Science · Class 10

Active learning ideas

Plant Hormones: The Chemical Messengers

Ever wondered how a plant in a dark room can find the smallest crack of light? Let's uncover the secrets of the plant world's own chemical messengers that direct their every move and milestone.

• CBSE Learning Outcomes
• NCERT: Class 10 - Chapter 7 - Hormones in Plants

• 10–20 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Concept Mapping
• 20 min · Small Groups

The Light Maze Challenge

Students grow a bean seedling inside a shoebox with internal partitions creating a maze. A single hole allows light in at one end, and students observe how the plant stem navigates the maze towards the light over a week, demonstrating phototropism.

Explain the role of auxin in phototropism.

Facilitation Tip

Ensure the box is completely sealed with black paper or tape to prevent any stray light from entering.

What to look for

Conduct a 'Hormone Hot Seat' activity. One student takes the role of a hormone (e.g., Auxin) and other students ask questions about its functions, location, and effects.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 02

• Concept Mapping
• 15 min · Pairs

To Pinch or Not to Pinch

Using two identical potted plants like marigold or coleus, students pinch off the apical bud of one plant. They then observe both plants for two weeks to see how removing the auxin source in the pinched plant promotes the growth of lateral branches, demonstrating apical dominance.

Compare the functions of gibberellins and cytokinins in plant growth.

Facilitation Tip

Use fast-growing plants so that the results are clearly visible within a short timeframe.

What to look for

A short test including a diagram of a plant bending towards a window, where students must explain the phenomenon by labelling the distribution of auxin and the resulting cell elongation.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

Activity 03

• Concept Mapping
• 10 min · Individual

Ripen it Right!

Students place an unripe tomato or chikoo in a sealed paper bag with a ripe banana, and another similar unripe fruit in the open. They compare the rate of ripening over a few days to understand the effect of ethylene gas.

Justify why abscisic acid is known as the stress hormone.

Facilitation Tip

Ask students to record daily observations on colour, texture, and smell to make the comparison more scientific.

What to look for

Provide students with a worksheet containing a table with two columns: 'Plant Phenomenon' (e.g., seed germination, fruit ripening) and 'Hormone Responsible'. Students have to fill in the blanks.

• Understand
• Analyze
• Create
• Self-Awareness
• Self-Management

A few notes on teaching this unit

Begin with observable phenomena like a sunflower tracking the sun or a plant bending towards a window. Use analogies, comparing hormones to remote controls for plant functions. Hands-on experiments like observing seed germination or phototropism in a box are crucial to make these invisible processes tangible and memorable for students.

By the end of these activities, students will be able to explain how specific hormones act as signals to control plant growth, movement, and survival strategies.

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Watch Out for These Misconceptions

• Plants do not move because they are fixed in the soil.

  While plants are fixed, they show two types of movements: growth-dependent (tropic) movements like bending towards light, and growth-independent (nastic) movements like the folding of a 'touch-me-not' plant's leaves. Hormones control these movements.

• All plant hormones are 'growth hormones' that make plants bigger.

  Not all hormones promote growth. While auxins and gibberellins are growth promoters, hormones like Abscisic Acid (ABA) are growth inhibitors. ABA causes seed dormancy and the closing of stomata, which are crucial for survival during stressful conditions.

• Plant hormones are produced in special glands, just like in humans.

  Unlike animals, plants do not have specialized glands to produce hormones. Phytohormones are produced in cells in specific regions, like the tips of shoots and roots, and then transported to other parts where they act.

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Methods used in this brief

• Concept Mapping