Abstract
The stomata of the fern Adiantum capillus-veneris lack a blue light-specific opening response but open in response to red light. We investigated this light response of Adiantum stomata and found that the light wavelength dependence of stomatal opening matched that of photosynthesis. The simultaneous application of red (2 micromol m(-2) s(-1)) and far-red (50 micromol m(-2) s(-1)) light synergistically induced stomatal opening, but application of only one of these wavelengths was ineffective. Adiantum stomata did not respond to CO2 in the dark; the stomata neither opened under a low intercellular CO2 concentration nor closed under high intercellular CO2 concentration. Stomata in Arabidopsis (Arabidopsis thaliana), which were used as a control, showed clear sensitivity to CO2. In Adiantum, stomatal conductance showed much higher light sensitivity when the light was applied to the lower leaf surface, where stomata exist, than when it was applied to the upper surface. This suggests that guard cells likely sensed the light required for stomatal opening. In the epidermal fragments, red light induced both stomatal opening and K+ accumulation in guard cells, and both of these responses were inhibited by a photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The stomatal opening was completely inhibited by CsCl, a K+ channel blocker. In intact fern leaves, red light-induced stomatal opening was also suppressed by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. These results indicate that Adiantum stomata lack sensitivity to CO2 in the dark and that stomatal opening is driven by photosynthetic electron transport in guard cell chloroplasts, probably via K+ uptake.
Highlights
The stomata of the fern Adiantum capillus-veneris lack a blue light-specific opening response but open in response to red light
We demonstrated that the guard cells are insensitive to CO2 and that the guard cell chloroplasts are responsible for stomatal opening in response to light in this plant species
The application of photosynthetically saturating red light at 600 mmol m22 s21 induced a fast increase in stomatal conductance (Fig. 1A; Doi et al, 2006)
Summary
Stomatal responses to light were investigated in intact Adiantum leaves using gas exchange techniques (Fig. 1). The application of photosynthetically saturating red light at 600 mmol m22 s21 induced a fast increase in stomatal conductance (Fig. 1A; Doi et al, 2006). The initial rates of conductance increase by red and blue light were 0.061 6 0.011 and 0.063 6 0.009 (means of five measurements 6 SE) mmol m22 s22, respectively. To characterize the mechanisms underlying the stomatal responses to light in Adiantum, we determined the light dependence of the conductance increase using red, green, and blue light (Fig. 1B). The slopes of the linear regression lines in blue, green, and red light were 0.043 6 0.003, 0.042 6 0.003, and 0.048 6 0.006 (average of three measurements 6 SE), respectively. The lines were parallel to each other Using these data, we determined the effectiveness of each light wavelength (Table I). A chimeric protein of phototropin and phytochrome, did not function as a photoreceptor for red light-induced stomatal opening in
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
