UV-B radiation and the green tide-forming macroalga Ulva

Abstract

Introduction. For plants, sunlight not only provides a source of energy to drive primary production, but also information to guide photo-morphogenesis and reproduction (Kendrick and Kronenberg 1994). Also light in the 400-700 nm waveband range (photosynthetic active radiation, PAR) solar radiation reaching the earth’s surface contains a small fraction of ultraviolet-B radiation (UV-B; 280-320 nm), which is harmful to plants. UV-B quanta have high levels of energy and are effectively absorbed by important biological molecules, such as DNA, proteins, and lipids, which subsequently get destroyed. UV-B radiation directly alters the structure of DNA and indirectly damages nucleic acids (Mitchell and Karentz 1993). Proteins absorb UV-B because of their tryptophan, tyrosine, and phenylamine contents (Yu and Bjorn 1997) and UV-B radiation affects membranes by causing large reductions in the total lipid content (Kramer et al. 1991).