Vernalization in Cheiranthus allionii Hort.

The effect of vernalization in Cheiranthus allionii, a qualitative winter annual requiring cold, was studied in relation to external conditions, particularly temperature and day length. Both seed and plant vernalization may lead to flower formation. However, the vernalizability varied with the plant's age. There was a close relation between age, duration of vernalization and daylength after vernalization. In long days after vernalization seeds and older plants were most sensitive to vernalization, young plants being less sensitive. Short days after vernalization of either seeds or young plants diminished the effectiveness of vernalization but this disadvantageous effect was partly overcome by vernalizing for longer. Mature plants were day neutral after vernalization. Warmth (35°C) immediately after vernalization caused devernalization. However, warmth immediately before vernalization antagonized vernalization.

Only vernalized growing points and those derived from vernalized tissue attained a vernalized state.

The mechanism of vernalization was discussed in the light of the results with Cheiranthus allionii and the different published theories. It was concluded that the immediate product of vernalization was immobile.