Present address : Dept. of Horticulture, College of Agr., Chonnam National Univ., Kwangju, Chonnam, Korea.
Professor and Head, Dept. of Horticulture.
Professor, Dept. of Plant Science.
Received for publication 11 Oct. 1988. A portion of a thesis submitted by G.C.C. as partial fulfillment of the requirements for the PhD at the Lincoln Univ. College. We appreciate the computer program supplied by David R. Causton (Dept. of Botany and Microbiology, University College of Wales, Aberystwyth), for curve fitting. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.