Involvement of auxin and cytokinins in initiation of growth of isolated pea buds

Axillary buds from the second primary scale excised from 21-day-old pea(Pisum sativum L. cv. Vladan) plants were used as a modelsystem for studying the release of buds from apical dominance. The isolatedbudswere transferred onto basal medium with or without a supplement of growthregulators and cultivated up to 24 h in short-term and up to 4weeks in long-term experiments. In both sets of experiments endogenous IAA,cytokinins and the uptake of labelled zeatin were analysed. The development ofbuds was monitored by image analysis, estimation of their weight, and byanatomical studies. Generative meristems were found in isolated axillary budsalready in 21-day-old plants at the beginning of the experimental period. Theonset of bud growth was recorded as soon as 2 h after the budexcision by image analysis. The bud growth was accompanied by a rapid transientincrease of the endogenous IAA level within the first 2 h,followedby an increase of iPA within 24 h. The uptake of the exogenouscytokinin ([^sup 3^H]Z) reached its peak between the 6 and 8hafter the release from apical dominance. The cytokinin analyses of bothshort-term and long-term bud cultures revealed the increase of free cytokininsand their glucosides, indicating de novo synthesis ofcytokinins in the buds themselves.[PUBLICATION ABSTRACT]