Control and Coordination in plants CBSE Class X Science Lesson by Soma Mukhopadhyay.CBSE Biology Class 10 Science lesson Control and Coordination in Plants.
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CONTROL AND COORDINATION IN PLANTS
MOVEMENTS OR CHANGES IN POSITION ARE AN IMPORTANT CHARACTERISTIC OF LIVING BEINGS-THEY MAY BE DUE TO THE GROWTH OR CHANGES MADE IN THE INTERNAL BODY COMPONENTS WITH RESPECT TO ONE ANOTHER.
BUT MOVEMENTS ARE NOT HAPHAZARD OR SECLUDED.THEY ARE HIGHLY CONTROLLED AND COORDINATION.
CONTROL IS THE POWER TO RESTRAIN AND REGULATION BY WHICH SOMETHING CAN BE STARTED, SLOWED DOWN, EXPEDITED OR STOPPED.
COORDINATION IS AN ORDERLY OR HARMONIOUS WORKING OF DIFFERENT BUT INTER RELATED PARTS SO AS TO PERFORM ONE OR MORE ACTIVITIES VERY SMOOTHLY.
THERE ARE TWO MODES OF CONTROL AND COORDINATION IN LIVING BEINGS —
CHEMICAL AND NERVOUS
Animals HAVE A NERVOUS SYSTEM AND A CHEMICAL SYSTEM.
Plants DO NOT HAVE A NERVOUS SYSTEM.THEY USE THE CHEMICAL SYSTEM.
The plants coordinate their behavior against environmental changes by using hormones.
The hormones in plants called Phytohormones co-ordinate their behavior by affecting the growth of a plant. The growth movement can be directional as in tropism and non-directional as in nasties.
And the effect on growth of the plant can result in the movement of a part of the plant like shoot or root, etc.
The plants respond to various stimuli very slowly by growing due to the absence of nervous system.
AUXINS : Auxins are the plant hormones which promote cell enlargement and differentiation in plants. Auxins also promote fruit growth.
GIBBERELLINS : Gibberellins are plant hormones which promote cell enlargement and differentiation in the presence of auxins. Gibberellins help in breaking the dormancy in seeds and buds.They also promote growth in fruits.
CYTOKININS : Cytokinins are the plant hormones which promote cell division in plants. Cytokinins also help in breaking the dormancy of seeds and buds. They delay the ageing in leaves. Cytokinins promote the opening of stomata. They also promote fruit growth.
ABSCISIC ACID (ABA) : Abscisic acid is a plant hormone which functions mainly as a growth inhibitor. Abscisic acid promotes the dormancy in seeds and buds ( this is the opposite of breaking of dormancy). It also promotes the closing of stomata. Abscisic acid promotes the wilting and falling of leaves. It also causes the detachment of flowers and fruits from the plants.
FUNCTIONS OF PLANT HORMONES
Germination of seeds (or breaking the dormancy of seeds).
Growth of root, stem and leaves..
Movement of stomata (or stomatal movement) in leaves.
Flowering of plants.
Ripening of fruits.
Phototropism, geotropism, chemotropism,hydrotropism, thigmotropism and nastic movements.
POSITIVE AND NEGATIVE PHOTOTROPISM
Shoot shows positive phototropism as they move towards light
Root shows negative phototropism as they move away from light
Root shows positive geotropism.
Shoot shows negative geotropism
Movement of a plant part in response to a chemical stimulus is called chemotropism.
Here the pollen tube grows towards the sugary substance (chemical) secreted by the ripe stigma of carpel in the flower.
The movement of a plant part in response to water is called hydrotropism.
Root shows positive hydrotropism
Shoot shows negative hydrotropism.
The directional growth movement of a plant part in response to the touch of an object is called thigmotropism.
Tendrils are positively thigmotrophic.
The non-directional movement of a plant part in response to the touch of an object is called thigmonasty.
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