¹⁴C‐Studies on Apple Trees III. The Influence of Season on Storage and Mobilization of Labelled Compounds

The present paper reports an attempt to elucidate the storage and mobilization processes in 1‐year‐old apple rootstocks by studying the 14 C content of different parts of the tree following application of 14 CO 2 . The translocation of the 14 C taken up from the leaves to other parts proceeds at the highest rate during the first few days after the application of 14 C. The distribution in shoots, trunk and roots after application of 14 C during May, July, August, and in part of September depends in particular upon the intensity of growth in the various parts. From the lime of the application of 14 C until leaf‐fall, 40–50 per cent of the 14 C initially absorbed disappears from the tree. After exposure to 14 C during October, and in part of September, a relatively large part of the 14 C applied goes to the root. In this case there is a considerable reduction in the 14 C‐conlent from leaf‐fall to the following spring after leafing, especially in the root, although relatively speaking reduction is also considerable in the bark of the parts above ground, and it is most pronounced in the methanol (80 %) soluble fraction. The reduction takes place primarily during spring, and comprises, after application during October, for the whole tree 20–25 per cent of the 14 C initially absorbed. Only 13–17 per cent of this amount was recovered in the newly developed shoots and leaves in the following June.