Involvement of phytochrome in stomatal movement: Effect of blue and red light

Blue and red light induce stomatal opening in Commelina comrnunis L. 3‐(3, 4‐di‐chlorophenyl)‐l, l‐dimethylurea (DCMU) slightly inhibits stomatal opening in blue light, while being strongly inhibitory in the presence of red light. Similar inhibition of red‐light‐induced opening is obtained by far red. Far red added to red light causes closure of open stomata almost to the degree obtained in darkness. Parallel to its effect on stomatal movement, far red increases ⁸⁶Rb leakage from guard cells. The antagonism of red and far red possibly indicates the involvement of phytochrome. It is proposed that chlorophyll fluorescence in the far red region, increased by DCMU, is responsible for the inhibitory effect of red light. Similarly, the stimulatory effect of blue light may be due to its fluorescence in the red region.