Cytokinin activity in oak (Quercus robur) with particular reference to transplanting

Abstract

AbstractCytokinin activity in sap collected under vacuum from field grown oaks (Quercus robur L.) was determined at monthly intervals throughout the year. A very low level in January was followed by an increase in February and March which reached its maximum 20–25 days before bud‐break. Levels decreased through April and May during leaf expansion, rising once more in June, 10–15 days before a second shoot growth flush. The levels then progressively decreased to reach a minimum in November and December.Cytokinin activity in roots, 24 h and one week after root‐tip removal did not differ significantly from that in intact control plants. Cytokinin activity in roots and shoots determined in relation to shoot growth flushes revealed no differences in the shoot while the activity in root extracts was lowered after a single flush of shoot growth.The effects of applying growth regulators at the time of transplanting were investigated by soaking entire transplants in hormone solution. Gibberellin promoted shoot growth at the expense of root growth, but root growth could be restored to normal levels by a simultaneous application of auxin. Cytokinin treatment increased leaf number, but resulted in small bushy plants.The seasonal changes in cytokinin activity are discussed with regard to successful transplanting.