Abstract
Dark germination of Amaranthus retroflexus L. seeds at 35° increased after several days of prechilling at 20° or lower. Irradiation with far-red light for short periods during the early hours of a prechilling period at 10° inhibited subsequent dark germination at 35°. 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° or less is attributed to action of preexistent PFR, the far-red absorbing form of phytochrome, within the seeds. Inactivation of PFR was found to proceed ca. 4 times more rapidly at 25° than at 20°. Failure of imbibition temperatures above 20° to increase dark germination of A. retroflexus seeds is attributed to the rapid thermal reversion of pre-existent PFR. We suggest that the action of prechilling (layering) on many other seed kinds arises in a similar way.
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Selected References
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