Received for publication September 15, 1977. Conducted under Hatch project 411, University of Georgia College of Agriculture Experiment Stations, College Station, Athens.
Graduate Student, Assistant and Associate Professors, respectively. This is a portion of a dissertation submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree in Plant Science. Present address: Dept. of Plant and Soil Science, French Hall, University of Mass., Amherst, MA 01003.