A Study of Chlorophyll in a White Mutant Strain of Helianthus annuus

Abstract

One of the seedlings of H. annuus treated by the senior author in 1948 to ultrasonic vibrations gave a yellow mutant in F2, and later, in F5 gave a second mutant which is pearl white. Both mutants breed perfectly, and the white one gives an almost perfect single recessive ratio when grown in the field. This study deals primarily with the white mutant. Extensive tests show this white strain to be devoid of carotinoids, but nevertheless it is a vigorous seedling, grafts freely, and as a scion sets seed to its own pollen. The seedling reacts to gravity and light, and under sutiable conditions produces one-half to two-thirds as much protochlorophyll, chlorophyll a and chlorophyll b, as do seedlings of its green sib under like conditions. The ratios of these three pigments is stable over a wide range of conditions. A wide range of studies on light intensities and exposure times show maximum pigment production within 72 hours at 0.5 fc of light. Exposures from 2 to 16 hours to light intensities of 250 to 2000 fc cause severe fading.