†This manuscript was submitted for publication in the Symposium-in-Print, and some of the material was presented as part of an invited talk for the ASP Symposium on UV Effects on Terrestrial Ecosystems presented in Seattle, WA, in July 2004.
Comparative Photobiology of Growth Responses to Two UV-B Wavebands and UV-C in Dim-red-light- and White-light-grown Cucumber (Cucumis sativus) Seedlings: Physiological Evidence for Photoreactivation†
Article first published online: 30 APR 2007
Photochemistry and Photobiology
Volume 81, Issue 5, pages 1069–1074, September 2005
How to Cite
Shinkle, J. R., Derickson, D. L. and Barnes, P. W. (2005), Comparative Photobiology of Growth Responses to Two UV-B Wavebands and UV-C in Dim-red-light- and White-light-grown Cucumber (Cucumis sativus) Seedlings: Physiological Evidence for Photoreactivation. Photochemistry and Photobiology, 81: 1069–1074. doi: 10.1562/2005-01-10-RA-411
- Issue published online: 30 APR 2007
- Article first published online: 30 APR 2007
- Received 10 January 2005; accepted 19 May 2005; published online 16 June 2005
We examined the influence of short-term exposures of different UV wavebands on the elongation and phototropic curvature of hypocotyls of cucumbers (Cucumis sativus L.) grown in white light (WL) and dim red light (DRL). We evaluated (1) whether different wavebands within the ultraviolet B (UV-B) region elicit different responses; (2) the hypocotyl elongation response elicited by ultraviolet C (UV-C); (3) whether irradiation with blue light–enriched white light (B/WL) given simultaneous with UV-B treatments reversed the effect of UV in a manner indicative of photoreactivation; and (4) whether responses in WL-grown plants were similar to those grown in DRL. Responses to brief (1–100 min) irradiations with three different UV wavebands all induced inhibition of elongation measured after 24 h. When WL-grown seedlings were irradiated with light containing proportionally greater short wavelength UV-B (37% of UV-B between 280 and 300 nm), inhibition of hypocotyl elongation was induced at a threshold of 0.5 kJ m−2, whereas exposure to UV-B including only wavelengths longer than 290 nm (and only 8% of UV-B between 290 and 300 nm) induced inhibition of hypocotyl elongation at a threshold of 1.6 kJ m−2. The UV-C treatment induced reduction in elongation at a threshold of <0.01 kJ m−2 for DRL-grown plants and <0.03 kJ m−2 for WL-grown plants. B/WL caused 50% reversal of the short-wavelength UV-B–induced inhibition of elongation in DRL-grown seedlings but did not reverse the effect of long-wavelength UV-B. B/WL caused 30% reversal of the UV-C–induced inhibition of elongation in WL-grown seedlings but did not affect the response to short-wavelength UV-B. Short-wavelength UV-B also induced positive phototropic curvature in both types of seedlings, and this was reversed 60% or completely in DRL-grown and WL-grown seedlings, respectively. The similarity of responses between the etiolated (DRL-grown) and de-etiolated (WL-grown) seedlings indicates that the short-wavelength specific response may be relevant to natural light environments, and the apparent photoreactivation implicates DNA damage as the sensory mechanism for the response.