1984 Volume 53 Issue 1 Pages 17-22
Buds, leaves and 2 to 3-year-old bark and wood were sampled from 21-year-old satsuma mandarin trees (Citrus unshiu Marc.) throughout the year and analysed for total nitrogen, 70% ethyl alcohol soluble and insoluble N, amino acids, mainly arginine and proline, and amides. Many nitrogenous components showed seasonal variations in their content. In old parts, it was the highest in April, the sprouting season, and the lowest in July, the final stage of new shoot development, while it was lowest in September in new leaves. Bark and wood showed temporary increases in the content of total and soluble N, free proline, and especially free arginine during the sprouting period from late March to mid April, and then declines in insoluble N. Buds, on the other hand, showed a marked decrease in proline together with a drastic increase in arginine during the sprouting period. These findings suggest that the soluble N components, such as proline and arginine, are used first for new shoot development, followed by the insoluble N. In old leaves, most of these components began to decrease in early May and the percentage decline of total N from early May to July was about 16% on a dry weight basis, about 40% of which was accounted for by the loss of free proline N. On the whole, all of these components increased in all parts of the tree from autumn to winter. The increases of proline in bark and leaves were particularly marked.