Fig. 1.

(A, B) Influence of the medium on the time course of IAA diffusion out of excised shoot tips (diffusible IAA) from 10-day-old two-branched (2-B) and one-branched (1-B) pea seedlings. (C) Effect of defoliation on IAA export from shoots of 12-day-old 1-B plans. Schematic views of the experimental set-up for IAA export measurements is shown on the left. The 2-B plants were prepared by removing the epicotyl from 4-day-old seedlings to induce the growth of two axillary buds at the cotyledonary node. 1-B plants were then produced by removing one branch from 2-B plants at day 8 or 10. After 2 days, diffusible IAA from excised shoot tips of 10- or 12-day-old 2-B and 1-B plants was collected into 120–150 µl of aqueous medium stepwise during an incubation period of 2 h (A) or four 1 h periods (B, C), and IAA was measured by ELISA. Data are expressed as the mean ±SE of three samples pooled from six shoot diffusates. BA, 6-benzylaminopurine; K-Pi, potassium phosphate buffer.