Horticulture Principles and Practices

Anther
Microspore
Megaspore mother cell
FIGURE 9–1 Reproduction in
flowering plants involves pollination
and fertilization.
Pollen grain
Mature ovary
Pollination
Sperms
Primary endosperm nucleus (3n)
Zygote (2n)
Fertilization
into the endosperm, a nutrient-rich mass of cells that provides nourishment to the embryo
until it develops to a stage where it becomes self-supporting (seedling stage).
The mature ovule is the seed. The outer tissue of the ovules (the inner and outer
integuments) fuse and lose their water to become the seed coat, or testa. The endosperm
contains large amounts of starch that serve as food reserves to be broken down into
glucose for use during seed germination. In monocots, the outermost layer of the
endosperm is called the aleurone layer and is the site of protein storage. In seeds such as
sunflower, mustard, pine, and fir, the endosperm stores a large amount of fats and oils.
The embryo is variable in size in terms of the volume of the seed it occupies.
It occupies a large volume in species such as pea and oak, but occupies a relatively small
volume in cereals. In species such as holly and orchid, the embryo remains relatively
undifferentiated. However, in grass, the embryo is highly differentiated into structures
including the shoot apex, scutellum (single cotyledon), and coleoptile (a cylindrical
protective leaf). The root apex is protected by the coleorrhiza.
Seed
The mature ovule of
a flowering plant.
9.2 SEED PRODUCTION AND CERTIFICATION PROCESS
Plant breeders are engaged in plant improvement. Old cultivars are changed by importing
new genes that condition improved characteristics, making new cultivars more disease
resistant, higher yielding, more beautiful, and better in other ways according to
breeding objectives. Once the breeder has completed the breeding program and tested
the new material extensively, the seed is then released by the researchers to special
producers for propagation.
Before the seed becomes available to the ordinary grower, it goes through stages
of increase and certification. According to the stages, there are four classes of seed
(Figure 9–2):
1. Breeder seed. A small amount of seed is developed and released by a breeder as
the source of foundation seed.
2. Foundation seed. Breeder seed is increased under supervision of agricultural
research stations and monitored for genetic purity and identity.
9.2 Seed Production and Certification Process 285