Control and Coordination — Part 2: Plants and hormones: visual lesson, CBSE Class 10 Science

Lesson

Coordination in plants and hormones in animals

Part 2 — how plants respond without a nervous system, and how chemical messengers coordinate both plants and animals.

In this lesson you will

Distinguish immediate responses, such as in touch-me-not, from growth-dependent tropic movements
Describe phototropism, geotropism, hydrotropism, chemotropism and thigmotropism with examples
State the roles of auxins, gibberellins, cytokinins and abscisic acid
Match endocrine glands with their hormones and functions, and explain feedback regulation

Concept

Two kinds of movement in plants

Plants respond in two ways: immediate movements that do not involve growth, and slow growth movements in which one side of an organ grows more than the other.

Table comparing immediate plant responses with growth movements by speed, growth, mechanism and example
	Immediate response	Growth movement
Speed	Seconds	Hours or days
Growth involved?	No	Yes
How it happens	Cells change shape by gaining or losing water	Unequal growth on two sides
Example	Touch-me-not leaves folding	Shoot bending towards light

Diagram

Touch-me-not: a quick response

When a touch-me-not (Mimosa pudica) leaf is touched, its leaflets fold and droop within seconds. Information passes from cell to cell by electrical-chemical signals, and cells at the base of the leaflets lose water, change shape, and the leaflets fold.

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