Primary growth in plants




   In plants, growth starts from the germination of seeds. Then it develops internally and externally forming various parts.

Plants undergoes primary and secondary growth which differs from each other in many ways.
Primary growth in plants exhibits in plants within 1 year then plant undergoes secondary growth.

PRIMARY GROWTH IN PLANTS:

Primary growth in plants takes place inside the stem. Both dicotyledenous and monocotyledenous plants undergoes primary growth, and of course they show some variations.

IN DICOTYLEDENOUS PLANTS:

Stem consist of three zones. They are:

1.EPIDERMIS

2.GROUND TISSUE

3. STELE

1.EPIDERMIS:

It is the outermost layer covered by cuticle.

Epidermis protects the inner parts of the stem.

Cuticle covers the epidermis and helps in transpiration.

It may have trichomes and stomata.

2. GROUND TISSUE:

The tissues other than vascular bundles and epidermis is considered as ground tissue. It is again divided into three sub zones. they are:

A)Hypodermis
B)Cortex
C)Endodermis

Hypodermis consist of collenchymatous cells which provide mechanical support to the plant.

Cortex contains parenchymatous cells and having intercellular spaces inside it.

Endodermis is next to the cortex. Innermost layer containig starch sheath and abundant starch grains in it.

3.STELE

It consist of three sub zones. They are:

A)Pericycle
B)Vascular bundles
C)Pith

Pericycle  is next to endodermis. it is arranged like a circle above the vascular bundles.

Vascular bundles consist of xylem and phloem elements and these two get separated by vascular cambium. These are arranged in a ring like manner conjoint, open(presence of vascular cambium), Endarch.

Pith is the innermost and present in the central region having parenchymatous cells with intercellular spaces.

                                  Related image

IN MONOCOTYLEDENOUS PLANTS:

Monocot plants having the similar primary growth but they exhibit few differences. They are:

Having sclerenchymatous bundle sheath in hypodremis.

Vascular bundles does not have cambium. It is conjoint and closed.Water containing cavities are present in vascular bundles.
Vascular bundles are arranged in a scattered manner. Peripheral are small and centrally located are large in size.

                                              Related image

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