The aim of this monograph is to highlight various mechanisms followed by plants to overcome the high light stress and photoinhibition, and also the plant responses to low light levels. Emphasis has been on the regulation of light harvesting process, the avoidance phenomena at leaf and chloroplast levels and the strategy followed by certa in solar tracking plants in maximizing the light interception without photoinhibitory damage, leading to improvement of diurnal photosynthetic rate. Plant adjustment to light variations over a long term, through the acclimation process brought about by changes in gene function and specific reconstruction of chloroplast has also been discussed. Although the emphasis has been on higher plant systems, green algae and cyanobacterial examples are used wherever appropriate. This book will be a useful reference to advanced postgraduate students, research scientists and teachers interested in the area of photosynthesis research.