The Effect of Restricted Germination during Vernalization on First Leaf Length of Winter Rye

SUMMARY Winter rye grain was vernalized, using the restricted moisture technique, at various temperatures and moisture levels and the relation between first-leaf blade length and the degree of vernalization analysed. There was an inverse relation between these two factors, but leaf length was influenced by both temperature and moisture level in a manner quite different from the effect on the vernalization temperatures and the major requirement for short-leaf production proved to be the period of restricted germination normally imposed during vernalization. Cell counts of the epidermis of the first leaf blade showed that the reduction in length was due to inhibition of the earliest phase of leaf extension growth. It is suggested that some growth-promoting substance in the embryo, possibly IAA, is broken down during the restricted germination period. When grain is sown this shortage impedes early leaf extension until the level is restored by synthesis or translocation.