摘要:

Leaves of cottonwood (Populusdeltoides, Bartr.) plants grown under constant conditions are initiated at relatively uniform rates. Because of this uniformity, the plastochron index (PI), developed by Erickson and Michelini (1957), can be applied to quantitatively identify the developmental stage of the vegetative shoot. In a preliminary test, the PI was shown to be linearly related to time, with plastochron intervals ranging from 2.00 to 2.76 days. In a second test, leaf plastochron indexes (LPI) were calculated for a series of trees representing five size classes. Statistical models were developed for each size class, relating each of the dependent variables (leaf length, leaf area, leaf dry weight, number of vessels per internode, and number of vessels per petiole) to LPI. These models were used to demonstrate that the PI and LPI can serve two useful purposes when applied to developmental studies of woody plants: (1) to adjust plants of different developmental stages to a standardized morphological time scale, and (2) to predict developmental processes and events from simple, nondestructive measurements.

ISSN:0045-5067    

DOI:10.1139/x71-001

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Mature pollen grains of lodgepole pine (PinuscontortaDougl.) were incubated in solutions of sucrose, indoleacetic acid (IAA), and stock solution A containing boric acid, calcium nitrate, magnesium sulfate, and potassium nitrate. Sucrose solution did not stimulate pollen germination but did inhibit pollen tube growth. A slight promotion of tube growth resulted from an IAA solution, but no increase was obtained in germination percentage. Stock solution B (diluted one-tenth of concentration of stock solution A) was optimum for pollen germination and pollen tube growth. Two basic types of pollen tube development and pollen tube branching occurred. An abnormal development of the pollen tube, protruding through the saccus, was recorded. After 5 days of incubation in stock solution B, the generative cell divided into the stalk cell and the body cell, and 2 days later the body nucleus divided to form two male nuclei of either equal or unequal sizes.

ISSN:0045-5067    

DOI:10.1139/x71-002

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

This paper presents results of measurements, made separately for each of four canopy layers, of throughfall and stemflow in a multilayered stand of largetooth aspen (Populus grandidentataMichx.). Each canopy layer is identified by the predominant woody or fern species. Equations describe relationships between stemflow, stem size, and storm size, and between throughfall and storm size. In general, stemflow per stem per storm increased as both stem size and storm size increased, the latter having the greater effect. The equations varied with species. General stemflow equations were constructed to calculate stemflow per stem per storm for tree sizes and storm sizes within the measured range. Throughfall per storm increased as storm size increased, but at different rates for different canopy layers. Monthly budgets of interception, stemflow, and net rainfall for the various canopies, separately and together, were computed for the summer months of 1969 using the stemflow and throughfall equations, measured gross rainfall during all summer storms, and data on canopy structure for four plots within the stand. Interception by all canopies together amounted to 22 to 46% of monthly gross rainfall. Interception from the bracken fern canopy alone was 3 to 9%. Stemflow was about 8 to 17% of the monthly gross rainfall. The highest proportion of total stemflow was from bracken fern. Net rainfall was 54 to 78% of the monthly gross rainfall.

ISSN:0045-5067    

DOI:10.1139/x71-003

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Because of the large volumes of decayed western hemlock wood available in British Columbia forests a small laboratory study was undertaken to assess the potential quantity of cellulose available from western hemlock wood decayed byEchinodontiumtinctorium. Alpha cellulose and holocellulose yields were determined for a total of 57 wood samples from five trees. On the basis of these limited investigations it appears that holocellulose and alpha cellulose yields from western hemlock wood decayed byE.tinctoriumshould be nearly equivalent to yields obtained from equal volumes of soundwood. Further investigation of cellulose yields from decayed wood is warranted.

ISSN:0045-5067    

DOI:10.1139/x71-004

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Newly dispersed seeds, established infections, and individually tagged shoots of hemlock dwarf mistletoe on western hemlock and shore pine, and established infections and individual shoots of larch mistletoe on western larch were examined periodically for up to 7 years, Infections on hemlock first appeared as swellings, some of which were visible during the first year after seed dispersal. Aerial shoots appeared in the second year. By the end of the third year most infections exhibited both swellings and aerial shoots. On all three hosts, mature mistletoe fruit were produced occasionally in the fourth year but generally not until the fifth year. Most female aerial shoots bore at least one crop of flowers during their existence, however, only half produced mature fruit. Aerial shoots varied in their life span from less than 1 year up to 7 years. The average was 2 to 3 years. One female shoot on larch bore five successive crops of flowers. The fastest longitudinal growth of mistletoe endophytic system occurred on western larch and the slowest was on shore pine. All infections were nonsystemic in that the endophytic system was largely confined to the swollen portions of the hosts.

ISSN:0045-5067    

DOI:10.1139/x71-005

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

In this study, effects of knots on cutting forces in sawmilling, cuts were made perpendicular to the grain in wood above 32% moisture content in order to simulate the action of band saw teeth. An apparatus with a single tooth was used. In white pine (Pinusstrobus) and red pine (Pinusresinosa), the main cutting force is greater when the growth rings are oriented tangentially than when they are oriented radially. In yellow birch (Betulaalleghaniensis), the principal force is greatest in the case of radial orientation. Wood with a specific gravity of 0.70 requires almost twice the principal cutting force of that required for wood with a specific gravity of 0.38. We have discovered that, in comparison with normal wood, medium compression wood of white spruce (Piceaglauca) brings about an increase of 35% in the principal cutting force. When a knot is cut, the principal force is approximately the same for the hardwood and softwood species studied. Because this is not the case in clear wood, the knot of a softwood such as white spruce requires approximately four times the principal force as that in clear wood. The knot of a hardwood such as the sugar maple (Acersaccharum) requires almost twice the clear wood principal force. Occasionally peak lateral forces equal to the principal cutting force in clear wood will cause a tooth to deviate in the immediate vicinity of a knot. It has been demonstrated that, in the case of a band saw, a deviation of at least 5 mm in the kerf may result. If the knot is at all large, it is obvious that several successive teeth must cut through it and the deviation of the blade will thus be greater. The losses through subsequent planing, necessary to correct the sawn surface, will thus be considerable.

ISSN:0045-5067    

DOI:10.1139/x71-006

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Low temperature or low light intensity following germination ofPinusresinosaseeds greatly suppressed subsequent seedling development, with cotyledon expansion inhibited more than root expansion. A strong influence of shoot environment early in ontogeny was demonstrated on initiation of all but a few early-formed primary needle primordia and on expansion of all primary needles, including those formed early. Low temperatures or low light intensities during the cotyledon stage of development prevented initiation of most of the normal complement of primary needles. However, when seedlings were placed in a favorable environment following prolonged exposure to low temperature or low light intensity, primordia of primary needles formed readily and subsequently expanded. Following seed germination, the young seedling is a system of competing carbohydrate sinks. Early development of the seedling is an integrated continuum with the source of growth requirements shifting during ontogeny, from megagametophytes to cotyledons, to primary needles, to secondary needles. The importance of cotyledons and primary needles to early seedling development is emphasized.

ISSN:0045-5067    

DOI:10.1139/x71-007

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A slow release form of the insecticide 2,2-dichlorovinyldimethylphosphate was tested to determine if it would protect developing strobili and cones ofPiceaspp. enclosed in pollination bags. A single, small chip (1 × 1 × 0.5 cm) of polyvinylchloride impregnated with the insecticide was placed in each pollination bag when the strobili were isolated. Cone damage by the spruce budworm and spruce coneworm was reduced from 85% to less than 10% in bags containing the insecticide. No phytotoxic effects were observed.

ISSN:0045-5067    

DOI:10.1139/x71-008

出版商:NRC Research Press    

年代:1971

数据来源: NRC