Phytochrome is not involved in the red‐light‐enhancement of the stomatal blue‐light‐response in wheat seedlings

The stomatal response to blue light (BL) in wheat seedlings (Triticum aestivum L. cv. Starke II, Weibull) was enhanced by background red light (R). This enhancement was only slightly affected by the addition of background far‐red light (FR). Under similar light treatments, the addition of FR induced a 43% transformation from the far‐red‐absorbing form towards the red‐absorbing form of phytochrome from etiolated oat (Avena sativa L. cv. Sol II), immobilized on phenyl‐sepharose. Furthermore, the enhancement of the stomatal BL‐response by 15 min R was not reversed by a subsequent irradiation with 5 min FR. It is concluded that the red‐light‐enhancement of the stomatal blue‐light‐response in wheat seedlings does not involve a change in the photostationary state of phytochrome.