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J A Berry

Publications and source records attributed to J A Berry.

47 records · Page 3Linked to original sources
PubMed1980

Membrane phospholipid phase separations in plants adapted to or acclimated to different thermal regimes.

The phase separation temperatures of total leaf phospholipids from warm and cool climate plants were determined in order to explore the relationship of lipid physical properties to a species' thermal habitat. The separation temperatures were determined by measuring the fluorescence intensity and fluorescence polarization of liposomes labeled with the polyene fatty acid probe trans-parinaric acid. To focus on a single climatic region, Mojave Desert dicots (chiefly ephemeral annuals) were examined, with plants grown under identical conditions whenever possible. Winter active species showed lower phase separation temperatures than the summer active species. A group of warm climate annual grasses showed separation temperatures distinctly higher than those of a group of cool climate grasses, all grown from seed under the same conditions. Growth at low temperature seems correlated with (and may require) a low phase separation temperature. Winter active ephemerals appear genetically programmed to synthesize a mixture of phospholipids which will not phase separate in the usual growth conditions. When the lipids of desert perennials were examined in cool and warm seasons, there was a pronounced seasonal shift in the phase separation temperature, implying environmental influences on lipid physical properties. The relationship of these results to high and low temperature tolerance is discussed.

Journal Article↗
PubMed1980

Oxygen exchange in leaves in the light.

Photosynthetic O(2) production and photorespiratory O(2) uptake were measured using isotopic techniques, in the C(3) species Hirschfeldia incana Lowe., Helianthus annuus L., and Phaseolus vulgaris L. At high CO(2) and normal O(2), O(2) production increased linearly with light intensity. At low O(2) or low CO(2), O(2) production was suppressed, indicating that increased concentrations of both O(2) and CO(2) can stimulate O(2) production. At the CO(2) compensation point, O(2) uptake equaled O(2) production over a wide range of O(2) concentrations. O(2) uptake increased with light intensity and O(2) concentration. At low light intensities, O(2) uptake was suppressed by increased CO(2) concentrations so that O(2) uptake at 1,000 microliters per liter CO(2) was 28 to 35% of the uptake at the CO(2) compensation point. At high light intensities, O(2) uptake was stimulated by low concentrations of CO(2) and suppressed by higher concentrations of CO(2). O(2) uptake at high light intensity and 1000 microliters per liter CO(2) was 75% or more of the rate of O(2) uptake at the compensation point. The response of O(2) uptake to light intensity extrapolated to zero in darkness, suggesting that O(2) uptake via dark respiration may be suppressed in the light. The response of O(2) uptake to O(2) concentration saturated at about 30% O(2) in high light and at a lower O(2) concentration in low light. O(2) uptake was also observed with the C(4) plant Amaranthus edulis; the rate of uptake at the CO(2) compensation point was 20% of that observed at the same light intensity with the C(3) species, and this rate was not influenced by the CO(2) concentration. The results are discussed and interpreted in terms of the ribulose-1,5-bisphosphate oxygenase reaction, the associated metabolism of the photorespiratory pathway, and direct photosynthetic reduction of O(2).

Journal Article↗
PubMed1980

Internal Inorganic Carbon Pool of Chlamydomonas reinhardtii: EVIDENCE FOR A CARBON DIOXIDE-CONCENTRATING MECHANISM.

The external inorganic carbon pool (CO(2) + HCO(3) (-)) was measured in both high and low CO(2)-grown cells of Chlamydomonas reinhardtii, using a silicone oil layer centrifugal filtering technique. The average internal pH values were measured for each cell type using [(14)C]dimethyloxazolidinedione, and the internal inorganic carbon pools were recalculated on a free CO(2) basis. These measurements indicated that low CO(2)-grown cells were able to concentrate CO(2) up to 40-fold in relation to the external medium. Low and high CO(2)-grown cells differed in their photosynthetic affinity for external CO(2). These differences could be most readily explained as being due to the relative CO(2)-concentrating capacity of each cell type. This physiological adaptation appeared to be based on changes in the abilities of the cells actively to accumulate inorganic carbon using an energy-dependent transport system.The energy dependence of CO(2) accumulation was investigated, using the inhibitors methyl viologen, 3-(3,4-dichlorophenyl)-1,1 dimethylurea, carbonyl cyanide trifluoromethoxyphenylhydrazone, and 3,5-di-tert-butyl-4-hydroxybenzylide nemalononitrile. It appears that the concentrating mechanism in both cell types may be dependent upon an energy supply linked to both phosphorylation in general and photophosphorylation. The treatment of low CO(2)-grown cells with the carbonic anhydrase inhibitor ethoxyzolamide decreased the apparent photosynthetic affinity for CO(2). This was correlated with a decrease in the transport of inorganic carbon into the cells.The nature of the CO(2)-concentrating mechanism, particularly with respect to a bicarbonate transport system, is discussed, and its possible occurrence in other algae is assessed.

Journal Article↗
PubMed1978

Effects of low temperature on respiration and uptake of rubidium ions by excised barley and corn roots.

The effect of temperature upon ion uptake and respiration was investigated with excised roots of corn (Zea mays) and barley (Hordeum vulgare). A strong inhibition (Q(10) = 5 to 8) of ion uptake was observed at temperatures below 10 C. At higher temperatures more normal temperature dependencies (Q(10) = 1.3 to 2) were obtained. When the data were plotted according to the Arrhenius relationship, two different activation energies were indicated above and below 10 C. Other studies have related such changes with temperature in activation energy of processes to changes in membrane properties induced by temperature. These results suggest that such phase transitions may affect ion uptake processes. If so, then differences among species in their capacity to maintain normal root function at low soil temperature and to resist low temperature stress may be related to differences in the physical properties of cellular membranes.

Journal Article↗
PubMed1978

Fixation of O(2) during Photorespiration: Kinetic and Steady-State Studies of the Photorespiratory Carbon Oxidation Cycle with Intact Leaves and Isolated Chloroplasts of C(3) Plants.

Mass spectrometric techniques were used to trace the incorporation of [(18)O]oxygen into metabolites of the photorespiratory pathway. Glycolate, glycine, and serine extracted from leaves of the C(3) plants, Spinacia oleracea L., Atriplex hastata, and Helianthus annuus which had been exposed to [(18)O]oxygen at the CO(2) compensation point were heavily labeled with (18)O. In each case one, and only one of the carboxyl oxygens was labeled. The abundance of (18)O in this oxygen of glycolate reached 50 to 70% of that of the oxygen provided after only 5 to 10 seconds exposure to [(18)O]oxygen. Glycine and serine attained the same final enrichment after 40 and 180 seconds, respectively. This confirms that glycine and serine are synthesized from glycolate.The labeling of photorespiratory intermediates in intact leaves reached a mean of 59% of that of the oxygen provided in the feedings. This indicates that at least 59% of the glycolate photorespired is synthesized with the fixation of molecular oxygen. This estimate is certainly conservative owing to the dilution of labeled oxygen at the site of glycolate synthesis by photosynthetic oxygen. We examined the yield of (18)O in glycolate synthesized in vitro by isolated intact spinach chloroplasts in a system which permitted direct sampling of the isotopic composition of the oxygen at the site of synthesis. The isotopic enrichment of glycolate from such experiments was 90 to 95% of that of the oxygen present during the incubation.The carboxyl oxygens of 3-phosphoglycerate also became labeled with (18)O in 20- and 40-minute feedings with [(18)O]oxygen to intact leaves at the CO(2) compensation point. Control experiments indicated that this label was probably due to direct synthesis of 3-phosphoglycerate from glycolate during photorespiration. The mean enrichment of 3-phosphoglycerate was 14 +/- 4% of that of glycine or serine, its precursors of the photorespiratory pathway, in 10 separate feeding experiments. It is argued that this constant dilution of label indicates a constant stoichiometric balance between photorespiratory and photosynthetic sources of 3-phosphoglycerate at the CO(2) compensation point.Oxygen uptake sufficient to account for about half of the rate of (18)O fixation into glycine in the intact leaves was observed with intact spinach chloroplasts. Oxygen uptake and production by intact leaves at the CO(2) compensation point indicate about 1.9 oxygen exchanged per glycolate photorespired. The fixation of molecular oxygen into glycolate plus the peroxisomal oxidation of glycolate to glyoxylate and the mitochondrial conversion of glycine to serine can account for up to 1.75 oxygen taken up per glycolate.These studies provide new evidence which supports the current formulation of the pathway of photorespiration and its relation to photosynthetic metabolism. The experiments described also suggest new approaches using stable isotope techniques to study the rate of photorespiration and the balance between photorespiration and photosynthesis in vivo.

Journal Article↗
PubMed1977

Mechanisms of CO2 fixation in bacterial photosynthesis studied by the carbon isotope fractionation technique.

The carbon isotope discrimination properties of a representative of each of the three types of photosynthetic bacteria Chlorobium thiosulfatophilum, Rhodospirillum rubrum and Chromatium and of the C3-alga Chlamydomonas reinhardii were determined by measuring the ratio of 13CO2 to 12CO2 incorporated during photoautotrophic growth. 2. Chromatium and R. rubrum had isotope selection properties similar to those of C3-plants, whereas Chlorobium was significantly different. 3. The results suggest that Chromatium and R. rubrum assimilate CO2 mainly via ribulose 1,5-diphosphate carboxylase and the associated reactions of the reductive pentose phosphate cycle, whereas Chlorobium utilizes other mechanisms. Such mechanisms would include the ferredoxin-linked carboxylation enzymes and associated reactions of the reductive carboxylic acid cycle.

Carbon Dioxide↗
PubMedDate not supplied

A video-based patient contour acquisition system for the design of radiotherapy compensators.

Recent advances in computer and video technology have enabled significant advances in the field of surface topography measurement. This paper will describe a digital video patient contour acquisition system for the design of radiotherapy beam compensators. The system is mounted on a tray which slides into the collimator of a radiotherapy simulator. The tray holds a source which projects a 1-mm wide fan beam of light along the simulator beam axis onto the patient. The tray also holds a small solid state video camera which views the projected line of light on the patient surface. Video images are digitized and processed on an 80386 based IBM PC-compatible computer. Transverse contours are obtained from one digitized video image or, in case of opposed fields, from two or more image frames taken at different gantry angles. Entire surfaces are measured by scanning the bed longitudinally and acquiring a number of transverse contours. Posterior surfaces are obtained by scanning a mold. A printer produces a template for making the compensator from sheet lead.

Algorithms↗