The ultrastructural, histochemical, and biochemical development of the post-fertilization megagametophyte and the zygotic embryo of Pseudotsugamenziesii

Abstract

Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) megagametophyte and embryo development were studied from fertilization until seed maturity, a period of about 71 days. The most important morphogenetic events occurred during the first 43 days. During this time lipid bodies and protein bodies increased rapidly in the megagametophyte. Lipids, proteins, and starch became evident in the embryo toward the end of the morphogenetic phase. The subsequent embryo maturation phase showed slight increases in size and number of megagametophyte lipid bodies and protein bodies, as well as an increase in protein body complexity. Later, in the mature seed, lipids and proteins were distributed uniformly in the megagametophyte. Starch was abundant in some regions of the embryo but not abundant in the megagametophyte. In mature seeds soluble sugars made up 2 and 3%, proteins 16 and 11%, and lipids 60 and 45% of the megagametophyte and embryo dry weight, respectively. Histochemical and ultrastructural observations confirmed these amounts of lipids and proteins and showed their distribution in megagametophytes and embryos during development.