TRANSPORT AND METABOLISM OF [H-3] ISO-PENTENYLADENINE FOLLOWING APPLICATION TO THE TIPS OF INTACT AND DECAPITATED TAP ROOTS OF PINUS-PINEA

[H-3]iso-Pentenyladenine ([H-3]iP) was fed for 24 h to the tips of intact and root tip-decapitated Pinus pinea seedlings. Twelve and 24 h after application to the roots of intact plants most of the applied radioactivity (+/-60%) was transported to the shoot. Root tip removal increased transport of the applied radioactivity to the shoot, but the overall pattern of distribution of radioactivity in the seedling did not change. Large amounts of radioactivity were recovered from the elongation zone of the root. Some radioactivity also accumulated in the older part of the root with well-developed lateral roots. When [H-3]iP was applied one day after decapitation, no significant changes in the pattern of radioactivity distribution were found between the intact and decapitated root systems. However, when applied 7 days after decapitation there was a significant increase of radioactivity in the region of the root where lateral roots were emerging. HPLC separation of extracts from the different root sections showed that [H-3]iP was extensively metabolized in the root. Six peaks of radioactivity, which co-chromatographed with authentic cytokinin standards, were detected.