Question

Explain the germination of seed and type of germination with the help of a suitable diagram. What are the conditions necessary for germination?

Answer 1

Germination:

1. The beginning of growth of the seed into a new plant is called germination.
2. Germination begins when the seed absorbs water, wells and bursts through the seed coat.
3. The embryo formed is later differentiated into plumule (shoot part), radicle (root part) and cotyledons.
4. Shoot portion between cotyledon and plumule is known as epicotyl.
5. Root portion between cotyledon and the radicle is termed as hypocotyl.

Types of germination:

1. Epigeal germination
2. Hypogeal germination

Epigeal germination:

1. In epigeal germination, the hypocotyl moves rapidly upward pulling the cotyledons which move above the soil.
2. It is mainly observed in the dicotyledonous seeds.
3. Examples: Bean, coconut, Papaya, gourd, castor etc.

Hypogeal germination:

1. In hypocotyl germination, the epicotyl elongates and cotyledon remain below the soil.
2. It is observed in the monocotyledons seeds.
3. Examples: Pea, mango, maize, rice and groundnut etc.

Conditions necessary for germination:

1. Oxygen:
   • Rapid cell division takes place in the seed germination and energy is required.
   • Oxidation is done for the production and energy.
   • By the air, oxygen is supplied which facilitates the oxidation.
2. Temperature:
   • Optimum temperature is required for the germination of the seed.
   • Low temperature retards the embryonic activities whereas high temperature destroys the delicate embryo tissues.
3. Water:

• Moisture aids by providing hydration for protoplasm's critical activities.
• Water provides dissolved oxygen for the developing embryo.
• It softens the seed coating, and increases seed permeability.