The Physiology of Rooting Populus Cuttings

AbstractActivity of endogenous cytokinin of cuttings was investigated in relation to the process of rotting. The levels of cytokinin in hardwood cuttings of easy‐to‐root Populus × euramericana (Dode) Guinier and difficult‐to‐root Populus tremula L. were monitored at various stages of root formation. In cuttings of P. tremula was found a higher cytokinin activity than in P. × euramericana and this condition persisted throughout the rooting period. There was a general initial decrease of cytokinin activity in both upper and lower halves of cuttings of both species. The declining level was reversed in the easy‐to‐root species when roots had formed and to a lesser extent in the difficult‐to‐root species when leaves expanded. In both cases this increase was relatively higher in the lower halves than in the upper halves.