Efficiency of Tree Crowns and Stemwood Production at Different Canopy Leaf Densities

Variation in the unit leaf rate in trees, i.e. the weight ofwood increment per unit of leaf area, arises from disproportionatechanges in their rates of net photosynthesis and in the allocationof carbohydrates. Changes in unit leaf rate in response to variationsin canopy density were investigated in a thinning experimentestablished in a 36 year-old Douglas fir forest. Tree growthwas estimated from increment cores and leaf area by linear correlationwith sapwood basal area. Net assimilation and mean growth ofindividual trees expressed as basal area and volume decreasedin direct proportion to increase in canopy density from 3.6to 12.0 m²m^–2 of projected leaf area. These relationshipswere linear with multiple correlation coefficients (r²)0.97. Net stand increment, in contrast to unit leaf rate, culminatedas projected leaf area approached 6 m²m^–2 and decreasedat the higher canopy densities due to mortality. The approachdeveloped in this paper could be applicable in predicting growthin response to various silvicultural treatments.     

The serological responses of chickens to mass vaccination with a live V4 Newcastle disease virus vaccine in the field and in the laboratory 2. Layer pullets

Layer chickens on a commercial started pullet farm were vaccinated once at 31 to 52 days of age by drinking water or aerosol with live V4 Newcastle disease virus (NDV) vaccine. Flockmates which had been rehoused in laboratory isolation pens shortly beforehand were similarly vaccinated. Samples of birds were bled at intervals and the serums tested for haemagglutination inhibiting antibody to NDV. Log2 mean titres of up to 4.88 and assumed protection levels (based on the percentage of birds with log2 titres of 4 or greater) of up to 81%, were obtained in the field trials within 4 weeks of vaccination. A subsequent laboratory trial further compared the response of different breeds of chicken to different routes of vaccination. Differences were observed between breeds, routes of vaccination, and parallel field and laboratory trials. The results show that this V4 vaccine can produce an adequate serological response following mass vaccination of Australian layer pullets housed under commercial conditions, and that care should be exercised in extrapolating results obtained under laboratory conditions.     

The Intercarpal Ligaments of the Equine Midcarpal Joint, Part 2: The Role of the Palmar Intercarpal Ligaments in the Restraint of Dorsal Displacement of the Proximal Row of Carpal Bones

Objective— To determine the relative contributions of the palmar intercarpal ligaments in the midcarpal joint to the restraint of dorsal displacement of the proximal row of carpal bones.
Study Design— A biomechanical study of cadaver equine carpi.
Animals or Sample Population— Eight equine forelimbs from six thoroughbred horses.
Methods— With joints in full extension, the radius was dorsally displaced while midcarpal joint displacement was measured. The restraining force at a joint displacement of 1.5 mm was determined from the load-displacement curve. A ligament or pair of ligaments was then cut and the testing procedure repeated. Their contribution to restraining force was calculated as the percentage change in restraining force after the ligament was sectioned. Relative cross-sectional areas of the ligaments tested were measured at the level of the midcarpal joint.
Results— The collateral ligaments were the major contributors to the restraint of dorsal displacement ( P <.001). In all joints, the palmar intercarpal ligaments contributed a greater proportion than the palmar carpal ligament (PCL) ( P <.05). The mean percentage (±SEM) contributions to the restraint of dorsal displacement were 62.8 ± 3.4 for the collateral ligaments, 14.5 ±1.4 for the PCL, and 22.7 ± 2.2 for the palmar intercarpal ligaments. Mean cross-sectional area expressed as a percentage (±SEM) of the total ligamentous area were 9.0 ± 0.3 for the palmar intercarpal ligaments, 27.1 ± 3.0 for the PCL, and 63.8 ± 2.8 for the collateral ligaments.
Conclusions— Despite the small size of the palmar intercarpal ligaments, they play an important role in the restraint of dorsal displacement of the proximal row of carpal bones.
Clinical Relevance— Interpretation, as well as prevention and treatment of intercarpal ligament tearing requires an understanding of their function.     

The effect of methyl bromide fumigation on rhizomania inoculum in the field

The first outbreak of rhizomania disease in the UK occurred in 1987 and was limited to a single sugar-beet crop in Suffolk. In an attempt to prevent the spread of this disease, the crop was first destroyed by herbicide. In 1988, to reduce the level of rhizomania still present in the soil, the field was treated with methyl bromide at a rate of 900 kg/ha prior to seeding for permanent pasture. Levels of methyl bromide were monitored during the fumigation. A mean concentration time product of 5500 mgh/1 was achieved after 72 h at the soil surface and of 3300-4100 mg-h/1 at a soil depth of 0.3 m after 24 h. Soil samples were taken from five plots across the field before and after fumigation. In the plot with the highest initial inoculum levels, further samples were taken at three depths down to 0.61 m. Sugar-beet seedlings were grown in all soil samples as a bait test for rhizomania inoculum. The presence or absence of Polymyxa betae was observed by microscopical examination, and an enzyme-linked immunoassay was used for the detection of beet necrotic yellow vein virus (BNYVV). The results showed that the methyl bromide treatment had reduced rhizomania inoculum and BNYVV in the soil to levels that were undetectable by the procedures used.     

Changes in lipid content, fatty acid composition and lipid class composition of eggs and developing larvae (0–40 days old) of cultured common dentex (Dentex dentex Linnaeus 1758)

Total lipid content, fatty acid (FA) composition and lipid class composition of common dentex eggs spawned at different times and larvae reared under different culture conditions until 40 days posthatch (dph) were analysed to get a general pattern of lipid composition during larval development. Two groups of larvae were kept under starvation to compare their FA composition with that obtained from normally fed larvae. To compare FA use or accumulation during larval development, results were grouped according to the developmental stage of the larvae instead of age in days posthatch. Saturated and monounsaturated FAs decreased along larval development, while polyunsaturated fatty acid (PUFA) content increased. The ratio of docosahexaenoic acid (DHA)/eicosapentaenoic acid shifted from 4 to 5 in early developmental stages to lower than 1 after metamorphosis. Arachidonic acid levels remained constant along larval development. Larvae kept 6 days under starvation consumed most of their n-3 PUFA while conserving the DHA to values at day 0. The results presented here are useful for the design of nutritional experiments, because there were differences detected in terms of lipid and FA composition between developmental stages with higher differences mainly found in first-feeding larvae and early developmental stages.     

Rapid induction of allergic encephalomyelitis in rats without the use of mycobacteria

Rats, in contrast to certain other species of animals reported, have a striking capacity to develop allergic encephalomyelitis within 2 to 3 weeks following one injection of spinal cord antigen combined with Freund's incomplete adjuvant-that is, adjuvant prepared without addition of killed mycobacteria.     

RIBOSOMAL RNA IN THE DEVELOPING CHICK EMBRYO

Developing chick embryos from the stage of primitive-streak formation make ribosomal (28S and 16S) RNA. The size and composition of the RNA appears to be constant throughout the first 7 days of development.