Effect of sucrose, auxins and gibberellic acid on rooting of stem segments of Populus nigra under varying light conditions

Abstract

This paper deals with the effects of sucrose, IAA, IBA and GA₃ on rooting stem segments of Populus in a sterile culture when exposed to varying periods of continuous dark. The results demonstrate that segments shorter than 3.5 cm in length, root only when exposed to 3 or more days of darkness, the number of roots increasing with the number of days in dark. The dark requirement for rooting can be substituted both by IAA and IBA, as rooting occurred with auxins even under continuous light. The failure of control segments to root under continuous light is ascribed to low auxin content due either to inadequate synthesis or its inactivation by light. This deficiency can be met either by exogenous application of auxins or by increasing the size of the segments. GA₃ inhibits rooting under favourable light conditions although it stimulates sprouting of buds and subsequent elongation. Sucrose increases the effectiveness of auxins.