Accumulation of (14)C from exogenous labelled auxin in lateral root primordia of intact pea seedlings (Pisum sativum L.).

When [(14)C]indol-3yl-acetic acid was applied to the apical bud of 5-day old dwarf pea seedlings which possessed unbranched primary roots, a small amount of (14)C was transported into the root system at a velocity of 11-14 mm h(-1). Most of the (14)C which entered the primary root accumulated in the young lateral root primordia, including the smallest detectable (20-30 mm from the primary root tip). In older (8-d old) seedlings in which the primary root bore well-developed lateral roots, (14)C also accumulated in the tertiary root primordia. In contrast, little (14)C was detected in the apical region of the primary root or, in older plants, in the apices of the lateral roots.