Summary
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1.
Infra-red radiation of wavelength approximately 1μ at an environmental temperature of 20° C, has been applied to meiotic prophase in Tradescantia bracteata—a clone with mainly terminally localised chiasmata being used.
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2.
Three hours treatment, with a recovery period of 21 hours, induces an increase in the frequency of interstitial chiasmata accompanied by a corresponding decrease in the number of terminal chiasmata.
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3.
Treatment of plants with low chiasma frequencies increases the number of terminal chiasmata only.
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4.
These increases may be due to decrease of viscosity in the nuclear sap which leads to more chromosome movement. Thus crossing-over nearer to the centromere is facilitated.
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5.
Similar increases in the frequency of interstitial chiasmata result from growing plants at a constant temperature of 20° C for eight days. This is presumably due to the introduction of stable physiological conditions.
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I am indebted to Mr. L. F. La Cour for his advice and criticism.
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Snoad, B. The action of infra-red upon chiasma formation. Chromosoma 7, 451–459 (1955). https://doi.org/10.1007/BF00329737
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DOI: https://doi.org/10.1007/BF00329737