Theory:

The process of development of a new plant from the seed is known as germination.
Sunflower_growing_time_lapse.gif
Germination of seed
 
It is a slow biological process. Hence, the seeds in a dry state are alive, but remain dormant.
 
Conditions necessary for germination:
  • Water
  • Air (oxygen)
  • Favourable temperature
Role of water in seed germination:
  • It helps in softening by of the seed by rupturing the seed coat.
  • Allows the plumule and radicle to emerge out of the seed coat.
  • Converts the stored food into soluble material.
  • Transports the soluble food from the storage tissue to the embryo.
  
Role of oxygen in seed germination:
  • It provides energy required for the process of germination.
  • It facilitates aerobic respiration to liberate energy.
  • Increases the rate of respiration.
  • Oxidation of food takes place with the help of oxygen.
Role of temperature in seed germination:
  • As different biological processes takes place during the process of respiration an optimum temperature is required.
  • Hence, maintenance of an optimum temperature ranging from \(25 to 35°C\) is required,
Types of germination:
Germination of seeds occurs in two ways:
  • Hypogeal
  • Epigeal
800px-Germination-en.svg.png
Different types of germination
 
Hypogeal germination in seed:
 
In the term hypogeal 'hypo' refers to below and 'geo' refers to earth.
 
shutterstock_1342092032.png
Epigeal germination
  • During this type of germination the seeds swell due to the absorption of water leading to the bursting of testa.
  • The radicle emerges and grows downwards and forms the root.
  • The plumule grows upwards and forms the shoot.
Epigeal germination of the seed:
  
In the term epigeal 'epi' refers to above and 'geo' means earth.
 
shutterstock_1340921324.png
Hypogeal germination
  • During this type of germination the seeds swell due to the absorption of water.
  • The radicle emerges and grows downwards and forms the root.
  • Hypocotyl forms an arch and grows above  the soil, and brings the cotyledons above the soil.
Reference:
https://upload.wikimedia.org/wikipedia/commons/c/c7/Sunflower_growing_time_lapse.gifhttps://commons.wikimedia.org/wiki/File:Germination-en.svg