Evidence of Phytochrome Mediation in the Low-pH-Induced Root Hair Formation Process in Lettuce (Lactuca sativa L. cv. Grand Rapids) Seedlings

−2 . The inductive effect of 100 Jm⁻² red light could be partially reversed by subsequent far-red light only one time. On the other hand, the inductive effect of 1,000 Jm⁻² red light was partially reversed by subsequent far-red light irradiation at least twice. These results indicate the involvement of phytochrome in this response. The inductive effect of blue light was repeatedly reversed by subsequent far-red light irradiation, suggesting that the blue-light induction was mainly mediated by phytochrome. Received 13 August 1999/ Accepted in revised form 22 December 1999