摘要:

The respiratory behaviour of tomato fruits during their growth and ripening on the plant has been studied in relation to the season and light intensity during growth. Growth was found to be associated with an absolute increase in respiration rate. Fruits of all populations showed a marked rise and fall in respiration rate during ripening. This senescent drift was confirmed in detail by following the respiration of individual fruits ripening while still attached to the plant. Although exhibiting the usual senescent drift as they changed colour, fruits grown in summer cloth house plots showed a consistently lower rate of respiration than that observed in all other populations. It also has been shown that the chief path of gaseous exchange of the mature attached fruit is localized at the stem end.

ISSN:1923-4287    

DOI:10.1139/cjr42c-019

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Semimonthly collections of white pine and white spruce cuttings were taken from July to October, 1939, and propagated in several media. Collections of both species were taken in late October to examine the effect of type of cutting and of planting in media involving different proportions of two sands and two different peats. Cuttings were dusted with a series of concentrations of indolylacetic acid in talc. The season of collection and the medium used for propagation were the factors of main importance. Phytohormone treatment failed to demonstrate appreciable effect, no difference in rooting response could be attributed to the kind of sand used, but there were indications that response increased with the amount of sedge peat in the medium.Rooting of white pine cuttings collected in late August and propagated in a sedge peat medium was 62%, earlier and later collections gave substantially less rooting. Sand only and the sphagnum peat media were generally inferior to the sedge type of peat. At the optimum season of collection the sphagnum peat effected 50% rooting.The late July collection of white spruce cuttings effected rooting of 90% of the plain cuttings when propagation occurred in a sedge peat medium. Low percentages rooted in sand or sphagnum peat media. Cuttings with a heel of old wood tended to be superior to plain cuttings in respect to survival and rooting.Preliminary experiments with spring and early summer collections of both species resulted in slight rooting. Likewise, greenhouse propagations of dormant material gave very poor results.

ISSN:1923-4287    

DOI:10.1139/cjr42c-020

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Data for 14 yr. were used to determine the average effect of rainfall on the protein content of wheat grown at seven stations in the dry belt of southwestern Saskatchewan. Employing the concept of a regressional integral, and working with the rainfall for consecutive five-day intervals from April 1 to August 3, a curve was obtained which represents the change occurring during the growing season in the average regression coefficient (i.e., the average unit decrease in protein content per unit increase in rainfall). It was found that 34% of the residual variance for protein content can be ascribed to variations in rainfall. Above average rainfall during the growing season generally tends to reduce protein content, but this tendency is much more marked during April and early May, and during the latter part of July. These are also the periods during which average rainfall is lowest. The effect on protein content of precipitation occurring during the previous fall is of minor importance.

ISSN:1923-4287    

DOI:10.1139/cjr42c-021

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Samples of frozen subsoil were obtained aseptically at Churchill, Man., located on Hudson Bay at about 58° north latitude. These were cultured on various media. The procedure followed failed to demonstrate the presence of viable micro-organisms in the permanently frozen zone of a clay subsoil. Bacteria were isolated from samples obtained as deep as nine feet from the surface of a coarse gravel subsoil.

ISSN:1923-4287    

DOI:10.1139/cjr42c-022

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Significantly higher water contents are found in short samples of twigs isolated by simultaneous cuts than in samples isolated by consecutive cuts in which displacement of water obviously takes place. This is in agreement with the results of McDermott. Natural water gradients are small and do not invalidate McDermott's figures. Displacement is not confined to the immediate neighbourhood of the cut.

ISSN:1923-4287    

DOI:10.1139/cjr42c-023

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Root rot of corn in Ontario is caused primarily by parasitic soil micro-organisms, the most important of which are species ofPythium,Helminthosporium, andFusariumin that order. The disease causes a decrease in the stand by pre-emergence killing and a dwarfing of the plants by the parasitic invasion and destruction of their roots by the organisms. The pathogens have different optimum soil temperatures but the lower ranges favour those that cause the most severe damage. The roots of other field crops can be parasitized by the organisms found associated with corn root rot, but their effect on the development of the crop varies greatly. It has been proved under greenhouse conditions that the severity of the disease is greatly reduced if the corn is preceded by cover crops of soybeans and materially increased when preceded by timothy. Other crops tested have an intermediate effect.

ISSN:1923-4287    

DOI:10.1139/cjr42c-024

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

The structure and development of somatic spirals in microspore chromosomes ofTrilliumhave been investigated. The chromonemata in each metaphase chromatid and each anaphase chromosome form a large-gyred, hollow spiral. This spiral develops gradually during prophase by an increase in gyre diameter and a decrease in gyre number and in chromatid length. Its development is associated with theeliminationnot theproductionof chromatid relational coiling. At later stages an irregular waviness or "minor" somatic spiral is visible along its "major" gyres in which reversals of direction can also be discerned. Where the spiral can be seen to be double-stranded it is plectonemic (as early as mid-prophase).The prophase to metaphase chromatid contraction ratio is not less than 6:1. Mean chromonema length increases from 650 ± 17.2 at metaphase to 977 ± 28.3 at anaphase. This latter length is approximately that estimated for early meiotic prophase. Chromosome volume also increases (about twofold) during the interval between metaphase and anaphase. Mean chromonema length and gyre number in microspore anaphase chromosomes are more than twice as great as those of meiotic anaphase chromosomes. Since the chromosomes at these stages are of approximately the same mean length the gyres of the somatic spiral are thus more tightly "packed".InTrillium, microspore anaphase chromosomes are considered to be of essentially the same spiral structure as meiotic second division chromosomes, i.e., a single coil (butnotsingle-stranded), rather than two or more independently coiled chromatids. The process of reducing this plectonemic spiral into parallel, freely-separable chromatids begins in one prophase as a reduction in gyre number and continues as relational uncoiling in the next. Paradoxically, therefore, a spiralization cycle such as that described above can be interpreted as an uncoiling process in which successive cycles overlap in prophase.

ISSN:1923-4287    

DOI:10.1139/cjr42c-025

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Seven different reciprocal chromosome translocations involving six of the seven haploid chromosomes ofTriticum monococcumhave been studied in all possible heterozygous combinations. Plants with one complex of four chromosomes show only 5 to 10% sterility; those with two complexes of four, 10 to 20%; those with one complex of six, 20 to 30%. Completely random segregation in such types should cause 66.6, 88.8, and 90% sterility, respectively, while segregation directed only by the necessity that homologous centromeres go to opposite poles should cause 50, 75, and 75%, respectively. The very low sterility of translocation heterozygotes in wheat, as compared with these expectations, and with results reported in maize and other plants, is due to the fact that segregation is usually alternate (disjunctional) in complexes both of four and six.The forces of repulsion operating at metaphase are not restricted to the centromere but involve the whole body of the chromosome. In the absence of complicating features this naturally results in alternate segregation in complexes. Semisterility is due, not to basically random segregation, but to special conditions such as interstitial chiasmata, early opening of the complex, and crossing over between the centromere and the point of interchange. The latter is favoured by a non-median position of the centromere, great length of chromosomes, and shortness of at least one interchanged segment. The 50% sterility usually reported for translocations has no special significance; no particular percentage is characteristic of translocations in general.In complexes of six, double-cross configurations are more numerous than stars, and present many variations in form depending on the length and position of the segments exchanged. Additional factors producing sterility in large complexes are unwieldiness and crossing over in the segment that joins the two crosses.

ISSN:1923-4287    

DOI:10.1139/cjr42c-026

出版商:NRC Research Press    

年代:1942

数据来源: NRC