Abstract:Transmission of variation potential(VP)in willow(Salix babylonica)plantlet can be evoked by treating the root with 500 mmol/L NaCl solution，or by a local burn on the stem． VP transmission can still occur，if the rind is removed by ringing．But transmission fails if a portion of the central woody core(xylem)is removed furthermore，its transmission rate varies with the extent of water supply．The normal rate is kept in adequate water supply．And would slow down or come into standstill as water shortage is getting severe．The results seem to indicate that in the present case，Ricca′S factor released at the NaCl-treated root(serving as the chemical signal)can be carried along through xylem by transpiration stream．VP appears at the rind on its arrival．