SUCROSE REQUIREMENTS AND LIPID UTILIZATION DURING GERMINATION OF INTERIOR SPRUCE (PICEA-GLAUCA ENGELMANNII COMPLEX) SOMATIC EMBRYOS

Both somatic and excised zygotic embryos of interior spruce (Picea gla uca engelmannii complex) required exogenous sucrose in the medium for germination in vitro. Over a period of 29 days on sucrose-containing m edium germinants with roots and epicotyls developed from both kinds of embryo, and their content of linolenic acid (9,12,15-18:3) increased about six- to eightfold. Without added sucrose, embryos showed retarde d growth or were necrotic, and the content of linolenic acid was barel y detectable in their fatty acid profiles. Through C-14-sucrose uptake studies, it was determined that germinants consumed only 25% of the s ucrose available in a 1% (wt/vol) sucrose-containing medium. Since no radiolabelled fatty acids were detected, it appears that externally su pplied sucrose was not used in the synthesis of lipids. Although sucro se was present during plantlet development, 72% of the initial lipids were consumed. To some extent, the plantlets appeared to be obligate s torage lipid utilizers.