The current climatic changes mean increasing environmental stress on plants. Gaseous pollutants, such as carbon dioxide, sulphur dioxide, ozone and oxide of nitrogen, combine with the impacts of flooding and submergence, drought and cold. This book examines the physiological, biochemical and molecular biological bases of injury and adaptations to stress in plants. Emphasized is the importance of the combined effect of more than one type of stress, for example increased ultraviolet (UVB) radiation exacerbating injury from drought or offsetting the beneficial effects of an increase in atmospheric carbon dioxide. The prospects for improving tolerance to environmental stress by genetic engineering are assessed and some examples of recent progress are described.