Seasonal patterns of cytokinins and microclimate and the mediation of gas exchange among canopy layers of mature Acer saccharum trees

Seasonal patterns of cytokinins (CKs) and microclimate were examined in the upper, middle and lower canopy layers of mature Acer saccharum Marsh. (sugar maple) trees to elucidate the potential role of CKs in the mediation of gas exchange. The upper canopy showed a distinctly dissimilar microclimate from the middle and lower canopy layers with higher photosynthetically active radiation and wind speed, but showed no corresponding differences in transpiration (E) or stomatal conductance (g(s)). Although E and g(s) tended to be higher in the upper canopy than in the middle and lower canopies, the differences were not significant, indicating regulation beyond the passive response to changes in microclimate. The upper canopy accumulated significantly higher concentrations of CKs, predominantly as ribosides, and all canopy layers showed distinct seasonal patterns in CK profiles. Multiple regression models showed significant relationships between both g(s) and E and foliar CK concentration, although these relationships varied among canopy layers. The relationships were strongest in the middle and lower canopy layers where there was less fluctuation in leaf water status and less variability in abiotic variables. The relationships between gas exchange parameters and leaf CK concentration began to decouple near the end of the growing season as foliar phytohormone concentrations changed with the approach of dormancy.     

Biological and sequence comparisons of Potato virus Y isolates associated with potato tuber necrotic ringspot disease

The biological and molecular relationships between a large number of Potato virus Y (PVY) isolates were examined, concentrating mainly on isolates associated with potato tuber necrotic ringspot disease (PTNRD). Following detailed analysis of the coat-protein gene, four main groups were identified which broadly corresponded to the phenotype of the different isolates. The groups comprised the ordinary strain (PVY^O), the necrotic strain (PVY^N), the C strain (PVY^C) and a group of recombinant (between ordinary and necrotic) isolates. In the latter group, all members were associated with PTNRD. However, four nonrecombinant isolates were also identified which were associated with PTNRD or tuber necrosis. Three were from tubers showing PTNRD symptoms in the field, while the fourth originated from symptomless tubers, but could cause necrotic rings on tubers under glasshouse conditions. The results show that although coat-protein recombination is always found associated with the PTNRD phenotype, some nonrecombinant isolates have very similar biological properties.     

Habitat use of a coastal delphinid population investigated using passive acoustic monitoring

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Effect of spraying techniques on the brown rot of peach fruit,and on black spot,powdery mildew and the two-spotted mite of apple trees

Application by hand-held equipment of the commercially recommended doses of proprietary formulations of captan (9.0 g a. i. per tree), mancozeb (10.8 g a. i. per tree), oxythioquinox (1.1 g a. i. per tree), and cyhexatin (1.8 g a. i. per tree), in spray volumes ranging from 0.225 to 9.0 litres per tree, gave commercial control of the brown rot of peach fruit, and of black spot (apple scab), powdery mildew and the two-spotted mite (Tetranychus urticae) of apple trees. Commercial control was also obtained using a quarter of the recommended doses when applied in 0.225 or 2.25 litres per tree. The residue of oxythioquinox on the leaves, immediately after applying 1.1 g a. i. per tree, doubled as the volume of spray was reduced from 9.0 to 2.25 litres per tree, and increased further when the volume was reduced to 0.225 litres per tree. It is suggested that some of the oxythioquinox ran off the trees at the higher volumes, and that less run-off at lower volumes resulted in higher chemical residues.     

The Canadian Cooperative Wildlife Health Centre and surveillance of wild animal diseases in Canada.

The Canadian Cooperative Wildlife Health Centre (CCWHC) was established in 1992 as an organization among Canada's 4 veterinary colleges, with a mandate to apply veterinary medicine to wildlife management and conservation in Canada. A major function of the CCWHC is nation-wide surveillance of wild animal diseases. Disease surveillance is conceived as consisting of 4 different activities: detection, diagnosis, information management, and use of information. In the CCWHC surveillance program, detection of disease is carried out by a wide range of professional and avocational field personnel, and much effort is expended to stimulate and support this activity. Diagnosis is done by personnel of provincial and federal veterinary laboratories and the CCWHC. Information management is achieved through a national database of wildlife disease incidents developed and maintained by the CCWHC. Use of information is enabled through established channels for distribution of information derived from the surveillance program to persons responsible for wildlife programs and policies, and to the public. There has been a high demand for the services of the CCWHC since its establishment. The CCWHC responds to approximately 2000 requests for information annually, distributes its newsletter to over 1700 recipients, examines approximately 1200 wild animal submissions each year, and has accumulated records of over 5000 disease incidents in its database. Technical information from the CCWHC has benefited federal, provincial/territorial, and nongovernment wildlife agencies; endangered species recovery programs; federal and provincial veterinary services; and federal and provincial public health programs.