Root Regeneration and Root Dormancy in Taxus spp.1

Abstract

Abstract The annual cycle of root-regeneration potential (RRP) of 3 year old Taxus hunnewelliana Rehd., plants was evaluated by recording the number of new root initials produced 6 weeks after bare root transplanting. During the summer (June, July and August) few root initials were produced. The RRP increased throughout the fall (September to December) reaching a peak in January. This was followed by a drop in RRP through the spring and early summer (February to June). Root dormancy of 1 year old Taxus cuspidata Sieb. and Zucc., can be broken in February by an exposure to 7 weeks of chilling at 35°F. Shoot bud dormancy can be broken by an exposure to 3 weeks of chilling at 28°F. The chilling treatment breaking root dormancy appears to be sensed primarily by the root system. Chilling shoots only increased growth of dormant roots but does not substitute for the chilling requirement of the dormant root. The annual cycle of root-regeneration potential can be partially explained by root dormancy or root-shoot competition for photosynthate. The root-regeneration potential for transplanted Taxus hunnewelliana appears to be controlled by the same factors as the annual cycle of rooting for stem cuttings.