4
Germination and Emergence
Calvin Chong
University of Guelph, Vineland Station, Ontario, Canada
Bernard B. Bible
University of Connecticut, Storrs, Connecticut
Hak-Yoon Ju
Nova Scotia Agricultural College, Truro, Nova Scotia, Canada
57I. INTRODUCTION
A seed (zygote) results from the fertilization or union of male and female gametes and is the reproductive
structure of a plant. Thus, the regeneration or multiplication of plants from seed is termed sexual. Plants
are also reproduced by asexual (vegetative) means from bulbs or pieces of stem, root, or other plant part
[1].
A seed is essentially an embryo or young plant in the quiescent or dormant stage. In this state, the
embryo has an extremely low metabolic rate. Most seeds can survive on their stored reserves for pro-
longed periods. The seed is the primary means by which a plant reproduces itself at a later time when con-
ditions are suitable.
During fertilization, the genes controlling plant characteristics regenerate and recombine in many
different ways, resulting in seeds that may or may not mimic their parents. Seeds resulting from self-pol-
lination may produce true-to-type specimens, whereas those resulting from cross-pollination usually do
not. Cross-pollinated seeds provide genetic diversity for breeding and selection of new cultivars (culti-
vated varieties) and are often sources of new or novel plant material.
Some seedling plants are commonly grown as rootstocks for budding or grafting of cultivar fruit
trees, nut trees, and woody landscape plants or to produce superior landscape specimens that are difficult
to propagate asexually or for which asexual methods of propagation are unknown [2]. Regeneration from
seed is the most economical way to grow large numbers of plants. Most forest species, vegetables, and
flowering and other cultivated plants are grown from seeds.
A few species of plants produce seeds without undergoing fertilization. This form of reproduction is
called apomixis and is characteristic of species such as Poa pratensis(Kentucky bluegrass), which rarely
or never produces true seed. A plant grown from an apomictic seed is genetically identical to its parent.
II. SEED MORPHOLOGY
There are two major classes of seed-bearing plants: angiosperms (flower-bearing), whose seeds are borne
in ovules enclosed within the ovary or fruit, and gymnosperms (cone-bearing), whose seeds are borne in
pairs at the base of scales of the cones. An example of a seed from each of these classes of seed-bearing
plants is illustrated in Figure 1A and B.