Mutualism and Parasitism: Diversity in Function and Structure in the 'Arbuscular' (VA) Mycorrhizal Symbiosis. Calcium Ions as Intracellular Second Messengers in Higher Plants. The Effects of Ultra Violet-B Radiation on Plants: A Molecular Perspective. Rapid Long-Distance Signal Transmission in Higher Plants. Keeping in Touch: Responses of the Whole Plant to Deficits in Water and Nitrogen Supply.