An increased supply of food is urgently needed to provide adequate nutrients to the increasing world population. Plant foods are basic in the nutrition of man. Increasing the productivity and efficiency of plant foods is, therefore, essential. Application of low concentrations of certain chemicals have helped in making a breakthrough in this direction. Certain chemicals are known to stimulate plant growth and yield. Many growth regulators also increase the protein content of plants. Treatment with pesticides and herbicides may also change the nutritive quality. These effects have been explored in detail for specific food crops and individual chemicals and the findings are presented here. It should be noted, however, that most of these findings are of an experimental nature and their practical application will depend upon the discovery of more powerful chemicals and further research into less expensive ways to use them with fewer side effects.