Plant Physiologist, ARS, Rm. 206, B-001. BARC-W. and Chairman, ASHS Working Group on Developmental and Environmental Stress Physiology. Grateful acknowledgments are extended to the Cooperative State Research Service, USDA, Washington, D.C. for providing funds toward publication costs of this Symposium, and to Crop Genetics International N.V.. Dorsey. Md., for their contribution.