Transport of benzyladenine and gibberellin A1 from roots in relation to the dominance between the axillary buds of pea (Pisum sativum) cotyledons

In etiolated, 5-day-old pea (Pisum sativum L.) seedlings a significantly more intensive growth of buds situated in the axil of the excised cotyledons was observed as early as 4 hours after decapitation and excision of one cotyledon of each pair. If [8-14C]benzyladenine ([14C]BA) was applied to roots of intact plants 10 hours prior to such decapitation and excision, significantly higher both total and specific 14C activities were observed in buds situated on the side of the excised cotyledons as early as 4 hours after decapitation and excision. Although the removal of a substantial part of the root system carried out simultaneously with decapitation and excision of one cotyledon resulted in a decrease in total 14C activity of buds, nevertheless a higher accumulation of 14C activity was maintained in buds situated on the side of excised cotyledon. If [14C]BA was applied to roots of seedlings after they were decapitated and deprived of one cotyledon, both total and specific 14C activities of buds situated on the side of excised cotyledons were significantly higher as early as the end of uptake of [14C]BA by roots, i.e. after 10 hours. On the other hand, [1,2-3H]gibberellin A1 applied to roots of intact and/or decapitated and one-cotyledon-deprived seedlings in the same way as [14C]BA did not appear in the buds until very much later and only in negligible amounts (i.e. 3H activity). This indicates that the release of buds from apical dominance represents an active and selective process which can result from the ability of buds to utilize and/or synthesize only certain growth substances within a certain time interval.