Previous studies on the genetics of chlorophyll production have revealed the involvement of a gene Y11 , which is incompletely dominant. Thus, three phenotypes may be observed -- plants with leaves that are normally pigmented, light-green or yellow. The yellow is a lethal in nature; however, we have propagated them under laboratory conditions either by grafting the yellows to wild-type plants or growing them independently under constant low-level illumination with a short period of moderate (400 ft-c) illumination each day.