title: Action of Phytochrome During Prechilling of Amaranthus retroflexus L. Seeds.
abstract: Dark germination of Amaranthus retroflexus L. seeds at 35 degrees increased after several days of prechilling at 20 degrees or lower. Irradiation with far-red light for short periods during the early hours of a prechilling period at 10 degrees inhibited subsequent dark germination at 35 degrees . The inhibition was completely reversible with red light. Far-red irradiation in the latter part of the prechilling period was less effective. Increased dark germination of A. retroflexus seeds following a prechilling period at 20 degrees or less is attributed to action of preexistent P(FR), the far-red absorbing form of phytochrome, within the seeds. Inactivation of P(FR) was found to proceed ca. 4 times more rapidly at 25 degrees than at 20 degrees . Failure of imbibition temperatures above 20 degrees to increase dark germination of A. retroflexus seeds is attributed to the rapid thermal reversion of pre-existent P(FR). We suggest that the action of prechilling (layering) on many other seed kinds arises in a similar way.
authors.affiliation: Crops Research Division, United States Department of Agriculture, Beltsville, Maryland 20705.
authors.forename: R B
authors.initials: RB
authors.lastname: Taylorson
authors.forename: S B
authors.initials: SB
authors.lastname: Hendricks