ELECTRIC-FIELDS AFFECT THE ORIENTATION OF CORTICAL MICROTUBULES AND CELL EXPANSION IN PEA CALLUS

Cortical microtubules in callus derived from Pisum sari vum roots form parallel arrays within cells but are randomly oriented across the tis sue. These arrays align perpendicular to the direction of an applied e lectric field of 6 mV per cell. Application of a field of 6 mV per cel l for 4 days resulted in the co-ordinated expansion of cells parallel to the field direction. Cortical microtubule arrays were still aligned perpendicular to the applied field 24 h after removal of the field. T he imposition of a field to callus after the removal of cortical micro tubules by oryzalin and in the presence of the herbicide resulted in t he orientation of recovering microtubules perpendicular to the directi on of the field, indicating that microtubules are not directly involve d in the detection of the field.