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

✍ Scribed by U. Kutschera; P. Schopfer

• Publisher: Springer-Verlag
• Year: 1986
• Tongue: English
• Weight: 863 KB
• Volume: 167
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00391229

✦ Synopsis

Plastic and elastic in-vitro extensibilities (Epl and Eol) 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 indole-3-acetic acid (IAA)-induced change of Epl (A Epl) is strictly correlated with the growth rate for a period of 3-4 h. Subsequently, 3 gpl 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 A 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 A 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 A Epb indicating that a further growth parameter is also involved in the inhibition of cell growth by CHI. 3 Ee~ is not affected by either IAA, ABA, or CHI. It is concluded that A Epl, as determined