Germination

Introduction

It is the beginning of growth from a seed. It starts with the absorption of water. It results in the rapid increase in weight and to a swelling of the tissues which in turn ruptures the seed coat (testa) allowing the embryonic root and shoot to emerge out.

• Embryonic root is called radicle.
• Embryonic shoot is called plumule.

Germination takes place when all the necessary conditions of soil like pH, oxygen, water and temperature are provided. First we can observe the swelling of the seed by absorption(imbibition) of water. The seed coat called testa will burst out. Some physiological process like respiration and enzyme secretion too begins by the absorption of water. The insoluble foodstored in the cotyledon is made simple and soluble and is diluted by water. Later it is conducted to the growing embryonic parts.

Two types of germinations are

• Epigeal germination
• Hypogeal germination.

Hypocotyl region: It is the region between the radicle and the node of the growing seed. Epicotyl region: It is the region between the plumule and the node of the growing seed. Seed consists of either one cotyledon (monocot) or two cotyledon (dicot)

Epigeal germination: Epi means above geal mean soil. The hypocotyl grows first and pushes the cotyledonary node and other parts of the seed out of the soil..E.G Beans

Hypogeal germination: Hypo mean below and geal means soil. of the seed out of the soil..E.G Beans

Hypogeal germination: Hypo mean below and geal means soil. Here the epicotyl grows first and pushes only the plumule out of the soil. Other parts remain inside the soil. Eg. Paddy