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Biomedical subjects

M Schaedle

Publications and source records attributed to M Schaedle.

At least 19 recordsLinked to original sources
PubMed1996

Controlling growth and chemical composition of saplings by iteratively matching nutrient supply to demand: a bootstrap fertilization technique.

We developed a fertilization technique that results in the control, and maintenance at defined rates and levels, of growth and tissue composition of plants of different sizes and developmental stages growing at exponential and nonexponential rates in solid media under naturally fluctuating light and temperature regimes. Clonal cottonwood (Populus deltoides Bartr.) saplings were grown in sand. Low concentrations of nutrient solution were added daily at different constant exponentially increasing rates for 20-30 days to produce plants with different growth rates and tissue nutrient composition. Matching nutrient supply to measured growth demand by bootstrapping, where bootstrapping is the use of an iterative equation that calculates demand from either actual or desired growth rates, maintained these differences for 20-40 days. Nutrient additions controlled growth of saplings with growth rates between 2.0 and 4.0% day(-1), heights between 13.9 and 37.5 cm, dry weights between 0.70 and 3.90 g, leaf nitrogen contents between 1.2 and 3.9%, and leaf carbon/nitrogen ratios between 42.1 and 12.5. The technique was reproducible in a greenhouse without temperature, humidity, or light control, and is easily modified to suit different plant species, plants of various sizes, and various growing conditions.

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PubMed1991

Clonal variation of Populus tremuloides responses to diurnal drought stress.

We have developed an automated microprocessor controlled system for subjecting hydroponically grown plants to drought. Pumps and valves were used to move nutrient solutions into and out of a system of culture vessels in a growth chamber to provide periods of drought. Drought conditions were obtained by exposing the roots of hydroponically grown clones of aspen, Populus tremuloides Michx., to air in culture vessels temporarily emptied of nutrient medium. Over a 3-week period, the daily duration of drought was increased from 0 to 6 h. During this period, the plants became increasingly tolerant to drought, as shown by a decreasing propensity to wilt. All three clones sustained diurnal drought periods of 6 h for up to 5 weeks without detectable deterioration of health. Typical drought stress symptoms were observed including inhibition of growth, increased tissue amino acid content, and decreased water, solute, and turgor potentials in young leaves. In all clones, control plants had leaf water potentials between -1.0 and -1.6 MPa, whereas leaf water potentials of drought-treated plants were significantly lower, ranging from -1.7 to -3.0 MPa. Only one of the clones showed a significant decrease in leaf solute potential in response to drought. The decrease in leaf solute potential paralleled the decrease in water potential resulting in no significant difference in turgor potential. The other two clones had nonsignificant decreases to more negative leaf solute potentials under drought conditions resulting in significantly lowered turgor potentials. Leaf water potentials, solute potentials, and turgor potentials of the drought-treated plants returned to control values within two hours after rewatering. The growth inhibitions observed could not have been the consequence of loss of turgor. These results demonstrate genetic differences among aspen clones in water relations responses to drought.

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PubMed1989

Response of tree seedlings to aluminum.

This review focuses on the mechanisms underlying aluminum (Al) toxicity in trees. The major topics discussed include the uptake and localization of Al, effects of Al on growth and composition, factors determining the response to Al, proposed mechanisms of Al resistance, and the occurrence of Al phytotoxicity under field conditions.

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PubMed1988

Sensitivity of red oak (Quercus rubra L.) and American beech (Fagus grandifolia Ehrh.) seedlings to sodium salts in solution culture.

Sodium salt sensitivity of red oak (Quercus rubra L.) and American beech (Fagus grandifolia Ehrh.) was evaluated in solution culture. Both species showed symptoms of salt injury when grown in the presence of less than 10 mM Na. In red oak, leaf symptoms first appeared at a sodium concentration of 6.0 mM and leaf weight was significantly reduced at 7.5 mM Na. Leaf, stem and root dry weights of American beech were significantly reduced in the presence of 4.0 mM sodium. In both species, browning of leaf margins and necrosis were evident in the Na-treated plants. The observed symptoms were associated with high concentrations of sodium in the tissues. Neither species appears to have control over sodium uptake and translocation.

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PubMed1986

Ribulose-1,5-bisphosphate carboxylase activity of Populus tremuloides Michx. bark tissues.

Ribulose-1,5-bisphosphate (RubP) carboxylase was isolated from bark tissue of Populus tremuloides Michx. by a one-step Sephadex G l00-120 column chromatography procedure. The peak fraction had specific activity of 1.3 micromol CO(2) mg(-1) chlorophyll min(-1). The bark RubP carboxylase activity was comparable to that of leaf tissues. Thus, young corticular tissues are photosynthetically competent and contain sufficient RubP carboxylase to account for the reported rates of photosynthesis.

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PubMed1983

System development for linked-fermentation production of solvents from algal biomass.

Five species of the genus Dunaliella (D. tertiolecta, D. primolecta, D. parva, D. bardawil, and D. salina) were examined for glycerol accumulation, growth rate, cell density, and protein and chlorophyll content. The suitability of each algal species for use as a fermentation substrate was judged according to glycerol accumulation and quantities of neutral solvents produced after sequential bacterial fermentations. When grown in 2 M NaCl, with 24 mM NaHCO(3) or 3% CO(2) at 28 degrees C and with 10,000 to 15,000 lx of incident light on two sides of a glass aquarium, four of the five species tested produced ca. 10 to 20 mg of glycerol per liter of culture. Clostridium pasteurianum was found to convert an algal biomass mixture supplemented with 4% glycerol to ca. 16 g of mixed solvents (n-butanol, 1,3-propanediol, and ethanol) per liter. Acetone was not detected. Additionally, it has been demonstrated that Dunaliella concentrates of up to 300-fold can be directly fermented to an identical pattern of mixed solvents. Overall solvent yields were reduced by >50% when fermentations were performed in the presence of 2% NaCl. These results are discussed in terms of practical application in tropical coastal zones.

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PubMed1982

Photosynthesis and Respiration of Developing Populus tremuloides Internodes.

The photosynthetic and respiratory performance of developing internodes of Populus tremuloides was evaluated by infrared gas analysis. Anatomical and morphological transitions were related to metabolic activity. Photosynthetic rates ranged from 6.0 to 10.0 milligrams CO(2) per decimeter squared per hour in the youngest internodes to 2.5 to 3.8 milligrams CO(2) per decimeter squared per hour in internodes with fully developed bark tissues. Respiration exceeded the rate of photosynthesis on the average by a factor of two. Stem photosynthesis increased with temperature up to 40 degrees C and declined steeply between 40 and 50 degrees C. Stem respiration increased nearly linearly to temperatures as high as 50 degrees C.

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PubMed1977

Chloroplast glutathione reductase.

Glutathione reductase (EC 1.6.4.2) activity is present in spinach (Spinacia oleracea L.) chloroplasts. The pH dependence and substrate concentration for half-maximal rate are reported and a possible role in chloroplasts is proposed.

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PubMed1976

Physiological Characteristics of Photosynthesis and Respiration in Stems of Populus tremuloides Michx.

The physiological responses of 6- to 8-year-old aspen (Populus tremuloides Michx.) stems to temperature, light, and CO(2) concentration were investigated in the field throughout the year using infrared CO(2) analysis. Light response studies showed that the rate of gross photosynthesis was linear from 0 to 400 ft-c (0 to 1.6 mw/cm(2) of 400-700 nm) with light saturation being reached between 800 to 1400 ft-c (3.2 to 5.6 mw/cm(2) of 400-700 nm). At this light intensity, the respiratory CO(2) loss was reduced to 10 to 15% of dark rates. Net photosynthetic CO(2) uptake was not observed even at intensities as high as 3400 ft-c (13.6 mw/cm(2) of 400-700 nm). The light response curve was similar for both winter and summer stems.During summer months, the respiratory and photosynthetic rates of the aspen stem increased with temperature at a near constant rate between 5 and 35 C. For winter stems, the gross photosynthetic rate increased in a pattern similar to the dark respiratory rate as the temperature rose from 3 to 17 C. Below 0 C and above 17 C, however, the gross photosynthetic rate fell off in relation to the respiratory rate so that the per cent of CO(2) reassimilated decreased from 75% to less than 50%. Measurable bark photosynthetic activity was not observed below -3 C.The gross photosynthetic rate of stems was not affected when the gas passing through the cuvette contained concentrations of CO(2) ranging from 0 to 580 mul CO(2)/l air.

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PubMed1976

Diurnal and Seasonal Patterns of Photosynthesis and Respiration by Stems of Populus tremuloides Michx.

The photosynthetic and respiratory rates of 5- to 7-year-old aspen stems (Populus tremuloides Michx.) were monitored in the field for 1 year to determine the seasonal patterns. The stem was not capable of net photosynthesis, but the respiratory CO(2) loss from the stem was reduced by 0 to 100% depending on the time of year and the level of illumination as a result of bark photosynthesis. The monthly dark respiratory rate ranged from 0.24 mg CO(2)/dm(2). hr in January to a maximum 7.4 mg CO(2)/dm(2). hr in June. Individual measurements ranged from 0.02 mg CO(2)/dm(2). hr in February to 12.3 mg CO(2)/dm(2). hr in June. Gross photosynthesis followed a pattern similar to the dark respiratory rate. The mean monthly rate was highest in June (1.65 mg CO(2)/dm(2). hr) and lowest in December (0.02 mg CO(2)/dm(2). hr). Individual measurements ranged from 0.0 mg CO(2)/dm(2). hr in winter to 5.5 mg CO(2)/dm(2). hr in July.Winter studies showed that stem respiration continued down to -11 C, the coldest temperature during this study. Upon warning to -3 C, the dark respiratory rate showed a sudden sharp increase (7- to 12-fold) which required many hours to return to normal levels. No measurable photosynthesis occurred below -3 C. Between -3 and 0 C, the maximal photosynthetic rate was reduced to less than 50% of the respiratory rate, but increased to 89% between 5 to 10 C.On a yearly basis, bark photosynthesis in P. tremuloides reduced the stem respiratory CO(2) loss by 28.7% on a daytime basis and an estimated 16 to 18% on a 24-hour basis.

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PubMed1974

A simple carbon dioxide injection system for photosynthetic studies.

A simple carbon dioxide injection system has been developed for the maintenance of CO(2) concentrations in semiclosed cuvette systems suitable for photosynthesis and gaseous pollutant studies. The device injects small volumes of pure carbon dioxide into the cuvette in response to a signal from an infrared gas analyzer.

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PubMed1973

Functional and Structural Changes in Senescing Populus deltoides (Bartr.) Chloroplasts.

Chloroplasts isolated from Populus deltoides leaves were used to study age-dependent changes in the rate of cyclic photophosphorylation. Single leaves were used to measure CO(2) fixation by leaf discs, chlorophyll concentration, and ATP synthesis. The ability of chloroplasts to synthesize ATP diminished steadily from the time of full leaf expansion, regardless whether the results are expressed on a leaf area or chlorophyll basis. This decline in the rates of ATP synthesis was paralleled by the decline in the rate of CO(2) fixation. The results suggest that the efficiency of the membrane-bound ATP synthesizing system declines with age.

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PubMed1972

Photophosphorylation and Carbon Dioxide Fixation by Chloroplasts Isolated from Populus deltoides.

A system has been developed for the isolation of photosynthetically active chloroplasts from leaves of Populus deltoides. A high proportion of the chloroplasts appeared intact. The maximum rates of different photosynthetic processes were as follows: CO(2) fixation 3.5 micromoles per milligram chlorophyll per hour, noncyclic ATP synthesis 10 micromoles per milligram chlorophyll per hour, and cyclic ATP synthesis 300 micromoles per milligram chlorophyll per hour.

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PubMed1967

Ion Absorption and Retention by Chlorella pyrenoidosa. III. Selective Accumulation of Rubidium, Potassium and Sodium.

The selective preference of Chlorella pyrenoidosa for alkali metal cations was found to have the order Rb > K > > > Na. It was demonstrated that a cation of higher preference can replace in the cell cations of lower preference by an ion interchange process.The replacement of Na from the cell by K or Rb occurred against high external Na concentrations up to 450 meq/1 Na.It is suggested that the structural selectivity of the Chlorella cell may be amplified by a chromatographic type repetitive selection process, driven by metabolically dependent unsymmetric shape changes of cellular membranes.

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PubMed1966

Ion Absorption and Retention by Chlorella Pyrenoidosa. II. Permeability of the Cell to Sodium and Rubidium.

The Na and Rb permeability of Chlorella pyrenoidosa were estimated from the rates of radioisotope self-diffusion.The isotopic exchange in absence of net ionic movements followed first order kinetics. This suggested that for sodium, which reached isotopic equilibrium in approximately 90 minutes, the cell behaved as 1 compartment with respect to isotopic exchange. Rubidium in 180 minutes approached isotopic equilibrium by 67%; thus, the existence of a single compartment for Rb has not been demonstrated. Net fluxes, calculated from the isotope exchange data, and expressed on a dry weight and surface area base showed that Na fluxes were approximately 7 times larger than Rb fluxes. Net Na fluxes of 90 milli-equivalents per 100 g dry weight per hour were far in excess of the observed maximum net accumulation of Na. However, Rb fluxes of 13 milliequivalents per 100 g dry weight per hour were of similar magnitude as the rate of Rb accumulation. Thus, permeability could be a limiting factor for Rb but not for Na accumulation. Sodium and Rb fluxes in absence of net ionic movements were inhibited by low temperature, dark air and dark N(2) conditions. This change in flux rates was explained mainly on the basis of metabolically dependent changes in the cell surface layers.Isotope fluxes of Rb were drastically reduced in dark air and dark N(2) in the absence or presence of net cation movements. Dark N(2) essentially eliminated net cation accumulation, whereas dark air had relatively little effect on the net K and Rb accumulation by Chlorella. Thus the 2 major factors involved in net cation accumulation in the Chlorella cell, permeability and processes leading to cation retention, respond differently to metabolic inhibition permitting a separation of these 2 important aspects of cation accumulation.

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