Seed Development in Podocarpus henkelii: an Ultrastructural and Biochemical Study

Abstract

Biochemical and fine-structural studies were undertaken on the embryo and female gametophyte of seeds of Podocarpus henkelii during the 24-week period of post-fertilization growth and development. Although the d. wt of the embryo and female gametophyte showed a steady increase during development, the levels of sugars, amino acids, proteins and lipids differed between seed parts and showed changes during the four sampling intervals. Only starch was seen to increase steadily throughout development. Lipid levels were high in the mature embryo and free amino acids showed a steady increase until the seeds were shed. At this stage seeds were fully hydrated, possessed abundant reserves and all organelles appeared fully functional. This was interpreted as part of the development strategy of neotonous (recalcitrant) seeds, namely, the maintenance of full metabolic competence for continued growth in the absence of development arrest which follows drying in orthodox seeds.