SEEDS

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Seeds.

A seed is a developed fertilized ovule

A seed is a mature fertilized ovule

Groups of seeds

Monocotyledonous seeds

Dicotyledonous seeds

Monocotyledonous seeds

Monocotyledonous seeds are seeds with only one cotyledon

These are also called cereals or grains

Examples of monocotyledonous seeds

  • Maize seed
  • Millet seed
  • Oat seed
  • Wheat seed
  • Rice seed
  • Sorghum seed
  • Barley seed

Structure of a maize seed.

maize structure

Functions if each part of a maize seed

Endosperm

Endosperm stores food for the plant

Plumule

Plumule develops into a shoot system

Cotyledon

Cotyledon absorbs food from endosperm and supplies to the embryo during germination

Radicle

Radicle develops into a root system

Embryo

This is made up of the plumule and radicle

Embryo develops into a new plant

Testa (seed coat)

Testa protects the inner parts of the seed

Style scar

Style scar is the part where the style was attacked

Stalk scar

Stalk scar attaches

Note

  • Plumule sheath protects the plumule
  • Radicle sheath protects the radicle
  • A maize is a fruit because it has two scar

Dicotyledonous seeds

Dicotyledonous seeds are seeds with two cotyledons

Examples of dicotyledonous seeds

  1. Coffee seeds
  2. Beans
  3. Soya bean seeds
  4. Groundnut
  5. Simsim
  6. Mango seed
  7. Orange seed
  8. Avocado
  9. Tomatoes
  10. Cowpeas.

Structure of a bean seed

Bean seed 1

Function of each part of a bean seed

Testa (seed coat)

Testa protects the inner parts of a bean seed

Cotyledon

Cotyledon provides food to the germinating embryo

GERMINATION IN PLANTS

  • Germination is the development of a seed embryo into a seedling under favourable conditions.
  • During germination, the Radicle grows into the root system to support the seedling firmly into the soil.
  • The radicle also grows root hairs to absorb water and mineral salts from soil.

Types of germination.

There are basically two types of germination

  • Epigeal germination
  • Hypogeal germination

Epigeal germination is a type of germination where the cotyledon comes out of the ground.

Epigeal germination is a common characteristic of dicotyledonous seeds eg. Beans, soy beans, groundnuts.

structure showing the different stages in Epigeal germination.

epigeal germination

Hypogeal germination:

This is a type of germination in which the cotyledon remains under the ground

This type of germination is a common characteristic of monocotyledonous seeds.

Examples include; maize, millet, rice, sorghum etc.

hypogeal germination

Conditions necessary for seed germination.

  • A seed will only germinate under favourable conditions such as, oxygen, water and warmth.

Seed viability is the ability of a seed to germinate under favourable conditions.

A viable seed should be;

  • Mature and dry
  • Whole without a hole  / wrinkles
  • Health and of a good variety