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The ultraviolet action spectrum for stomatal opening in broad bean
W Eisinger1, T E Swartz, R A Bogomolni
1Biology Department, Santa Clara University, Santa Clara, California 95053, USA.
Plant Physiology
|January 13, 2000
Summary
Ultraviolet light triggers stomatal opening in broad bean leaves, acting through the blue light photoreceptor. This UV response, peaking at 280 nm, suggests a flavin or carotenoid chromophore is involved.
Area of Science:
- Plant physiology
- Photobiology
- Spectroscopy
Background:
- Stomatal opening is crucial for plant gas exchange and is regulated by light.
- Previous studies focused on blue and red light, leaving the role of ultraviolet (UV) light less understood.
Purpose of the Study:
- To determine the ultraviolet action spectrum for stomatal opening in broad bean (Vicia faba).
- To investigate the photoreceptor involved in UV-induced stomatal opening and its relationship with blue light responses.
Main Methods:
- Measurement of stomatal opening using epidermal peels of Vicia faba.
- Calculation of the UV action spectrum using 11 wavelengths (275–459 nm) and hyperbolic fluence response curves.
- Light-mixing experiments involving UV, blue, and red light to probe photoreceptor interactions.
Main Results:
- A major peak in the UV action spectrum for stomatal opening was observed around 280 nm, with a minor peak near 360 nm.
- UV light saturated stomatal opening at very low fluence rates, significantly lower than blue light.
- UV light addition to saturating red light caused further stomatal opening, but addition to saturating blue light did not, indicating UV acts via the blue light pathway.
Conclusions:
- Ultraviolet light induces stomatal opening in Vicia faba, primarily through the blue light photoreceptor, not photosynthesis.
- The action spectrum suggests a flavin or cis-carotenoid chromophore is responsible for UV absorption.
- UV light may directly excite the chromophore or transfer energy after absorption by the protein component.