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The Fluctuation Curve of Sex Reversal in Staminate Hemp Plants Induced by Photoperiodicity

John H. Schaffner
American Journal of Botany
Vol. 18, No. 6 (Jun., 1931), pp. 424-430
Stable URL: http://www.jstor.org/stable/2435878
Page Count: 7
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The Fluctuation Curve of Sex Reversal in Staminate Hemp Plants Induced by Photoperiodicity
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Abstract

Taking advantage of the difference in length of daylight from July 15 to May 15, a series of bimonthly plantings, in the greenhouse, of Cannabis sativa was carried on in order to find out the fluctuation in sex reversal of staminate plants as induced by photoperiodicity. A very perfect fluctuation curve was developed, ranging from zero reversal for the July 15, May 1, and May 15 plantings to 100 percent reversal for the Nov. 1 and Nov. 15 plantings. There are no super-males in respect to reversal, since every staminate plant can be caused to express femaleness. The degrees of readiness or difficulty of reversal shown by different individuals are to be ascribed to degrees of differentiation, both physiological and morphological, which the individuals have attained. The determination of sex in the hemp is not caused by an allosome differential, but these chromosomes must be assumed to play a passive rôle. Determination is brought about through differential physiological states developed in gradients in both the egg and the vegetative body.

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