Effect of auxin and abscisic acid on cell wall extensibility in maize coleoptiles

• Published in: Planta 1986-04, Vol.167 (4), p.527-535
• Main Authors: Kutschera, U. (Freiburg Univ. (Germany, F.R.). Biologisches Institut 2), Schopfer, P
• Format: Article
• Language: English
• Subjects: ABA; Abscisin; ACIDE ABSCISSIQUE; ACIDO ABSCISICO; Agronomy. Soil science and plant productions; Auxin; AUXINAS; AUXINE; AUXINS; Biological and medical sciences; Cell growth; CELL WALLS; Chemical agents; CHEMICOPHYSICAL PROPERTIES; Coleoptiles; Corn; Creep tests; Dehnungsfaehigkeit; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Growth and development; Growth regulators; Kinetics; Koleoptyle; PARED CELULAR; PAROI CELLULAIRE; physik. Merkmal; Plant physiology and development; Plant tissues; Plants; PLANTULAS; PLANTULE; PROPIEDADES FISICO-QUIMICAS; PROPRIETE PHYSICO-CHIMIQUE; Saemling; SEEDLINGS; Turgor pressure; Vegetative apparatus, growth and morphogenesis. Senescence; Wachstumsregulator; Zea; ZEA MAYS; Zellwachstum; Zellwand
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/BF00391229

Plastic and elastic in-vitro extensibilities (Epl and Eel) of cell walls from growing maize (Zea mays L.) coleoptile segments were measured by stretching frozen-thawed tissue, pre-extended to its in-vivo length, at constant force (creep test) in a custom-buildt extensiometer, equipped with a linear-displacement transducer. The indol-3-acetic acid (IAA)-induced change of Epl (Δ Epl) is strictly correlated with the growth rate for a period of 3—4 h. Subsequently, Δ Epl remains constant while the growth rate is slowing down. Since this discrepancy can be accounted for by a growth-dependent reduction of osmotic pressure, it is concluded that Δ Epl represents quantitatively the relative increase of in-vivo extensibility (cell wall loosening) involved in IAA-mediated cell growth over a much longer time. On the other side it is argued that the growth rate may not be strictly correlated with wall extensibility during long-term growth. Abscisic acid (ABA) inhibits segment growth induced by auxin, fusicoccin, or exogenous acid, and this effect can be quantitatively attributed to an ABA-mediated reduction of cell wall extensibility as determined by the Δ Epl measurement. Both, IAA and ABA have no effect on total protein synthesis, RNA synthesis, and amount of osmotic solutes. Fusicoccin-induced proton excretion is only slightly inhibited by ABA. In contrast to ABA, growth inhibition by cycloheximide (CHI) is always much larger than the concomitant reduction of Δ Epl, indicating that a further growth parameter is also involved in the inhibition of cell growth by CHI. Δ Eel is not affected by either IAA, ABA, or CHI. It is concluded that Δ Epl, as determined by the applied method, represents a relative measure of the actual in-vivo extensibility of the growing cell wall at the very moment when the tissue is killed, rather than an average extensibility accumulated over some immediate-past period of time as suggested by Cleland (1984, Planta 160, 514—520). Hence, we further draw the conclusion that IAA and ABA control of cell growth can entirely be attributed to a modulation of cell wall extensibility by these hormones in maize coleoptiles.