ABSTRACT
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). As well as 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; 280–315 nm), which is harmful to the biota. 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 phenylalanine contents (Yu and Bjorn 1997) and UV-B 203radiation affects membranes by causing large reductions in the total lipid content (Kramer et al. 1991).
