9. SEED GERMINATION
•Germination is the process by which
an organism grows from a seed or similar
structure.
•The most common example of germination is
the sprouting of a seedling from a seed of
an angiosperm or gymnosperm.
• In addition, the growth of a sporeling from
a spore, such as the spores
of hyphae from fungal spores, is also
germination.
10. • The part of the plant that first emerges from the seed is the embryonic
root, termed the radicle or primary root.
• It allows the seedling to become anchored in the ground and start
absorbing water.
• After the root absorbs water, an embryonic shoot emerges from the
seed.
• This shoot comprises three main parts: the cotyledons (seed leaves), the
section of shoot below the cotyledons (hypocotyl), and the section of
shoot above the cotyledons (epicotyl).
• The way the shoot emerges differs among plant groups.
12. Seed germination : Mechanisms
• Seed germination represents a dynamic period in life cycle of plants as a seed
makes the transition from a metabolically quiescent to an active and growing
entity.
• The sequence of germination in its simplest form:
1. Water imbibition
2. Enzyme activation
3. Hydrolysis and catabolism of storage materials
4. Initiation of growth
5. Formation of new cells
6. Rupture of seed coat and
7. Emergence of seedling
16. a. Epigeal germination
• In epigeal germination (or
epigeous germination),
the hypocotyl elongates and
forms a hook, pulling rather
than pushing
the cotyledons and apical
meristem through the soil.
• Once it reaches the surface, it
straightens and pulls the
cotyledons and shoot tip of the
growing seedlings into the air.
• Beans, most of the vegetables,
tamarind and papaya are
examples of plants that
germinate this way.
17. b. Hypogeal
• In this type of germination, the epicotyl elongates and forms the
hook.
• In this type of germination, the cotyledons stay underground
where they eventually decompose.
• Peas, gram, groundnut and mango, for example, germinate this
way.
18. 2.Monocot germination
• In monocot seeds, the embryo's radicle and cotyledon are covered
by a coleorhiza and coleoptile, respectively.
• The coleorhiza is the first part to grow out of the seed, followed
by the radicle.
• The coleoptile is then pushed up through the ground until it
reaches the surface.
• There, it stops elongating and the first leaves emerge.
