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At least 937 records · Page 52Linked to original sources
PubMed2006

Thermal history regulates methylbutenol basal emission rate in Pinus ponderosa.

Methylbutenol (MBO) is a 5-carbon alcohol that is emitted by many pines in western North America, which may have important impacts on the tropospheric chemistry of this region. In this study, we document seasonal changes in basal MBO emission rates and test several models predicting these changes based on thermal history. These models represent extensions of the ISO G93 model that add a correction factor C(basal), allowing MBO basal emission rates to change as a function of thermal history. These models also allow the calculation of a new emission parameter E(standard30), which represents the inherent capacity of a plant to produce MBO, independent of current or past environmental conditions. Most single-component models exhibited large departures in early and late season, and predicted day-to-day changes in basal emission rate with temporal offsets of up to 3 d relative to measured basal emission rates. Adding a second variable describing thermal history at a longer time scale improved early and late season model performance while retaining the day-to-day performance of the parent single-component model. Out of the models tested, the T(amb),T(max7) model exhibited the best combination of day-to-day and seasonal predictions of basal MBO emission rates.

Algorithms↗
PubMed2007

Assessing environmental and physiological controls over water relations in a Scots pine (Pinus sylvestris L.) stand through analyses of stable isotope composition of water and organic matter.

This study investigated the influence of meteorological, pedospheric and physiological factors on the water relations of Scots pine, as characterized by the origin of water taken up, by xylem transport as well as by carbon isotope discrimination (Delta13C) and oxygen isotope enrichment (Delta18O) of newly assimilated organic matter. For more than 1 year, we quantified delta2H and delta18O of potential water sources and xylem water as well as Delta13C and Delta18O in twig and trunk phloem organic matter biweekly, and related these values to continuously measured or modelled meteorological parameters, soil water content, stand transpiration (ST) and canopy stomatal conductance (G(s)). During the growing season, delta18O and delta2H of xylem water were generally in a range comparable to soil water from a depth of 2-20 cm. Long residence time of water in the tracheids uncoupled the isotopic signals of xylem and soil water in winter. Delta18O but not Delta13C in phloem organic matter was directly indicative of recent environmental conditions during the whole year. Delta18O could be described applying a model that included 18O fractionation associated with water exchange between leaf and atmosphere, and with the production of organic matter as well as the influence of transpiration. Phloem Delta13C was assumed to be concertedly influenced by G(s) and photosynthetically active radiation (PAR) (as a proxy for photosynthetic capacity). We conclude that isotope signatures can be used as effective tools (1) to characterize the seasonal dynamics in source and xylem water, and (2) to assess environmental effects on transpiration and G(s) of Scots pine, thus helping to understand and predict potential impacts of climate change on trees and forest ecosystems.

Carbon Isotopes↗
PubMed2006

Ectomycorrhizal ecology under primary succession on coastal sand dunes: interactions involving Pinus contorta, suilloid fungi and deer.

Ectomycorrhizal fungi (EMF) are critical for pine establishment under primary succession. The species of EMF supporting primary successional pine seedlings on coastal sand dunes and mechanisms for their establishment were investigated. Fungi were identified from ectomycorrhizal roots using molecular techniques. Field seedlings were collected from forested and nonforested zones. Laboratory seedlings were grown in soils collected from the same zones, and in sterile soils inoculated with fresh and 1-yr-old dry deer fecal pellets. Suilloid fungi were frequently observed on all seedlings. A diverse group of fungi was available to seedlings in forested zones. A less diverse group of fungi was available to field seedlings in nonforested zones and all laboratory bioassay seedlings. Deer fecal inoculant yielded an average of two EMF per seedling. Both Suillus and Rhizopogon species dominated seedlings inoculated with fresh deer feces, but only Rhizopogon species dominated seedlings inoculated with 1-yr-old feces. Suilloid fungi are dispersed by deer, produce resistant spore banks and are the principle fungi supporting seedlings on the sand dunes.

Animals↗
PubMed1993

Effects of ingestion of pine needles (Pinus ponderosa) by late-pregnant beef cows on potential sensitive Ca2+ channel activity of caruncular arteries.

Cows were fed either a control (n = 6) or pine needle (n = 12) diet beginning on day 249 of pregnancy. On day 3 and day 5 of feeding, control-fed and pine needle-fed cows were slaughtered and placentomes were collected for in vitro perfusion of the caruncular artery. Potential sensitive Ca2+ channel (PSC) activity as well as the responsiveness to phenylephrine (alpha 1-adrenergic agonist) and adrenaline (alpha 1- and alpha 2-adrenergic agonist) were determined. Selected gravid uterine tissues (endometrium and myometrium, as well as caruncular and cotyledonary tissues) and associated arteries (caruncular, intercaruncular and umbilical) were isolated, minced and portions either extracted immediately for measurement of PSC or frozen at -90 degrees C until assayed for peroxidase activity or number of alpha 2-adrenergic receptors and affinities or for both. In vitro perfused placentomes from day 5 pine needle-fed cows had greater (P < 0.05) PSC activity, as measured by the increase in perfusion pressure in response to a depolarizing dose of KCl, than day 3 pine needle-fed or control-fed cows (10.3 +/- 2.5 versus 6.1 +/- 1.2, and 4.3 +/- 0.7 kPa, respectively). Furthermore, day 5 pine needle-fed cows also exhibited greater (P < 0.05) contractile responses to adrenaline than day 3 pine needle-fed or control-fed cows. Contractile responses to phenylephrine were similar (P > 0.1) for all three treatment groups. The observed increase in PSC activity and responsiveness to adrenaline, however, was not reflected by increasing numbers or affinities of PSC or alpha 2-adrenergic receptors on caruncular arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed2006

Association genetics in Pinus taeda L. I. Wood property traits.

Genetic association is a powerful method for dissecting complex adaptive traits due to (i) fine-scale mapping resulting from historical recombination, (ii) wide coverage of phenotypic and genotypic variation within a single experiment, and (iii) the simultaneous discovery of loci and alleles. In this article, genetic association among single nucleotide polymorphisms (58 SNPs) from 20 wood- and drought-related candidate genes and an array of wood property traits with evolutionary and commercial importance, namely, earlywood and latewood specific gravity, percentage of latewood, earlywood microfibril angle, and wood chemistry (lignin and cellulose content), was tested using mixed linear models (MLMs) that account for relatedness among individuals by using a pairwise kinship matrix. Population structure, a common systematic bias in association studies, was assessed using 22 nuclear microsatellites. Different phenotype:genotype associations were found, some of them confirming previous evidence from collocation of QTL and genes in linkage maps (for example, 4cl and percentage of latewood) and two that involve nonsynonymous polymorphisms (cad SNP M28 with earlywood specific gravity and 4cl SNP M7 with percentage of latewood). The strongest genetic association found in this study was between allelic variation in alpha-tubulin, a gene involved in the formation of cortical microtubules, and earlywood microfibril angle. Intragenic LD decays rapidly in conifers; thus SNPs showing genetic association are likely to be located in close proximity to the causative polymorphisms. This first multigene association genetic study in forest trees has shown the feasibility of candidate gene strategies for dissecting complex adaptive traits, provided that genes belonging to key pathways and appropriate statistical tools are used. This approach is of particular utility in species such as conifers, where genomewide strategies are limited by their large genomes.

Chromosome Mapping↗
PubMed2001

Utilization of different carbon sources by bacteria isolated from the roots of pine seedlings (Pinus silvestris L.) inoculated with root-free, rhizosphere and mycorrhizosphere soil.

Studies were carried out on the utilization of different sugars (glucose, fructose, arabinose, xylose, sucrose) and organic acids (acetic, citric, fumaric, propionic, succinic) by fast and slow growing bacteria isolated from the roots of pine seedlings (P. silvestris L.) inoculated with root-free, rhizosphere and mycorrhizosphere soil from nursery and mature pine forest. Sucrose among sugars and propionic acid among organic acids were the less frequently utilized compounds. Sugars were better carbon sources than organic acids. Proportion of isolates utilizing respective sugars or organic acids was, in general, significantly higher among fast growing bacteria as compared with slow growing ones. No significant differences in number of strains assimilating the appropiate sugars depending on their original habitat or kind of soil were observed. Such differences were noted for utilization of some organic acids. 3-factor ANOVA confirmed that the growth speed of bacteria at the moment of their isolation had the strongest effect on utilization of the compounds studied.

Bacteria↗