2 - Seed Germination and Seedling Growth

Abstract

This chapter discusses the seed germination and seedling growth of woody plants. The greatest risk of mortality of woody plants is during the ungerminated embryo stage of seed development and in the cotyledon stage of seedling development. The essential structure in a seed is the embryo, and growth and development of the embryo into a new independent seedling involves respiration, absorption of water, conversion of foods into soluble forms, synthesis of enzymes and hormones, and nitrogen and phosphorus metabolism. Seed germination can be considered to be the resumption of embryo growth resulting in a seed coat rupture and emergence of the young plant. The growth of an embryo requires both cell division and elongation; in some species cell division may occur first while in others cell elongation may occur first. The most important environmental factors controlling seed germination are water, temperature, light, oxygen, and various chemicals. The cotyledons play a major role in seedling growth and development in both gymnosperm and angiosperm seedlings, as cotyledons are important in storage of foods and mineral nutrients, in photosynthesis, and in the transfer of the growing axis of substances needed for growth.