N terminus of the truncated small subunit by 10 amino acids. This extension is based on the almost complete conservation seen at the N-terminal sequence for the potato tuber and the spinach leaf small subunits. Expressing the extended cDNA in E. coli along with the large subunit cDNA yielded a transgenic heterotetrameric enzyme with similar properties to the purified potato tuber enzyme. It was also found that the extended small subunit expressed by itself exhibited high enzyme activity, with lower affinity for activator 3-phosphoglycerate and higher sensitivity toward inorganic phosphate inhibition. It is proposed that a major function of the large subunit of adenosine 5'-diphosphate-glucose pyrophosphorylases from higher plants is to modulate the regulatory properties of the native heterotetrameric enzyme, and the small subunit's major function is catalysis. 相似文献
18.
Regulation of Electron Transport in Photosystems I and II in C3, C3-C4, and C4 Species of Panicum in Response to Changing Irradiance and O2 Levels
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Peterson RB 《Plant physiology》1994,105(1):349-356
Regulation of the quantum yields of linear electron transport and photosystem II photochemistry ([phi]II) with changing irradiance and gas-phase O2 concentration was studied in leaf tissue from Panicum bisulcatum (C3), Panicum milioides (C3-C4), and Panicum antidotale (C4) at 200 [mu]bars of CO2 and 25[deg]C using infrared gas analysis and chlorophyll fluorescence yield measurements. When the O2 level was increased from 14 to 213 mbars at high irradiance, [phi]II increased by as much as 115% in P. bisulcatum but by no more than 17% in P. antidotale. Under the same conditions [phi]II increased to an intermediate degree in P. milioides. Measurements of accumulation of the photooxidized form of the photosystem I reaction center (P700+) based on the light-dependent in vivo absorbance change at 830 nm indicate that the steady-state concentration of P700+ varied in an antiparallel manner with [phi]II when either the irradiance or O2 concentration was changed. Hence, O2-dependent changes in [phi]II were indicative of variations in linear photosynthetic electron transport. These experiments revealed, however, that a significant capacity was retained for in vivo regulation of the apparent quantum yield of photosystem I ([phi]I) independently of [phi]II+ Coordinate regulation of quantum yields of photosystems I and II (expressed as [phi]I:[phi]II in response to changing irradiance and O2 level differed markedly for the C3 and C4 species, and the response for the C3-C4 species most closely resembled that observed for the C4 species. The fraction of total linear electron transport supporting photorespiration at 213 mbars of O2 was negligible in the C4 species and was 13% lower in the C3-C4 species relative to the C3 species as calculated from fluorescence and gas-exchange determinations. At high photon-flux rates and high O2 concentration, the potential benefit to light use for net CO2 uptake arising from lower photorespiration in P. milioides was offset by a reduced capacity for total CO2- and O2-dependent noncyclic electron transport in this species compared with P. bisulcatum. 相似文献
19.
Regulation of Ribulose-1,5-Bisphosphate Carboxylase Activity in Response to Light Intensity and CO(2) in the C(3) Annuals Chenopodium album L. and Phaseolus vulgaris L 总被引:5,自引:5,他引:0
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The light and CO2 response of (a) photosynthesis, (b) the activation state and total catalytic efficiency (kcat) of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c) the pool sizes of ribulose 1,5-bisphosphate, (RuBP), ATP, and ADP were studied in the C3 annuals Chenopodium album and Phaseolus vulgaris at 25°C. The initial slope of the photosynthetic CO2 response curve was dependent on light intensity at reduced light levels only (less than 450 micromoles per square meter per second in C. album and below 200 micromoles per square meter per second in P. vulgaris). Modeled simulations indicated that the initial slope of the CO2 response of photosynthesis exhibited light dependency when the rate of RuBP regeneration limited photosynthesis, but not when rubisco capacity limited photosynthesis. Measured observations closely matched modeled simulations. The activation state of rubisco was measured at three light intensities in C. album (1750, 550, and 150 micromoles per square meter per second) and at intercellular CO2 partial pressures (C1) between the CO2 compensation point and 500 microbars. Above a C1 of 120 microbars, the activation state of rubisco was light dependent. At light intensities of 550 and 1750 micromoles per square meter per second, it was also dependent on C1, decreasing as the C1 was elevated above 120 microbars at 550 micromoles per square meter per second and above 300 microbars at 1750 micromoles per square meter per second. The pool size of RuBP was independent of C1 only under conditions when the activation state of rubisco was dependent on C1. Otherwise, RuBP pool sizes increased as C1 was reduced. ATP pools in C. album tended to increase as C1 was reduced. In P. vulgaris, decreasing C1 at a subsaturating light intensity of 190 micromoles per square meter per second increased the activation state of rubisco but had little effect on the kcat. These results support modelled simulations of the rubisco response to light and CO2, where rubisco is assumed to be down-regulated when photosynthesis is limited by the rate of RuBP regeneration. 相似文献
20.
A Model Describing the Regulation of Ribulose-1,5-Bisphosphate Carboxylase, Electron Transport, and Triose Phosphate Use in Response to Light Intensity and CO(2) in C(3) Plants 总被引:7,自引:6,他引:1
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Sage RF 《Plant physiology》1990,94(4):1728-1734
A model of the regulation of the activity of ribulose-1,5-bisphosphate carboxylase, electron transport, and the rate of orthophosphate regeneration by starch and sucrose synthesis in response to changes in light intensity and partial pressures of CO2 and O2 is presented. The key assumption behind the model is that nonlimiting processes of photosynthesis are regulated to balance the capacity of limiting processes. Thus, at CO2 partial pressures below ambient, when a limitation on photosynthesis by the capacity of rubisco is postulated, the activities of electron transport and phosphate regeneration are down-regulated in order that the rate of RuBP regeneration matches the rate of RuBP consumption by rubisco. Similarly, at subsaturating light intensity or elevated CO2, when electron transport or Pi regeneration may limit photosynthesis, the activity of rubisco is downregulated to balance the limitation in the rate of RuBP regeneration. Comparisons with published data demonstrate a general consistency between modelled predictions and measured results. 相似文献