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PIGMENTS: Pigments are the substances that have an ability to absorb the light at different wavelengths. There are four types of pigments in plant. They are: 1.Chlorophyll a- (bright or blue-green) 2.Chlorophyll b-(yellow green) 3.Xanthophylls-(yellow) 4.Carotenoids-(yellow to yellow-orange)  * Chlorophyll a is the most abundant pigment responsible for trapping light. Other pigments are accessory pigments which protect chlorophyll a from photo-oxidation .

   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