Growth and bract pigmentation in poinsettia as influenced by fast neutron irradiation

A study was made on growth and bract pigmentation in poinsettias Influenced by fast neutron Irradiation. Plants from two varieties of poinsettia, Mikkelpink, a periclinal chimera, and Spring Pink, agenetic pink, were irradiated with 300 rads of fast neutrons. Successive generations of cuttings were rooted from these plants and allowed to flower. At this time bract diameter and plant height were measured for growth responses. Color changes on bracts were also recorded according to size, type and frequency. It was found that plant height and bract diameter were reduced by irradiation only when the shoots from which cuttings were made were present at the time of irradiation. Most of the changes in bract color were found on Mikkelpink, the periclinal chimera. Changes from pink to red or white occurred at about the same frequency, these sectors became fewer and larger as successive crops of cuttings were removed from the mother plants.