Types of Germination of Seed

Types of Germination of Seed

3 IMPORTANT TYPES OF GERMINATION

  1. HYPOGEAL GERMINATION
  2. EPIGEAL GERMINATION
  3. VIVIPAROUS GERMINATION

Both the epicotyl and hypocotyl of a seed never elongate together during germination. It is either the epicotyl or the hypocotyl that elongates. 

HYPOGEAL GERMINATION

  • If the epicotyl of the seed elongates and the cotyledons remain underground the germination is  called hypogeal .
  • Cotyledons remain inside the soil in Hypogeal Germination . 
  • Hypocotyl is short and its upper part of the hypocotyl is not curved down. 
  • Epicotyl is long in Hypogeal Germination.  
  • Cotyledons do not undergo Photosynthesis in Hypogeal Germination .
  • In Hypogeal germination energy comes from the endosperm. Example coconut, pea and maize

EPIGEAL GERMINATION

  • If the Hypocotyl elongates, the cotyledons are pushed above the ground this type of germination is called Epigeal Germination.
  • Hypocotyl is long and its upper part of the hypocotyl is curved down to protect the plumule. Epicotyl is short Cotyledons turn green and undergo photosynthesis 
  • Energy comes from Cotyledons in Epigeal Germination . 
  • Epigeal Germination usually occurs in dicotyledonous seeds.Example beans and castor.

Also Check – 9 Key Differences Between Radicle and Plumule

Examples  to Study Different types of Seed Germination

To study different types  of seed germination. Put sterilized sand in a glass vessel in which filter paper or ordinary white paper is lined beside the inner wall, and place seeds in between the paper and the glass. When water is added to the sand in the vessel, seeds  will absorb the water and germinate in a few days.

Epigeal Germination- Bean Seed

To Study Different types of Seed Germination
Epigeal Germination – Bean
  • The Bean seed absorbs water and swells. 
  • The radicle grows downwards to form the root system. 
  • The arched hypocotyl grows forming an arch/loop above the soil, it then straightens bringing the cotyledons above the soil. 
  • Germination in Bean Seed is, therefore, Epigeal (epi: above; geo: earth). 
  • The cotyledons become the first green leaves and soon fall off after the foliage leaves grow.

Hypogeal Germination – Pea Seed

To Study Different types of Seed Germination
Hypogeal – Pea Seed Germination
  • The pea seed absorbs water and swells considerably. 
  • The testa softens and bursts. 
  • The radicle emerges, grows downwards and forms the root system. 
  • The plumule grows upwards and forms the shoot of the seedling. 
  • In the earlier stages of development, the plumule is arched and thus protects the young shoot from injury during its emergence from the soil. 
  • The cotyledons supply food till the seedling is able to exist independently. 
  • Later they wither and shrivel up. 
  • The cotyledons remain underground and germination is hypogeal (hypo- below + geo- earth).

Hypogeal Germination – Maize Grain 

To Study Different types of Seed Germination
Hypogeal – Maize Grain Germination
  • The grain imbibes water and swells considerably. 
  • The radicle pierces through the protective root sheath (coleorhiza) and the fruit wall and grows
  • downwards to form the root system, but it dies off soon.
  •  New roots develop from the base of the stem (adventitious roots).
  • The plumule pierces through its protective sheath, coleoptile, and grows straight upwards. 
  • The two protective sheaths, coleorhiza and coleoptile, may be seen as a membranous covering on the axis of the seedling.
  • The cotyledon (scutellum) absorbs food from the endosperm till it is exhausted. 
  • The Hypocotyl does not elongate. Germination is Hypogeal.

Viviparous germination – Mangrove plant

To Study Different types of Seed Germination
Viviparous germination – Mangrove plant
  • Mangrove Plants like Rhizophora and Sonneratia, show a special mode of seed germination called vivipary in which seed germinates inside the fruit while it is still attached to the parent plant. 
  • After germination, the plant drops the seedling into the soil which develops a root and fixes itself. (Viviparous producing live young ones)

Also Check – 8 Important Differences between Epigeal and Hypogeal Germination

Also Check – What is Germination

Also Check- What is Seedling ?

Also Check – Structure of the Seed

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