Abstract
The phytochrome system is analyzed in light-grown maize (Zea mays L.) plants, which were prevented from greening by application of the herbicide SAN 9789. The dark kinetics of phytochrome are not different in the first, second or third leaf. It is concluded that in light-grown maize plants phytochrome levels are regulated by Pr formation and Pfr and Pr destruction, rather than by Pfr→Pr dark reversion. Pr undergoes destruction after it has been cycled through Pfr. The consequences of this Pr destruction on the phytochrome system are discussed.