Studies of Rest Period. II. Nitrogen and Phosphorus Changes in Embryonic Organs of After-Ripening Cherry Seed.

Information on changes which occur during afterripening is essential to an understanding of the mechanism of the rest period. In the first paper of this series (7) we reported that during after-ripening growth occurs in the embryonic axis of the cherry seed. This growth is accompanied by translocation of materials from cotyledons to axis, an increase in respiration rate of the axis, and an increase in the efficiency with which the respiratory enzyme system is utilized. These data suggest that the respiratory rise might be due to an increased supply of available phosphate or phosphate acceptors. The present work was performed to test this hypothesis. The observations are divided into two parts: A, measurement of changes in total nitrogen and phosphorus in the embryonic axis during after-ripening, and B, fractionation of total phosphate and measurement of the changes in quantities of these fractions during afterripening. The results show that total phosphate concentration in the axis increases during after-ripening. This increase is not reflected uniformly in all fractions measured.