The research in this book covers papers on a great number of research projects on the responses of plants and crops of natural terrestrial ecosystems, of agro-ecosystems, and of aquatic ecosystems, to enhanced solar UV-B as a result of stratospheric ozone depletion. Some introductory chapters deal with general aspects of how plants respond to UV-B radiation. Photosynthetically Active Radiation (PAR) is a primary energy resource for terrestrial plants, necessary for plant growth. Inevitably terrestrial plants absorb UV-B when exposed to solar radiation. The spectral balance between PAR and UV-B is discussed in several chapters. The responses of plants and ecosystems from the Antarctic and Arctic to