Abstract
Amino acids, amides and nitrate were determined in the xylem sap obtained by the vacuum extraction from sections of 2 to 3-year-old wood of 21-year-old satsuma mandarin trees (Citrus unshiu Marc.), and seasonal variations in their content were followed throughout the year. The main nitrogenous compounds identified were proline, arginine, asparagine and nitrate, all of which showed seasonal variations in their content. Proline showed a slight increase in April, the early stage of new shoot development, then a sharp decrease until early June, and again an increase from October to December. Arginine showed a similar seasonal variation to that of proline. Asparagine showed 2 peaks, one in mid May, the other in late July. Nitrate had a similar variation to that of asparagine. Other amino acids showed smaller variations compared with the above-mentioned compounds.
