NCERT Solution for Class 10 Science Chapter 7
Control and Coordination
NCERT Books for Session 2020-2021
CBSE Board and UP Board
Exercises Questions
Page No-126
Questions No-8
How does chemical coordination occur in plants?
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Animals have a nervous system for controlling and coordinating the activities of the body. But plants have neither a nervous system nor muscles. Plants respond to stimuli by showing movements. The growth, development, and responses to the environment in plants is controlled and coordinated by a special class of chemical substances known as hormones. These hormones are produced in one part of the plant body and are translocated to other needy parts. For example, a hormone produced in roots is translocated to other parts when required. The five major types of phytohormone are auxins, gibberellins, cytokinins, abscisic acid, and ethylene. These phytohormones are either growth promoters (such as auxins, gibberellins, cytokinins, and ethylene) or growth inhibitors such as abscisic acid.
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Plant hormones play their roles in chemical coordination. Most of the plant hormones promote growth in certain plant parts, e.g. auxin, gibberellins and cytokinin. Abscissic acid is a plant hormone which inhibits growth. Shedding of leaves or ripe fruits is facilitated by abscissic acid.
Chemical coordination in plants is brought about by plant hormones also knows as phyto-hormones. These hormones either promote growth or inhibit it. Five major types of plant hormones are auxin, gibberellin, cytokinin, abscisic acid and ethylene. Auxin, gibberellin and cytokinin are referred as growth promoters whereas abscisic acid and ethylene are growth inhibitors. certain physiological processes like seed germination and flowering respond to the daily duration of light hours or photoperiods. Plants respond to this photoperiodic stimulus by a specialised chemical called phytochrome.