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The pH profile for acid-induced elongation of coleoptile and epicotyl sections is consistent with the acid-growth theoryThe acid-growth theory predicts that a solution with a pH identical to that of the apoplast of auxin-treated tissues (4.5.-5.0) should induce elongation at a rate comparable to that of auxin. Different pH profiles for elongation have been obtained, however, depending on the type of pretreatment between harvest of the sections and the start of the pH-incubations. To determine the acid sensitivity under in vivo conditions, oat (Avena sativa L.) coleoptile, maize (Zea mays L.) coleoptile and pea (Pisum sativum L.) epicotyl sections were abraded so that exogenous buffers could penetrate the free space, and placed in buffered solutions of pH 3.5-6.5 without any preincubation. The extension, without auxin, was measured over the first 3 h. Experiments conducted in three laboratories produced similar results. For all three species, sections placed in buffer without pretreatment elongated at least threefold faster at pH 5.0 than at 6.0 or 6.5, and the rate elongation at pH 5.0 was comparable to that induced by auxin. Pretreatment of abraded sections with pH-6.5 buffer or distilled water adjusted to pH 6.5 or above gave similar results. We conclude that the pH present in the apoplast of auxin-treated coleoptile and stems is sufficiently low to account for the initial growth response to auxin.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Cleland, R. E. (University of Washington Seattle 98195, United States)
Buckley, G.
Nowbar, S.
Lew, N. M.
Stinemetz, C.
Evans, M. L.
Rayle, D. L.
Date Acquired
August 21, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Planta
Volume: 186
ISSN: 0032-0935
Subject Category
Life Sciences (General)
Funding Number(s)
Distribution Limits
NASA Discipline Plant Biology
NASA Discipline Number 40-50
Non-NASA Center
NASA Program Space Biology