No abstract

Two trees of radiata pine, one showing severe lean, the other growing almost vertically, were assessed for the presence and anatomical properties of compression wood, including anatomy, lignin distribution, microfibril angle, basic density, radial and tangential lumen diameter and cell wall thickness. Both trees contained significant amounts of compression wood although the severity and amount of compression wood was greater in the leaning tree. Changes in lignin distribution seem to be characteristic of the mildest forms of compression wood with reduced lignification of the middle lamella representing the earliest change observed from normal wood. An increase in microfibril angle was associated with both mild and severe compression wood although examples of severe compression wood with the same or smaller microfibril angles than opposite wood, or with very small microfibril angles, were found. When segregated into mild and severe compression wood the average difference in microfibril angle was 4° and 8° respectively compared with opposite wood. Within-ring distribution of microfibril angle was different in severe compression wood compared to opposite wood with higher angles in the latewood.Severe compression wood showed a 22% increase in basic density compared to mild compression wood and opposite wood. The increased density was accounted for in terms of a 26% increase in tracheid wall thickness throughout the growth ring, offset by a 9% increase in radial lumen diameter, slightly greater in the latewood. There were no significant changes in density or cell dimensions in mild compression wood compared with opposite wood.

Production and replacement of fine roots (diam. < 1 mm) takes 8–67% of net primary production in forests. Most of this production is lost through mortality; little appears as an increment. Traditional biomass methods underestimate fine-root production because estimating production or mortality from changes in standing crop alone does not adequately account for simultaneous and compensating processes of growth, death, and replacement which occur continuously. We propose a compartment–flow model to solve this problem and estimate fine-root production and mortality at a monthly resolution for a pine plantation in New Zealand. The main component of the model is fine-root decomposition, an exponential decay function driven by soil temperature. The model "produces" and "turns over" enough fine roots to maintain observed standing crops of live and dead fine roots given losses through decomposition each month. We have formulated the model as differential and difference equations. Monthly estimates from the model indicated smooth modal patterns. Production and mortality peaked in early spring (September) at about 600 kg•ha−1•month−1 and fell to near zero in summer (January–February). The periodicity of these two processes was out of phase with soil temperature at 10 cm. Decomposition occurred continuously; it peaked in early summer (December) and declined to low levels during winter and was in phase with soil temperature. In a validation of the decomposition portion of the model with an independent set of decomposition data, measured standing crops of dead fine root were not statistically different from predicted values.

Background: The herpes simplex virus type 1 (HSV-1) ICP0 protein is an E3 ubiquitin ligase, which is encoded within the HSV-1 latency-associated locus. When ICP0 is not synthesized, the HSV-1 genome is acutely susceptible to cellular repression. Reciprocally, when ICP0 is synthesized, viral replication is efficiently initiated from virions or latent HSV-1 genomes. The current study was initiated to determine if ICP0's putative role as a viral interferon (IFN) antagonist may be relevant to the process by which ICP0 influences the balance between productive replication versus cellular repression of HSV-1.

Abstract. A novel technique to record the variability of stomatal aperture over the leaf surface is described. This combines observations of leaf surfaces using low‐temperature scanning electron microscopy (LTSEM), with digital image analysis to produce the most accurate aperture measurements obtained to date. Leaf samples are rapidly immobilized by cryo‐fixation in liquid nitrogen and stored in a purpose‐built cryo‐storage system. Specimens can be collected in the field, remote from the cryopreparation system, and stored for up to several weeks before being examined on the LTSEM. The advantages of this method are that the time frame of the measurements is accurately known, and is identical for all stomatal apertures in a sample, and the precision of the measurements is not limited by the resolving power of the microscope. Measurements of stomatal aperture were obtained from leaves of field grown Avena fatua using the above procedure. Leaf surface conductance (gsur) was determined by porometry immediately before cryo‐fixation of the same region of the leaf. Measurements of aperture size showed a high degree of variability within each specimen, with coefficients of variation similar to those found in previous studies. Stomatal conductance (gs) was calculated from stomatal dimensions using formulae derived elsewhere. A linear regression between the computed values of gs and porometric estimates of gsur showed good agreement with the regression line passing through the origin with a slope of 1.0 (R2=0.96). Applications of the experimental system are discussed.