a1 USDA – ARS, Room 218, Building 004, BARC – West, Beltsville, MD 20705, USA
Amaranthus albus L. seeds able to germinate in darkness can be prevented from germinating by prolonged irradiation with incandescent light (CIL). The germination in darkness is controlled by pre-existent Pfr. Allowing the seeds to remain in darkness for about 16 h allows an escape from the inhibition by CIL, about comparable with the time required to escape from pre-existent Pfr control. By examining escape from low fluence far-red (FR), it was found that no escape occurred in CIL. It was concluded that the mode of action of CIL in inhibiting A. albus seed germination involved prevention of the action of the pre-existent Pfr and a subsequent dormancy which does not allow a response to the Pfr generated by the incandescent light. Other actions of CIL were found but were considered less likely as causative for the inhibition of germination. One was a direct inhibition of radicle elongation and another involved prevention of an increased responsiveness to Pfr induced by treatment at 40°C.
(Received August 10 1990)
(Accepted November 01 1990)
c1 Correspondence to current address: Department of Plant Science, University of Rhode Island, Kingston, RI 02881, USA