Nitsan, J., Plant Physiology Laboratory, Department of Agronomy, National and University Institute of Agriculture, Rehovot, Israel

MANY attempts have been made to relate the phenomena of vernalization to chemical entities, particularly macromolecular components, such as nucleic acids1, proteins2, and related substances3. The results so far obtained have been either negative or inconclusive. The present communication reports a successful demonstration of the accumulation of an electrophoretically homogeneous macromolecular component in the vernalized embryos (and seedlings) of Petkus winter rye (supplied by F. von Lochow, Petkus Co., Bergen, Germany). This component was greatly reduced by devernalization and was absent from non-vernalized embryos. © 1962 Nature Publishing Group.