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THE ACCURACY OF THE PLATE COUNT OF SUSPENSIONS OF PURE CULTURES OF BACTERIA IN STERILE SOIL |
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Canadian Journal of Research,
Volume 16c,
Issue 8,
1938,
Page 305-312
Marjorie Sutherland,
Norman James,
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摘要:
A culture ofPseudomonas fluorescenswas suspended in a sterile soil and water mixture. Dilutions of 1:2,000,000 and 1:10,000,000 were made immediately and plated in four replicates of each dilution, using nutrient agar. This was repeated 200 times. A χ2value was calculated from each set of four counts. The distribution of the 200 χ2values in the platings from each dilution agrees very well with the theoretical distribution. In a second experiment, 100 sets of four replicates ofPseudomonas fluorescenswere plated along with 100 ofBacterium globiformeand 100 of a mixture of the two cultures. The distribution of the χ2values in each of the three sets is such that the values may be considered to have been derived from populations distributed according to the Poisson series.The close conformity of the distribution of the actual χ2values to that of the expected in each of the five sets of data appears to indicate that the mean of four replicates is reliable as an estimate of the population in the dilution plated; and further, that the failure to obtain this conformity with soil flora is due to other causes than technique.
ISSN:1923-4287
DOI:10.1139/cjr38c-031
出版商:NRC Research Press
年代:1938
数据来源: NRC
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EFFECT OF PHYTOHORMONES ON SEEDS DAMAGED BY FORMALDEHYDE AND OTHER DISINFECTANTS |
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Canadian Journal of Research,
Volume 16c,
Issue 8,
1938,
Page 313-329
N. H. Grace,
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摘要:
Experiments with cereal seeds demonstrate that the reduction in germination and early growth resulting from formaldehyde treatment can be largely overcome by adding the phytohormones, 1-naphthylacetic acid or 3-indolylacetic acid, to the disinfecting solution. The optimum concentration of the hormone for individual varieties of cereals lies between 0.01 and 5 p.p.m. Similar effects were also obtained with hormones after copper sulphate and hot water treatments. The method appears to have practical possibilities, and may also be useful for comparing the physiological activities of different compounds.
ISSN:1923-4287
DOI:10.1139/cjr38c-032
出版商:NRC Research Press
年代:1938
数据来源: NRC
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