摘要:

Peach production in Ontario is largely restricted to the Niagara Peninsula and Essex County, areas that are separated by some 200 miles but have a similar climate. The peach replant problem has been much more serious in Essex County than in the Niagara Peninsula. A survey of mature peach orchards showed thatPratylenchus penetrans(Cobb, 1917) Sher & Allen, 1953, is considerably more prevalent in peach soils in Essex County than in the Niagara Peninsula. In both areas, orchards that had a previous history of the replant problem had three to four times greater soil population ofP.penetransthan those with no such history. Soils of finer texture were shown to limit the populations ofP.penetrans, and the relatively low numbers of this nematode in the Niagara Peninsula appear to result from the influence of the finer soils prevailing in that region. The effect of different soil-particle sizes on the build-up ofP.penetransmay explain the distribution of the peach replant problem in Ontario.

ISSN:0008-4026    

DOI:10.1139/b58-011

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Further evidence was accumulated indicating that the peach replant disease decreases in severity as the interval increases in time between removal of the old orchard and the planting of new trees. The ameliorating effect of the interval may be related to the decline ofPratylenchus penetrans(Cobb, 1917) Sher & Allen, 1953. In experiments, increased growth of peach was associated with the control ofP.penetransby nematocides andP.penelranswas found to be the first nematode to attack newly developing peach roots. The populations ofP.penetranswithin such roots increased rapidly, then gradually declined. Generally, ectoparasites appeared later, increased relatively slowly, and occurred infrequently until late in the second growing season. The soils of all commercial peach nurseries in Ontario containP.penetransand the nematode may be transported in the roots of nursery stock.

ISSN:0008-4026    

DOI:10.1139/b58-012

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

Samples of peat from the Fort Churchill area in Manitoba have been investigatedin the hope that a quantitative system would be found to explain peatstructure. 'This entailed the developnlent of a method which would allow detailedstudy of the peat with the organic elements in their in situ position. Thequantitative results, categorized according to botanical relationships, were usedto indicate the structural differences in the samples studied, and also to elucidatethe vegetational succession of the samples. Relationships between subsurfacedetails and surface vegetation are discussed.

ISSN:0008-4026    

DOI:10.1139/b58-013

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

A survey of the keto acids of wheat showed α-ketoglutaric, pyruvic, glyoxylic, hydroxypyruvic, α-ketoisocaproic, oxaloacetic, and a number of unidentified keto acids to be present. The behavior of α-ketoglutarate, pyruvate, and glyoxylate in germinating seedlings under different conditions in light and dark and in aging leaves and in starving excised leaves was studied. These keto acids appeared and reached a peak during the early stages of germination. Oxaloacetic acid was present only in trace amounts. An unidentified keto acid was found to accumulate in etiolated seedlings. The effect of a nitrogen atmosphere on keto acid levels and the incorporation of glucose-C14into pyruvate, α-ketoglutarate, and oxaloacetate provided evidence for the operation of the tricarboxylic acid cycle in seedlings.

ISSN:0008-4026    

DOI:10.1139/b58-014

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

In order to determine the metabolic origin of glyoxylate 12 different carbon-14 labelled compounds, including sugars, organic acids, and amino acids, were fed to wheat tissue. With the exception of glycine none gave rise to glyoxylate. The labelling from glycine was slight and could not have accounted for the large amounts of glyoxylate in the tissue. Of a number of inactive compounds fed to degrained seedlings only allantoin induced an increase in the concentration of glyoxylate. A nitrogen atmosphere was found to increase the content of glyoxylate while decreasing that of allantoin. Allantoin-C14was synthesized much more readily from glycine-C14than from glyoxylate-C14. When seedlings previously fed glycine-C14in air were transferred to nitrogen, considerable radioactivity appeared in glyoxylate. These results suggest that glycine is a precursor and glyoxylic acid a hydrolysis product of allantoin.

ISSN:0008-4026    

DOI:10.1139/b58-015

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The moisture content in subalpine spruce was highest in overstory trees and lowest in understory trees, and it was higher in trees on a moist site than in trees of similar vigor classes on a dry site. Moisture contents of 10% of saturation for the more vigorous trees on the moist site and 7% of saturation for the less vigorous trees on the dry site represented a statistically significant difference which appeared to restrict the development of heartwood fungi to the wetter trees. A similar difference in the moisture content existed between the 1.5-ft. and the 20-ft. level of the trees, the occurrence of fungi being restricted to the wetter basal portion of the stems. In the laboratory, infection did not take place in test blocks at moisture contents lower than 8% of saturation. It is suggested that the threshold moisture content for infection in the trees occurs around the 7 to 8% saturation level. In the laboratory tests a difference in the moisture content of 3.4% of saturation in wood resulted in a statistically significant difference in the rate of decay byConiophora puteana(Schum. ex Fr.) Karst., but differences in ring frequency and specific gravity in the test pieces corresponding to the differences between these properties in the living trees did not appreciably affect the decay rate. There was no evidence that variations in the distribution of decay-promoting or decay-retarding substances occurred in the trees from the two sites.

ISSN:0008-4026    

DOI:10.1139/b58-016

出版商:NRC Research Press    

年代:1958

数据来源: NRC

ISSN:0008-4026    

DOI:10.1139/b58-017

出版商:NRC Research Press    

年代:1958

数据来源: NRC