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Douglas-fir Needles (douglas-fir + needle)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Energy Dissipation and Photoinhibition in Douglas-Fir Needles with a Fungal-Mediated Reduction in Photosynthetic Rates

JOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2002
Daniel K. Manter
Abstract The dissipation of absorbed light and potential for photooxidative damage was explored in Douglas-fir (Pseudotsuga menziesii ) seedlings with and without Phaeocryptopus gaeumannii infection. The presence of P. gaeumannii significantly reduced net CO2 assimilation rates from ca. 6 ,mol/m2/s to 1.5 ,mol/m2/s, without any significant impact on chloroplast pigments. The partitioning of absorbed light-energy to photochemistry or thermal dissipation was determined from chlorophyll fluorescence measurements. Maximum thermal dissipation for both control and infected needles was ca. 80%, consistent with the similar xanthophyll pool sizes in the two treatments. At high photosynthetic photon flux density (PPFD), when thermal dissipation was maximized, the lower photochemical utilization in infected needles resulted in greater amounts of excess absorbed light (ca. 20 and 10% for the infected and control needles, respectively). A second experiment, monitoring changes in photosystem II (PSII) efficiency (Fv/Fm) in response to a 1 h high light treatment (PPFD=2000 ,mol/m2/s) also suggests that infected needles absorb greater amounts of excess light. In this experiment, declines in Fv/Fm were 1.5 times greater in infected needles, despite the similar xanthophyll pool sizes. Furthermore, increases in minimum fluorescence (178 and 122% of initial values for the infected and control needles, respectively) suggest that the reduction in PSII efficiency is largely attributable to photooxidative damage. Finally, reductions in PSII efficiency under high light conditions provide a plausible explanation for the greater pathogenicity (e.g. premature needle abscission) of P. gaeumannii in sun-exposed foliage. [source]

Endochitinase activity in the apoplastic fluid of Phellinus weirii -infected Douglas-fir and its association with over wintering and antifreeze activity

FOREST PATHOLOGY, Issue 5 2003
A. Zamani
Summary Extracellular proteins were extracted from Phellinus weirii infected Douglas-fir (Pseudotsuga menziesii var. menziesii) roots and needles to examine endochitinase activity. Chitinases have been associated with the plant's defence response against fungal attack because they hydrolyse chitin, a structural component of fungal cell walls. Protein separation using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Western immunoblot analysis using a polyclonal antibody specific to an endochitinase-like protein (ECP) resulted in the detection of up to three polypeptides between 27 and 30 kDa in size. Two-dimensional gel electrophoresis (2-D PAGE) followed by Western immunoblot analysis revealed that the apoplastic fluid contained multiple ECP isoforms with isoelectric points (pIs) ranging from 5.3 to 5.8 and molecular masses of 27,30 kDa. Chitinase activity in needle and root tissues was measured spectrophotometrically using a colorimetric assay. A gel overlay technique using glycol chitin as a substrate for endochitinase was applied to confirm that the ECP antibody detected an enzymatically active protein. The apoplastic fluid collected from P. weirii -infected winter Douglas-fir needles showed anti-freeze activity and seasonal analysis of needle tissue showed some evidence of ECP accumulation in winter months. ECP was distributed systemically throughout the tree. Increased levels of endochitinase activity in the region of P. weirii infection supports a physiological role for ECP in the plant defence response. Résumé Les protéines extra-cellulaires ont été extraites des racines et aiguilles de douglas (Pseudotsuga menziesii var menziesii) infectés par Phellinus weirii (Murr.) Gilbn., pour étudier l'activité endochitinase. Les chitinases ont été associées aux réactions de défense des plantes contre les attaques fongiques parce-qu'elles hydrolysent la chitine, un composant de la paroi des cellules fongiques. La séparation des protéines, réalisée par électrophorèse en gel de polyacrylamide avec sodium dodecyl sulfate (SDS-PAGE), suivie par une analyse par Western immunoblot en utilisant un anticorps polyclonal spécifique d'une protéine de type endochitinase (ECP), a permis la détection de 3 polypeptides de taille comprise entre 27 et 30 kDa. Une électrophorèse sur gel en 2-dimensions (2-D PAGE) suivie par une analyse par Western immunoblot a révélé que le fluide apoplastique contient de multiples isoformes d'ECP avec des pI dans une gamme de 5.3 à 5.8 et des masses moléculaires de 27 à 30 kDa. L'activité chitinase dans les aiguilles et tissus racinaires a été mesurée par spectrophotométrie par une méthode colorimétrique. Une technique d'overlay utilisant de la chitine glycol comme substrat de l'endochitinase a été appliquée pour confirmer que l'anticorps ECP avait détecté une protéine active du point de vue enzymatique. Le fluide apoplastique d'aiguilles récoltées en hiver sur des douglas infectés par P. weirii a montré une activité antigel et l'analyse saisonnière des tissus foliaires a montré une certaine accumulation d'ECP pendant l'hiver. L'ECP est répartie de façon systémique dans l'ensemble de l'arbre. Les niveaux accrus d'activité endochitinase dans la zone infectée par P. weirii suggère un rôle physiologique de l'ECP dans les réactions de défense de la plante. Zusammenfassung Aus Wurzeln und Nadeln von mit Phellinus weirii infizierten Douglasien (Pseudotsuga menziesii var. menziesii) wurden extrazelluläre Proteine extrahiert, um die Endochitinase-Aktivität zu bestimmen. Chitinasen werden mit der pflanzlichen Abwehrreaktion auf Pilzinfektionen in Verbindung gebracht, da sie Chitin, eine Strukturkomponente der pilzlichen Zellwand, hydrolysieren. Die Proteine wurden mit Natrium-Dodecyl-Sulfat-Polyacrylamid-Gelelektrophorese (SDS-PAGE) getrennt, gefolgt von einer Western Immunoblot-Analyse mit einem gegen ein Endochitinase-ähnliches Protein (ECP) spezifischen polyklonalen Antikörper. Hiermit liessen sich bis zu drei Polypeptide zwischen 27-30 kDa nachweisen. Eine zweidimensionale Gelelektrophorese (2-D PAGE) mit anschliessender Western Immunoblot-Analyse ergab, dass die Apoplastenflüssigkeit multiple ECP-Isoformen enthielt (mit pIs von 5,3 bis 5,8 und Molekularmassen von 27 bis 30 kDa). Die Chitinase-Aktivität wurde auch im Nadel- und Wurzelgewebe spektrophotometrisch mit einer Farbreaktion gemessen. Um sicher zu stellen, dass der ECP-Antikörper ein enzymatisch aktives Protein nachwies, wurde eine Gel-Overlay-Methode verwendet, mit Glycolchitin als Substrat für die Endochitinase. Die Apoplastenflüssigkeit der Nadeln von mit P. weirii infizierten Douglasien zeigte in Winterzustand eine Antifrost-Aktivität, ihre Analyse während des gesamten Jahres ergab aber keine Hinweise auf eine ECP-Anreicherung während der Wintermonate. ECP war systemisch im gesamten Baum enthalten. Die erhöhte Endochitinase-Aktivität in Bereichen mit P. weirii -Infektion lässt auf eine physiologische Rolle von ECP in der Pflanzenabwehr schliessen. [source]

Transport and settlement of organic matter in small streams

FRESHWATER BIOLOGY, Issue 2 2010
TRENT M. HOOVER
Summary 1.,After it enters streams, terrestrially derived organic matter (OM) rapidly absorbs water. Using field and laboratory experiments, we examined how this process affected the buoyancy, settling velocity, transport distance and retention locations of four types of organic matter typically found in Pacific coastal streams (,flexible' red alder leaves and three ,stiff' particle types , Douglas-fir needles, red cedar fronds and Douglas-fir branch pieces). 2.,Immersion in water rapidly changed the physical characteristics of alder leaves, Douglas-fir needles and red cedar fronds, which all reached constant still-water settling velocities after only a few days of soaking. In contrast, the settling velocity of branch pieces continued to increase for 13 days, eventually reaching much higher values than any other OM type. Dried alder leaves became negatively buoyant after only two days of immersion, while other types took substantially longer (up to 24 days) before the specific gravity of all particles was >1. 3.,We released saturated OM particles in an experimental channel and found that all particle types travelled further in a fast, shallow ,riffle' than a slow, deep ,pool'. Comparisons with a passive settlement null model indicated that leaves were retained more rapidly than expected in the riffle (by large protruding stones), while the three stiff particle types travelled further than expected (probably due to turbulent suspension) and were retained when they settled in deeper water between larger stones. In pools, passive settlement appeared to dominate the retention of all OM types, with leaves travelling furthest. 4.,These retention patterns corresponded well with those observed when saturated OM particles collected in the field were released in two pools and two riffles in a second-order coastal stream. 5.,When the experimental channel and in-stream data were combined, the retention rates of the three stiff OM types were closely related to calculated Rouse numbers (Rouse number = particle settling velocity/shear velocity), whereas the retention rate of alder leaves was not. This suggests that different physical mechanisms are responsible for the retention of leaves and stiff OM types in shallow streams. [source]

Effects of climate change on labile and structural carbon in Douglas-fir needles as estimated by ,13C and Carea measurements

GLOBAL CHANGE BIOLOGY, Issue 11 2002
ERIC A. HOBBIE
Abstract Models of photosynthesis, respiration, and export predict that foliar labile carbon (C) should increase with elevated CO2 but decrease with elevated temperature. Sugars, starch, and protein can be compared between treatments, but these compounds make up only a fraction of the total labile pool. Moreover, it is difficult to assess the turnover of labile carbon between years for evergreen foliage. Here, we combined changes in foliar Carea (C concentration on an areal basis) as needles aged with changes in foliar isotopic composition (,13C) caused by inputs of 13C-depleted CO2 to estimate labile and structural C in needles of different ages in a four-year, closed-chamber mesocosm experiment in which Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were exposed to elevated temperature (ambient + 3.5 °C) and CO2 (ambient + 179 ppm). Declines in ,13C of needle cohorts as they aged indicated incorporation of newly fixed labile or structural carbon. The ,13C calculations showed that new C was 41 ± 2% and 28 ± 3% of total needle carbon in second- and third-year needles, respectively, with higher proportions of new C in elevated than ambient CO2 chambers (e.g. 42 ± 2% vs. 37 ± 6%, respectively, for second-year needles). Relative to ambient CO2, elevated CO2 increased labile C in both first- and second-year needles. Relative to ambient temperature, elevated temperature diminished labile C in second-year needles but not in first-year needles, perhaps because of differences in sink strength between the two needle age classes. We hypothesize that plant-soil feedbacks on nitrogen supply contributed to higher photosynthetic rates under elevated temperatures that partly compensated for higher turnover rates of labile C. Strong positive correlations between labile C and sugar concentrations suggested that labile C was primarily determined by carbohydrates. Labile C was negatively correlated with concentrations of cellulose and protein. Elevated temperature increased foliar %C, possibly due to a shift of labile constituents from low %C carbohydrates to relatively high %C protein. Decreased sugar concentrations and increased nitrogen concentrations with elevated temperature were consistent with this explanation. Because foliar constituents that vary in isotopic signature also vary in concentrations with leaf age or environmental conditions, inferences of ci/ca values from ,13C of bulk leaf tissue should be done cautiously. Tracing of 13C through foliar carbon pools may provide new insight into foliar C constituents and turnover. [source]