Red and far red effects on phenylalanine ammonia-lyase in raphanus and sinapis seedlings do not correlate with phytochrome spectrophotometry.

In seedlings of Raphanus sativus (radish) and Sinapis alba (mustard), irradiation for 6 hours with far red light significantly increases the extractable activity of phenylalanine ammonia-lyase by the end of the light period. A schedule of 10 minutes red light-110 minutes darkness-10 minutes red-110 minutes darkness-10 minutes red-110 minutes darkness has no effect as compared to dark controls. However, the red light program maintains a level of far red-absorbing phytochrome always measurable by in vivo spectrophotometry during the 6-hour experimental period. We conclude that the far red effect on this enzyme and for this specific material cannot be explained solely by formation and maintenance of far red-absorbing phytochrome.