Biologisches Institut II der Universität, Schänzlestrasse 1, D-7800, Freiburg, Federal Republic of Germany.
Planta. 1985 Apr;163(4):494-9. doi: 10.1007/BF00392706.
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 μmol l(-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 l(-1)) inhibits both FC-induced and acid-buffer(pH 4)-induced elongation after a lag of 40-45 min, and FC-induced 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.
三项关于激动素（FC）诱导细胞伸长作用的酸生长理论的预测，使用玉米（Zea mays L.）胚芽鞘磨损片段进行了重新研究。i）在同一组织样本中测量的片段伸长和介质酸化动力学的定量比较表明，这些 FC 诱导的过程在时间上严格相关，并协调响应介质中存在的阳离子。ii）FC（1 μmol l（-1））诱导细胞壁溶液快速酸化，达到最终 pH 3.8-4.0。外源性质子能够在 pH 3.8-4.0 下定量替代 FC 引起片段伸长。在 pH 4 下，FC 对细胞伸长没有额外的影响。iii）中性缓冲液（pH 7）完全消除了 FC 介导的生长反应。iv）环己酰亚胺（10 mg l（-1））在 40-45 分钟的滞后后抑制 FC 诱导和酸缓冲液（pH 4）诱导的伸长，以及在 2 小时的滞后后抑制 FC 诱导的 H（+）排泄。在相同条件下，吲哚-3-乙酸诱导的伸长和 H（+）排泄抑制没有可检测的滞后。结论是，这些结果完全符合 FC 作用的酸生长理论。
