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For almost a half century now, repeated failures in direct seeding operations on cutover forest lands in North America had been largely blamed on the unproven destruction of the seed supply by small mammals. In 1960, the Canadian Wildlife Service undertook a research project to ascertain the possible fate of white spruce seeds placed into the natural environment and the influence which small mammal populations may have upon such a seed supply. By equipping each seed with a microscopic radio-transmitter (radio isotopes), the seeds could be left in the field for up to one year and then recovered intact or as seed coat fragments to provide data on seed fate. Recovery success on 21,800 white spruce seeds in ten years of study has been 90%. Recoveries indicate near 50% of spring sown seeds could be destroyed by small mammals within 17 weeks in some years despite the fact that these seeds had been previously treated with the widely accepted protective coating of aluminum powder-endrin-arasan-latex. Late winter seeding reduced losses to small mammals by 2/3. No direct relationship between numbers of small mammals present and the number of seeds destroyed could be demonstrated. A critical examination of seed treatment procedures widely used has led to the development of a new seed coating formulation employing a potent rodent repellent, R-55. Under laboratory conditions, the new coating yielded improved germination and a high degree of protection against small mammals. The new coating treatment received limited field testing during 1969 and is currently undergoing refinement and more extensive laboratory and field testing in Alberta.

An index of tree growth based on the mean growth curve of black spruce shows that tree growth in the boreal forest of central Canada decreases linearly as the forest-tundra boundary is approached. A theoretical tree line is defined by black spruce growth data. The distribution of tree growth and the theoretical tree line indicate that the forest-tundra boundary is the mean summer position of the arctic front. The growth of white spruce is briefly considered, but because of a small sample size, no conclusions are drawn. [ABSTRACT FROM AUTHOR]

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The research explored the apparent contradiction between the cohesion-tension theory and the lack of blockage following freezing in conifers. Five to ten cm lengths of the main stem of actively transpiring Thuja occidentalis, Picea glauca and Pinus sylvestris were frozen. On thaw, there was no evidence of blockage in the formerly frozen xylem. Microscopic examination of frozen wood and hydrodynamic considerations showed that air was present in the xylem water and that bubbles were probably present upon freezing. On freezing about 9 per cent of the water irreversibly migrated into the unfrozen plant parts. Lack of blockage in the presence of air bubbles was reconciled to the cohesion-tension theory by a model in which only the largest bubble in a number of interconnected cells expands. As this bubble expands tension is released allowing all bubbles in adjoining tracheids to redissolve. Potential rate of resolution of unexpanded bubbles following release of tension was calculated to be less than 0.1 second. [ABSTRACT FROM AUTHOR]

A detailed study of the organic nutritional requirements for growth of a strain of cells derived from a tumor on Picea glauca has resulted in simplification of the earlier nutrient. The revised formula includes the standard salts of White's nutrient, 5 °A) sucrose. 0.25 Vo glutamine. 0.1 % inositol, and trace levels of thiamin, niacin, ascorbic acid, and 2.4-1). This formula will support uniform growth of this strain of cells at a rate of about 5-fold increase per 2-week passage. No consistent differentiation has been observed in any of the wide range of conditions tested. [ABSTRACT FROM AUTHOR]

Experiments aimed at simplification and improvement of procedure and establishment of an optimal routine for Spruce tumor cultures have resulted in the following regimen: One-ounce French square bottles charged with 9 ml of a 0.5 Vo agar medium; a single 20 mg culture per bottle; temperature 23°, darkness or diffuse light; a 2-week transfer cycle; a pH of about 5.5. [ABSTRACT FROM AUTHOR]

The effect of indoleacetic acid and of an auxin antagonist has been studied on tumorous and normal tissues of Picea glauca in culture. The cultures of tumor tissue would not grow in the absence of auxin, and eventually died. Normal tissues, on the other hand, grew equally well with or without added auxin. Furthermore, the auxin antagonist, p-chlorophenoxy-isobutyric acid, supplied at the same concentration as the IAA, strongly inhibited the growth of tumor tissue, while the growth of the normal tissue was unaffected. Mitoses were also decreased proportionately. These results confirm that the difference between the auxin relations of tumor and normal tissues of Picea glauca is the opposite of that for other such pairs of tissue in the literature. Finally, the simultaneous presence of both auxin and antagonist does permit some limited growth of the tumorous tissue with continued mitoses and without signs of abnormality. [ABSTRACT FROM AUTHOR]

Tissues of Picea glauca excised from the cambial region of the massive epiphytotic tumors characteristic of this species in certain regions, from non-tumorous portions of tumor-bearing trees and from trees not carrying evident tumors have been cultivated in vitro as continuous rapid growing cultures maintained on filter paper saturated with a complex defined liquid nutrient. The rapid blackening which regularly follows trauma of tissues with an active polyphenoloxydase system, as is true of many tree tissues, and which results in cessation of growth, could be overcome either by addition of tyrosine to the nutrient or by the use of phenoloxydase inhibitors such as diethyl-dithiocarbamate. These inhibitors were, however, only temporarily effective. Only tyrosine permitted continued growth. The auxine system appears to be closely associated with the polyphenoloxidase system and indole acetic acid was effective only at excessively high concentrations, being better replaced by 2.4-D. Tumor tissues, when they grew at all, consistently began growing more promptly than did normal tissues. There were, however, more frequent failures of tumor cultures and their responses to changes in nutrient or culture conditions were much more erratic than in the case of normal tissues. The presence of tumors did not effect the behavior of non-tumor tissues of tumor-bearing trees. Tumor tissues appeared to require Vitamin B12 which is not required by normal tissues. [ABSTRACT FROM AUTHOR]