SOME FACTORS IN THE DEVELOPMENT OF CALLUS IN POPLAR CUTTINGS

The effect of temperature, moisture content of the cutting, and location within the shoot and cutting on callus production were investigated in Populus trichocarpa Torr. and Gray, P. canadensis Moench 'Regenerata', and P. canadensis 'Robusta Bachelieri'. Callus production increased with temperature and moisture content although not to the same extent in the three varieties. Cuttings from the base of the shoot produced more callus than those from the upper part. The latter cuttings produced more callus from the end which had been lowermost in the parent shoot than that which had been uppermost. However, cuttings from the base of the shoot showed this difference between ends of cuttings only in P. 'Regenerata'.