Root Research

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A possibility has been suggested on the signal transmission from leaves via change in xylem pressure to the root xylem proton pump playing key role in the active acropetal transport of water (Okamoto, 2010). In order to test this hypothesis, a new experimental set-up has been constructed to detect the change in trans-root electric potential (TRP) of tree-seedlings, evoked by the hydraulic pressure applied artificially to their xylem. Positive shifts in TRP (20~160mV) were detected by the application of the hydraulic pressure (10~80kPa) to the xylem of several kinds of tree seedlings. This electric phenomenon was not the transient such as action potential or variation potential, because it was the shift in resting potential level that continued during the application of the pressure. Therefore it means the activation of the xylem proton pump, since this reaction was inhibited largely by the application of DCCD (5×10^-4M). At present, no reaction was observed by the application of tension.

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