There are 3 different types of seed germination. (i) Epigeal, (ii) hypogeal, (iii) viviparous
(i) Epigeal germination
In this, the cotyledons are raised out of the soil and generally become green and photosynthetic. In dicots, they are pushed up by rapid extension of hypocotyl before growth of the epicotyl. Epigeal germination occurs in bean, caster, mustard, tamarind, sunflower etc.
(ii) Hypogeal germination
In this type of genmination, the cotyledons remain underground. Hypocotyl growth is restricted. The epicotyl grows to raise the first leaves out of the soil. Hypogeal germination occurs in dicotyledenous seeds of gram, pea, mango, ground nut etc and in monocotyledons like rice, maize, wheat etc.
(iii) Viviparous germination
This is a special type of germination occurring in mangrove plants. These plants generally grow in salty lakes, sea coasts and deltas. Here, the seed genminates while still attached to the parent plant.
The embryo emerges out of the fruit with a massive radicle pointing downwards. Due to increased weight, the seedling separates from the parent plant and estbalishes itself in the muddy soil below.