Environmental stresses represent the most limiting factors to agricultural productivity worldwide. Their impact is not only on presently cultivated crops, they are also significant barriers to the introduction of crop plants in noncultivated areas. A significant global problem in the improvement of agriculture is the major variation in annual crop yields due to variations in environmental stresses such as drought, flooding, salinity, and temperature variations. This summary presents current background and research knowledge on all important environmental stresses and their respective influence on plant growth, development and crop yield as well as on biochemical and physiological events within plant tissues in reaction to changing environmental conditions.