Photosynthetic Oxygen Exchange in Attached Leaves of C4 Monocotyledons

1982 ◽  
Vol 9 (5) ◽  
pp. 553 ◽  
Author(s):  
RT Furbank ◽  
MR Badger
Keyword(s):  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Co2 Concentration ◽  
O2 Evolution ◽  
Co2 Uptake ◽  
O2 Uptake ◽  
Co2 Compensation Point ◽  
Uptake Rates ◽  
Photosynthetic O2 Evolution ◽  
Photosynthetic Oxygen

Photosynthetic O2 evolution, O2 uptake and CO2 uptake by intact leaves from plants of the three C4 decarboxylation types were examined using mass-spectrometric gas-exchange and stable isotope techniques. All species showed a relative insensitivity of O2 uptake to CO2 concentration. The uptake rates observed were between 0.2 and 1 nmol O2 cm-2 S-1 at the CO2 compensation point. At ambient external CO2, NADP-malic enzyme type species showed the lowest average O2 uptake, phosphoenolpyruvate carboxykinase types the highest values, and NAD-malic enzyme types showed intermediate values for O2 uptake. These results are discussed in relation to the contributions to O2 uptake of ribulosebisphosphate oxygenase and photoreduction of oxygen.

Assimilate Source-Sink Relationships in Capsicum annuum L. III. The Effects of Fruit Excision on Photosynthesis and Leaf and Stem Carbohydrates.

1978 ◽  
Vol 5 (1) ◽  
pp. 1 ◽  
Author(s):  
AJ Hall ◽  
FL Milthorpe
Keyword(s):  
Control Mechanism ◽  
Dark Respiration ◽  
Soluble Sugars ◽  
Co2 Concentration ◽  
Co2 Uptake ◽  
Factors Affecting ◽  
Co2 Compensation Point ◽  
Time Period ◽  
Internal Co2 ◽  
Source Sink

Removal of the rapidly growing fruit from a Capsicum plant reduced the rate of net CO2 uptake by its leaves by up to 30% during the time period explored (0.5 - 7 days). This reduction was associated with increases in both the leaf (to about 200%) and intracellular (to about 30%) resistances, these changes having about equal effects on reducing the rate of CO2 uptake. Changes in photorespiration, dark respiration and CO2 compensation point were very small. The rate of CO2 uptake and the associated resistances were also changed by modifying the light regime and other factors affecting the source-sink balance. Changes in the leaf resistance were not attributable to variations in the internal CO2 concentration or in the water economy of the leaf; its control mechanism remains unexplained. The concentration of soluble sugars in the source leaf was completely unaffected but that of polysaccharides was changed by defruiting and by 50% defoliation. However, variations in the intracellular resistance were not closely related to these changes and there is yet no evidence of the nature of its control mechanism. Changes in both soluble sugars and polysaccharides in the stem were more pronounced than in the leaves.

Submergence of Rice. I. Growth and Photosynthetic Response to CO2 Enrichment of Floodwater

1989 ◽  
Vol 16 (3) ◽  
pp. 251 ◽  
Author(s):  
TL Setter ◽  
I Waters ◽  
I Wallace ◽  
P Bhekasut ◽  
H Greenway
Keyword(s):  
Co2 Enrichment ◽  
Co2 Concentration ◽  
O2 Evolution ◽  
Photosynthetic Response ◽  
Submerged Plants ◽  
High Co2 ◽  
Low Co2 ◽  
O2 Concentration ◽  
Photosynthetic O2 Evolution ◽  
Rice Leaves

Growth and photosynthetic response of lowland rice following complete submergence is related to the concentration of CO2 dissolved in floodwater. Submergence of plants in stagnant solution at low CO2 concentration or solution gassed with air at 0.03 kPa CO2 (equilibrium of 0.01 mol m-3 dissolved CO2) decreased carbohydrates, and little or no growth occurred. Plants submerged in solutions gassed with 3-20 kPa CO2 in air (equilibrium of 0.9-6 mol m-3 CO2) showed at most small decreases in carbohydrates, and growth was up to 100% of the non-submerged plants. At pH 7.5, there was little net photosynthetic O2 evolution by detached submerged leaves even at high HCO3- concentrations, which suggests that these rice leaves could utilise only CO2 and not HCO3-. At pH 6.5, O2 evolution in solutions in equilibrium with 7.4 kPa CO2 was 3-4 fold higher than in solutions in equilibrium with 0.6 kPa CO2. Photorespiration was indicated by a decrease in the rate of net O2 evolution with increasing external O2. In stagnant solutions this reduction of O2 evolution was pronounced; at a CO2 concentration of 0.25 mol m-3 net O2 evolution ceased when the O2 concentration in the water had reached only 0.125 mol m-3. The requirement of photosynthesis for a combination of high CO2 concentrations and low external O2 was presumably due to slow diffusion of these gases in the unstirred layer of solution around the leaves.

scholarly journals Site of inhibition by 2-amino-1,1,3-tricyanopropene of photosynthetic oxygen evolution by spinach leaf chloroplasts (Short Communication)

1973 ◽  
Vol 134 (2) ◽  
pp. 663-665
Author(s):  
E. Margaret Burden ◽  
Alan A. Horton
Keyword(s):  
Steady State ◽  
Short Communication ◽  
O2 Evolution ◽  
Photosynthetic Oxygen Evolution ◽  
Photo Oxidation ◽  
Steady State Fluorescence ◽  
Spinach Leaf ◽  
Photosynthetic O2 Evolution ◽  
Photosynthetic Oxygen ◽  
Spinach Leaves

2-Amino-1,1,3-tricyanopropene inhibits photosynthetic O2 evolution, but, unlike 3-(3,4-dichlorophenyl)-1,1-dimethylurea, has little effect on the steady-state fluorescence of chlorophyll. In chloroplasts prepared from spinach leaves and inhibited by 2-amino-1,1,3-tricyanopropene, a 3-(3,4-dichlorophenyl)-1,1-dimethylurea-sensitive photoreduction of ferricyanide may be restored by addition of semicarbazide. It is concluded that 2-amino-1,1,3-tricyanopropene acts at a point close to the photo-oxidation of water.

CO2 Uptake by Barley Leaf Slices as Measured by Photosynthetic O2 Evolution

1976 ◽  
Vol 79 (4) ◽  
pp. 336-346 ◽  
Author(s):  
C.I. Ullrich-Eberius ◽  
U. Lüttge ◽  
L. Neher
Keyword(s):  
O2 Evolution ◽  
Co2 Uptake ◽  
Barley Leaf ◽  
Photosynthetic O2 Evolution

Phosphoenolpyruvate Carboxykinase in C4 Plants: Its Role and Regulation

1997 ◽  
Vol 24 (4) ◽  
pp. 459 ◽  
Author(s):  
Robert P. Walker ◽  
Richard M. Acheson ◽  
László I. Técsi ◽  
Richard C. Leegood
Keyword(s):  
Molecular Mass ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Plants ◽  
Panicum Maximum ◽  
C4 Plant ◽  
Cam Plants ◽  
Crude Extracts ◽  
High Concentrations ◽  
Regulatory Properties

Some of the recent findings which revise our view of the role and regulation of phosphoenolpyruvate carboxykinase (PEPCK) in C4 plants are discussed. Evidence is presented that PEPCK is present at appreciable activities in the bundle-sheath of some NADP-malic enzyme-type C4 plants, such as maize, but it was not detectable in NAD-malic enzyme-type C4 plants. PEPCK is rapidly inactivated in crude extracts of leaves of the C4 plant, Panicum maximum. This inactivation could be prevented by high concentrations of dithiothreitol or by the inclusion of ADP or ATP, suggesting the involvement of thiols at the active site. PEPCK is also subject to rapid proteolysis in crude extracts of a range of C4 plants, resulting in cleavage to a smaller (62 kDa) form. This can be reduced by extraction at high pH and by the inclusion of SDS, but it means that intact PEPCK has never been purified from a C4 plant. The molecular mass of PEPCK varies considerably in C4 plants, unlike C3 and CAM plants in which it is usually 74 kDa. PEPCK is phosphorylated during darkness (and reversed by light) in some C4 plants with PEPCK of a larger molecular mass, such as Panicum maximum (71 kDa), but it was not phosphorylated in the PEPCK-type C4 plant, Sporobolus pyramidalis (69 kDa). The known regulatory properties of PEPCK are discussed in relation to its role in C4 photosynthesis, in particular its sensitivity to regulation by adenylates and by Mn2+.

Gas exchange in nonperfused dog lungs

1981 ◽  
Vol 51 (5) ◽  
pp. 1261-1267 ◽  
Author(s):  
J. W. Shepard ◽  
V. D. Minh ◽  
G. F. Dolan
Keyword(s):  
Gas Exchange ◽  
Minute Ventilation ◽  
Left Lung ◽  
Co2 Concentration ◽  
Gas Transfer ◽  
O2 Uptake ◽  
Tissue Metabolism ◽  
End Tidal

Gas exchange was studied under conditions of zero perfusion both in situ and in vitro. Six dogs, anesthetized with pentobarbital sodium, underwent surgical interruption of both pulmonary and bronchial circulations to the left lung. Despite the absence of perfusion, O2 uptake for the left lung ranged from 0.76 to 0.98 ml/min, whereas CO2 elimination greatly exceeded O2 uptake ranging from 1.68 to 4.34 ml/min. In addition, CO2 output was observed to vary directly with the level of minute ventilation (VE) and inversely with end-tidal CO2 concentration. To investigate the mechanisms responsible for these findings we studied 20 excised, ventilated, but nonperfused dog lungs to evaluate the relative roles of tissue metabolism and transpleural diffusion to gas exchange. The results obtained with these excised lungs under conditions of varying VE and extrapleural gas concentrations indicate that the high respiratory exchange ratios observed in situ can be explained by the greater rate with which CO2 diffuses through the pleura, and that reduced ventilation decreases total gas transfer by decreasing the transpleural partial pressure driving gradient. Our data further document that the concentration of CO2 in alveolar gas may differ significantly from that present in inspired gas under conditions of ventilation-perfusion ratio equal to infinity, and that tissue metabolism as well as transpleural diffusion contribute to gas exchange in nonperfused lung.

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