Biomedical subjects

C S Bledsoe

Publications and source records attributed to C S Bledsoe.

6 recordsLinked to original sources

PubMed2005

Application of network theory to potential mycorrhizal networks.

The concept of a common mycorrhizal network implies that the arrangement of plants and mycorrhizal fungi in a community shares properties with other networks. A network is a system of nodes connected by links. Here we apply network theory to mycorrhizas to determine whether the architecture of a potential common mycorrhizal network is random or scale-free. We analyzed mycorrhizal data from an oak woodland from two perspectives: the phytocentric view using trees as nodes and fungi as links and the mycocentric view using fungi as nodes and trees as links. From the phytocentric perspective, the distribution of potential mycorrhizal links, as measured by the number of ectomycorrhizal morphotypes on trees of Quercus garryana, was random with a short tail, implying that all the individuals of this species are more or less equal in linking to fungi in a potential network. From the mycocentric perspective, however, the distribution of plant links to fungi was scale-free, suggesting that certain fungus species may act as hubs with frequent connections to the network. Parallels exist between social networks and mycorrhizas that suggest future lines of study on mycorrhizal networks.

Biodiversity↗

PubMed1986

Effects of pretreatment conditions on ammonium and nitrate uptake by Douglas-fir seedlings.

Effects of pretreatment solutions containing varying concentrations of calcium, potassium, ammonium and nitrate were evaluated by measuring fluxes of the same ions during a subsequent 4-hour uptake by Douglas-fir seedlings. Maximal rate of ammonium uptake (11 microeq g(-1) root dry weight h(-1)) was about 5 times faster than that of nitrate (2 microeq g(-1) root dry weight h(-1)). Ammonium uptake was most rapid after pretreatment with low potassium levels and was unaffected by ammonium pretreatment. Nitrate uptake was most rapid after pretreatment with high levels of nitrate and low levels of potassium. Calcium uptake was greater when nitrate replaced ammonium as the N source. High calcium pretreatment levels depressed subsequent calcium uptake or resulted in calcium release in both ammonium and nitrate experiments. Potassium efflux occurred with both N sources, but the release was less during nitrate uptake than during ammonium uptake. Efflux of potassium is probably associated with the high potassium status of the seedlings and the exchange between potassium and other cations. High levels of potassium in the pretreatment solutions enhanced potassium efflux and caused a reduction in the subsequent rates of uptake of both ammonium and nitrate. Length of pretreatment and seedling size generally did not affect uptake rates.

Journal Article↗

PubMed1984

A comparison of methods for determining compartmental analysis parameters.

The traditional method for determining compartmental analysis parameters relies on a visual selection of data points to be used for regression of data from each cellular compartment. This method is appropriate when the compartments are kinetically discrete and are easily discernible. However, where treatment effects on compartment parameters are being evaluated, a more objective method for determining initial parameters is desirable.Three methods were examined for determining initial isotopic contents and half-times of (86)Rb elution from cellular compartments using theoretical data with known parameters. Experimental data from roots of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) and barley (Hordeum vulgare L.) intact seedlings were also used. The three methods were a visually assisted, linear regression on data of semilog plot of isotope elution versus time, a microcomputer-assisted, linear regression on semilog plot where maximization of the square of the correlation coefficient (r(2)) was the criterion to determine data points needed for each regression and a mainframe computer-assisted, direct nonlinear regression on elution data using a model of the sum of three exponential decay functions. The visual method resulted in the least accurate estimates of compartmental analysis parameters. The microcomputer-assisted and nonlinear regression methods calculated the parameters equally well.

Journal Article↗

PubMed1984

Mycorrhizal effects on potassium fluxes by northwest coniferous seedlings.

In ectomycorrhizae, the relative abilities of mycobiont and host plant to take up and store inorganic nutrients are not easily determined due to the intimate physical relationship of the two components forming the association. Since compartmental analysis of solute elution can estimate cellular compartment pool sizes and unidirectional fluxes across membranes, we have used this method to study ectomycorrhizal coniferous roots. Rubidium-86, used as a tracer for potassium, was loaded into and eluted from intact roots of nonmycorrhizal and mycorrhizal (with the fungus Hebeloma crustuliniformme [Bull.: St. Amans Quél] Douglas fir (Pseudotsuga menziesii [Mirb.] Franco), western hemlock (Tsuga heterophylla [Raf.] Sarg.) and Sitka spruce (Picea sitchensis [Bong.] Carr.) seedlings.Mycorrhizas significantly increased (86)Rb uptake rates while decreasing the amount of (86)Rb released to the external solution. Using compartmental analysis, the flux data suggest that the primary mycorrhizal effects were to increase inward potassium fluxes across the fungal tonoplast and to decrease potassium efflux across the fungal tonoplast, as compared with nonmycorrhizal seedling roots. The result was greater potassium storage, presumably in the fungal vacuole. The three coniferous species responded differently to fungal infection with respect to potassium fluxes. Both cytoplasmic and vacuolar fluxes for mycorrhizal hemlock were 2-fold greater than for spruce and 3-fold greater than for Douglas fir. These results demonstrate the usefulness of compartmental analysis for study of ion fluxes in intact mycorrhizal root systems and suggest that the fungal tonoplast may be the site for regulation of potassium fluxes in these coniferous roots.

Journal Article↗

PubMed1978

Metabolism of Mevalonic Acid in Vegetative and Induced Plants of Xanthium strumarium.

The metabolism of mevalonic acid in Xanthium strumarium L. Chicago plants was studied to determine how mevalonate was metabolized and whether metabolism was related to induction of flowering. Leaves of vegetative, photoperiodically induced, and chemically inhibited cocklebur plants were supplied with [(14)C]mevalonic acid prior to or during a 16-hour inductive dark period. Vegetative, induced, and Tris(2-diethylaminoethyl)phosphate trihydrochloride-treated plants did not differ significantly in the amount of [(14)C]mevalonic acid they absorbed, nor in the distribution of radioactivity among the leaf blade (97%), petiole (2.3%), or shoot tip (0.7%). [(14)C]Mevalonic acid was rapidly metabolized and transported out of the leaves. Possible metabolites of mevalonate were mevalonic acid phosphates and sterols. No detectable (14)C was found in gibberellins, carotenoids, or the phytol alcohol of chlorophyll. Chemically inhibited plants accumulated (14)C compounds not found in vegetative or induced plants. When ethanol extracts of leaves, petioles, and buds were chromatographed, comparisons of chromatographic patterns did not show significant differences between vegetative and induced treatments.

Journal Article↗

PubMed1971

Pyrimidine metabolism in cotyledons of germinating alaska peas.

Cotyledons from Pisum sativum L. cv. Alaska seeds were excised 12, 36, 108, 132, and 156 hours after imbibition in aerated distilled water. They were then incubated under aseptic conditions for 6 hours in solutions containing either uridine-2-(14)C or orotic acid-6-(14)C. Uridine was more extensively degraded to (14)CO(2) at all germination stages than was orotate, and these rates remained essentially constant at each stage. Incorporation of each compound into RNA increased about 2-fold from the 12th to the 156th hour, although the total RNA present decreased slightly over this interval. Paper chromatography of soluble labeled metabolites produced from orotate showed that the capacity to metabolize this pyrimidine increased markedly as germination progressed. Radioactivity in uridine-5'-P, uridine diphosphate-hexoses, and uridine diphosphate increased most, while smaller or less consistent increases in uridine, uracil, uridine triphosphate, and an unidentified UDPX compound were also observed. The data suggest that orotate metabolism was initially limited by orotidine-5'-phosphate pyrophosphorylase or by 5-phosphoribosyl-1-pyrophosphate. Incorporation of uridine into RNA appeared to be limited at the earliest germination periods by conversion of uridine-5'-P to uridine diphosphate. Thus, during the 1st week of germination the orotic acid pathway and a salvage pathway converting uridine into RNA become activated.

Journal Article↗