Auxin transport and growth in intact roots of Vicia faba

• Published in: Plant and cell physiology 1976-12, Vol.17 (6), p.1329-1342
• Main Authors: Ohwaki, Yoriko, Tsurumi, Seiji
• Format: Article
• Language: English
• ISSN: 0032-0781; 1471-9053; 1471-9053
• DOI: 10.1093/oxfordjournals.pcp.a075396

Transport of IAA applied to the intact root of Vicia seedlings was investigated in relation to root growth. The root was treated at 3–4, 4–5 or 7–8 mm from the tip with a narrow ring of lanolin paste containing IAA or IAA-2-14C in growth or transport experiments, respectively. The growth process along the root axis was examined in every 1-mm part from the tip at 30 min, 1 or 4 hr intervals. The elongation zone of the control root was 1–9 mm from the tip. IAA treatment brought about no significant change in the growth of the region apical to the treated site, whereas distinct inhibition of growth occurred in the region basal to the treated site within 1 hr. The transport of radioactivity was observed in both acropetal and basipetal directions within 1 hr, but the latter predominated for 8 hr or more; the nearer to the tip the treatment site, the longer the predominance lasted. The velocities of acropetal and basipetal transport were estimated at about 4 and 8 mm/hr, respectively. Autoradiographs of transverse section of roots showed that basipetal transport occurred mainly through the outer part of the root, whereas acropetal transport occurred mainly through the inner part, the central cylinder. It may be concluded that the basipetally transported IAA which passed through the outer part of the root inhibited the elongation of the intact root.