ROOT FORMATION OF BLACK COTTONWOOD CUTTINGS IN RELATION TO REGION OF PARENT SHOOT

Abstract

Shoots of one-year-old Populus trichocarpa Torr. and Gray were collected just after breaking of dormancy from a nursery at Lulu Island, B. C. The shoots were divided into four sections of equal length and placed in an atmosphere of 100% relative humidity at a constant temperature of 4 °C. After one month the quarters were sampled to determine the number and length of adventitious roots formed and the number of new shoots. Significant differences were found in the number and length of roots produced in different quarters of the shoot but not in the number of new shoots. There were also significant differences in root length between clones. The most numerous and longest roots occurred on the lowest quarter of the shoot and decreased acropetally. The data suggest the better performance of cuttings of P. trichocarpa from the lower portions of the shoot and the importance of vigor in individual clones.