Evidence for bound phytochrome in oat seedlings.

Phytochrome is consistently observed in pellets centrifuged from homogenates of etiolated, 5-day-old oat seedlings. The majority of pigment associated with the pellet cannot be removed by buffer washes, nor can appreciable quantities of additional phytochrome be adsorbed onto the sedimented material. Over 70% of phytochrome in the pellet is released by 1% Triton X-100.Storage at 0 degrees , irradiation by white light, and Triton treatment all cause much greater loss of photoreversibility in pelleted phytochrome than in supernatant phytochrome. We conclude that the phytochrome in the 1500 to 40,000g (30 min) pellet is distinct from the soluble phytochrome in the supernatant.