THE ONTOGENY OF ADVENTITIOUS STEMS ON ROOTS OF CREEPING-ROOTED ALFALFA

Abstract

An ontogenetic study of adventitious stem formation on root segments of creeping-rooted alfalfa clones is presented. Unusual meristematic activity is evident first in the phellogen near a lateral rootlet. Continued activity in that region gives rise to a primordial dome from which adventitious stems eventually emerge. Concomitantly, in the subjacent phloem parenchyma cells dedifferentiation and subsequent redifferentiation into vascular tissues occurs. Thus a vascular system is formed which extends from the adventitious stems to the cambium region of the root and, in some instances, to the cambium of the lateral rootlet. Adventitious stems are initiated in secondary tissues of the root. Factors such as age of root, culture treatment, and inherent differences have an influence on adventitious stem initiation.