Seed Germination

Abstract

Seeds control the survival and reproductive capacity of plants and therefore occupy a critical position in the life history of higher plants. The successful establishment of the new plant both temporally and spatially, as well as the vigour of the young seedling, is largely determined by physiological and biochemical processes that occurred earlier, i.e. during seed development. At dispersal, the quiescent mature seed upon encountering favourable environmental conditions (that can include light of a given wavelength, sufficient water, optimal temperatures and adequate oxygen) commences germination. However, as will be discussed, under conditions that are not optimal for a transition from germination to seedling growth, seeds express genes that impose a transient ‘quiescence’ until those conditions become optimal. The agricultural and forest industries rely upon seeds that exhibit high germinability and vigorous, synchronous growth after germination; hence dormancy is generally considered an undesirable trait. Some of the problems unique to the forest industry in relation to the deep dormancy of conifer species will be discussed. Functional genomic approaches hold promise for elucidating genes and proteins that control seed dormancy and germination. The understanding of molecular and physiological mechanisms underlying seed dormancy, particularly of angiosperms, has been accelerated through the analysis of mutants that are disrupted in their development (including dormancy inception and maintenance) as a result of a deficiency in hormone biosynthesis or response. These and other biotechnological approaches for manipulating germination will be discussed.