Changes in histories during the vernalization of wheat embryos

The effect of cold-treatment on chromatin-histone in winterwheat embryos was studied. As the embryos were vernalized, theamount of whole histone increased about two-fold, but the histonecontent in excised embryos incubated in a medium containingsugar was changed little by prolonged chilling. These resultssuggest that the increase in histone content is not necessarilyconnected with the vernalizing response. Disc electrophoretic patterns of whole histone from vernalizedembryos gave a relatively distinct band of the faster movingcomponent of Fraction F-1 histone which was very scanty in non-vernalizedembryos but distinct in spring wheat embryos. Although therewas no increase in whole histone content, the faster-movingband of F-l was more conspicuous and bands of the other fractionswere fainter in the vernalized excised embryos. These observationssuggest that this particular component of Fraction F-l histoneis connected with the vernalizing response. As vernalization proceeded, the amino acid composition of wholehistone changed and the lysine-arginine ratio became higher,in agreement with the observed increase in the lysine-rich fraction(F-l) of histones. Nuclear size increased about two-fold during the period of vernalization,supporting the view that in embryos exposed to low temperature,cell division hardly proceeds. (Received September 27, 1972; )