The Initiation and Development of Lateral Meristems in the Pea Root

Abstract

The effect of distinct regions of the root on the initiation of lateral root pri mordia and the emergence of lateral roots has been studied, using segments of roots from sterile 2-day germinated pea seedlings. It is shown that the removal of the basal region causes a decrease in the number of primordia formed in the remainder of the root. On the other hand, the removal of the apical region causes a larger number of primordia to be formed in the remaining tissue than in the corresponding tissue of roots where the apical region is retained. It is suggested that a factor or a complex of factors involved in pri mordium initiation is translocated from the older tissue towards the potential site of primordium initiation in the young tissue which has just completed extension growth. The removal of the apical region of the root is also shown to stimulate lateral root emergence. It is suggested that a factor or complex of factors involved in the development of the primordia subsequent to initiation moves within the root in a similar manner to the factor or factors involved in initiation.