Induced Changes in Permeability of Plant Cell Membranes to Water

Z. Glinka^a

Leonora Reinhold^b

^a Department of Botany, Tel Aviv University, Tel Aviv, Israel, ^b Department of Botany, Hebrew University of Jerusalem, Jerusalem, Israel.

The half-time for THO equilibration was three times longer fora living carrot (Daucus carota L.) cylinder than for a deadone. Furthermore, the energy of activation of THO flux was morethan twice as high for the living cylinder. Passage throughliving membranes thus constitutes a rate-limiting step for THOflux in carrot tissue.

CO₂ increased the half-time (t) for THO equilibration. Treatmentwith abscisic acid or with tertiary butanol decreased t. Inneither case was the selective permeability of the membranedestroyed.

p-Chloromercuribenzoate and carbonyl cyanide m-chlorophenylhydrazone,if supplied together with abscisic acid or tertiary butanol,abolished their action. If abscisic acid or butanol was firstallowed to act alone, its effect was stable to subsequent treatmentwith the inhibitors. p-Chloromercuribenzoate and carbonyl cyanidem-chlorophenylhydrazone at concentrations at which they affectedabscisic acid and butanol action, did not influence THO fluxin control tissue. At considerably higher concentrations, however,2, 4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazoneraised t. The CO₂ effect was very rapidly reversible. Full reversalof the butanol effect required 3 hours, and that of abscisicacid required 4 days.