Evidence for the acid-growth theory of fusicoccin action

✍ Scribed by U. Kutschera; P. Schopfer

• Publisher: Springer-Verlag
• Year: 1985
• Tongue: English
• Weight: 467 KB
• Volume: 163
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00392706

✦ Synopsis

Three predictions of the acid-growth theory of fusicoccin (FC) action in inducing cell elongation were reinvestigated using abraded segments of maize (Zea mays L.) coleoptiles, i) Quantitative comparison of segment elongation and medium-acidification kinetics measured in the same sample of tissue shows that these FC-induced processes are strictly correlated in time and respond coordinately to cations present in the medium, ii) Fusicoccin (1 gmol 1-1) induces a rapid acidification of the cell-wall solution, reaching a final level of pH 3.8-4.0. Exogenous protons are able to substitute quantitatively for FC in causing segment elongation at pH 3.8-4.0. At pH 4, FC has no additional effect on cell elongation, iii) Neutral buffers (pH 7) completely abolish the FC-mediated growth response, iv) Cycloheximide (10 mg 1-1) inhibits both FC-induced and acid-buffer(pH 4)-induced elongation after a lag of 40-45 min, and FCinduced H + excretion after a lag of 2 h. Under the same conditions, indole-3-acetic acid-induced elongation and H + excretion are inhibited without detectable lag. It is concluded that these results are fully compatible with the acid-growth theory of FC action.