摘要:

The degree of resistance to a pulsed electric current of wood in progressive stages of discoloration and decay in living trees was correlated primarily with the moisture and mineral contents of the wood. Below the fiber saturation point, the degree of resistance was correlated primarily with the amount of moisture while above the fiber saturation point resistance was correlated primarily with the concentration of mobile potassium and calcium ions. The apparatus used to produce the current and to measure the resistance to it was accurate in detecting and in indicating the stage of deterioration of discolored and decayed wood. The apparatus was tested and found to be reliable electrically within the range of resistances encountered in the trees studied.

ISSN:0045-5067    

DOI:10.1139/x72-039

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Effects of deicing salt on eastern white pine (PinusstrobusL.) were studied in the field and in the laboratory. Studies in controlled temperature chambers showed that solutions of deicing salt sprayed onto 4-year-old trees induced symptoms of foliar browning similar to those observed on trees growing near highways. Symptoms developed at 15 °C but not at 1.5 °C. The amount of injury that developed after 3 weeks at 15 °C appeared to be directly related to the concentration of sodium and chloride in the leaf tissue. Repeated sampling of foliage from trees adjacent to highway 401 between May 1970 and May 1971 revealed that foliar concentrations of sodium and chloride declined from abnormally high values (up to 1%) in May to 'normal' levels (0.02–0.1%) by August. The rate of loss was proportional to the foliar concentration of these ions. Growth of these trees, measured as bud weight, needle length, needle dry weight, needle bundles per leader, and leaf length, was suppressed on the side of trees exposed to the highway, but this suppression diminished as distance from the highway increased. Annual radial increments to the trunk were appreciably smaller in trees close to the highway than in trees further away. These results support the concept that deicing salt spray injures leaves and reduces growth of eastern white pine growing adjacent to highways that receive deicing salt in the winter.

ISSN:0045-5067    

DOI:10.1139/x72-040

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Tissue digestibility, essential oils, and levels of several chemical constituents were compared in foliage of Douglas-fir. Genotypes with different susceptibilities to deer browsing were used, and foliage was collected during the dormant season. In general, clones resistant to deer browsing had lower dry-matter and cellulose digestibilities, essential oils with greater inhibitory action on rumen microbial activity, higher content of fats, total phenols, flavanols, and leucoanthocyanins, and lower levels of chlorogenic acid. Results suggest that these resistance characteristics, especially the chlorogenic acid content, might be used instead of conventional bioassays with captive deer, to screen Douglas-fir breeding stock for resistance to deer browsing.

ISSN:0045-5067    

DOI:10.1139/x72-041

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Coating Douglas-fir and western hemlock seeds with R-55, a rodent repellent, seriously reduced normal germination. Acidifying the latex sticker, or adding graphite powder, had no effect. If seeds were coated first with latex, more R-55 could be applied without significantly increasing germination losses. Both stratification and dry storage of R-55 coated seeds increased germination losses. Treatment differences detected by normal germination percentages were also reflected in germination values. Observations based on total (normal + abnormal) germination obscured the effects of the various coatings.

ISSN:0045-5067    

DOI:10.1139/x72-042

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Analysis of peroxidase isoenzymes in interspecific elm hybrids indicated that a close correlation exists between parental isoenzymes and those of the progeny. In some crosses, isoenzymes undergo mendelian segregation while in others segregation distortion is evident. Mechanisms proposed to account for the disturbed segregation ratios and unexpected phenotypes include crossing over between peroxidase loci, accumulation of lethal genetic deficiencies, and dominance of some peroxidase genes.

ISSN:0045-5067    

DOI:10.1139/x72-043

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Rates of formation were measured for the base-catalyzed condensation reactions occurring between 4-alkylguaiacol compounds and their 6-methylol derivatives over the temperature range 85.5–100 °C. It was found that both the intercondensation reaction between the 4-alkylguaiacol compound and its 6-methylol derivative and the self-condensation reaction of the latter compound occurred at significant rates. In the 4-propylguaiacol – 4-methyl-6-methylolguaiacol system, the above two condensation reactions occurring in this system had the same activation energies, 35 kcal/mol. Similarly, in the 4-methylguaiacol – 4-propyl-6-methylolguaiacol system these two condensation reactions had equivalent activation energies, but slightly lower than in the former system, 32 kcal/mol. The kinetic results found for the model guaiacol compounds in this study demonstrate the possibility that a lignin-derived compound having more than one reactive position can be developed into a phenolic-type resin.

ISSN:0045-5067    

DOI:10.1139/x72-044

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The rocky heathlands of western Nova Scotia cover some 31 000 ha of coarse, bouldery ortstein podzol of granitic origin. The shrubby vegetation, dominated byGaylussaciabaccata, is closely correlated with topographic position and depth of soil over the impenetrable pan.Pollen analysis suggests that the area has, for many centuries, been a very open woodland and that the present community is a reflection of soil poverty as well as of periodic burning.Because the site is so unproductive it is suggested that wilderness recreation is the best land use.

ISSN:0045-5067    

DOI:10.1139/x72-045

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Twenty-six peat plateaus and eight palsas were examined near Flin Flon, Manitoba at the southern limit of discontinuous permafrost. Peat plateaus in different developmental stages were identified on the basis of their morphology. The permafrost is entirely within the peat in all peat plateaus within the study area, but extends into mineral subsoil under all palsas examined. Doming in peat plateaus is largely explained by volume change due to change from unfrozen to frozen stage, and by buoyancy of the frozen mass floating on unfrozen peat. The occurrence of aggrading and degrading peat plateaus in the same area indicates that all developmental stages are permitted by the present climate.

ISSN:0045-5067    

DOI:10.1139/x72-046

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Resistance in seedlings ofPinusarmandiiFranch. toCronartiumribicolaJ. C. Fisch. ex Rabenh. was high (ca. 72%). Resistance of artificially inoculated seedlings was expressed as: a percentage of seedlings lacking foliar or stem symptoms; a percentage of seedlings with foliar symptoms but lacking stem symptoms; or as a percentage of seedlings having bark reactions that were lethal to the fungus. Histological examinations indicated that the bark reactions resulted from necrosis of host cells which was apparently triggered by invading mycelium. Subsequent formation of a wound-periderm layer established a barrier between the diseased and healthy portions of the stem. Mechanisms providing resistance toC.ribicolainP.armandiiwere compared to such mechanisms inPinusmonticola(Dougl.) and other pines in response to infection by stem rusts; they were found to be strikingly similar.

ISSN:0045-5067    

DOI:10.1139/x72-047

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Ultrastructural observations on the foliar cells ofPopulusdeltoidesspp.angulataAit. infected by poplar mosaic virus revealed a high content of virus particles in the cytoplasm of most but not all young cells from chlorotic areas. Mature cells from necrotic areas contained far fewer virions while in symptomless green portions no virions were observed. Virus particles were not found in mature sieve elements or in mature nonliving xylem cells.Changes in the cytoplasm and in chloroplasts were followed. Healthy, mature chloroplasts contained well developed thylakoid systems. In infected cells, a disintegrative process at necrotization resulted in the dissolution of the thylakoid system into individual electron dense sacs which were released when the chloroplast membrane dissolved. Cytoplasmic changes were characterized by increased vacuolation. Cisternae of the endoplasmic reticulum and vesiculate bodies were also more numerous. Necrotization was accompanied by dissolution of the cell organelles.

ISSN:0045-5067    

DOI:10.1139/x72-048

出版商:NRC Research Press    

年代:1972

数据来源: NRC