In-text Questions — Plant Hormones — Control and Coordination

1. 11 markNCERT Cl-10 Science, In-text Qs after §6.2's hormone discussion, Q1

   What are plant hormones?

   Hint. Note where they're made versus where they act — those are two different places.

   Step 1 — Define the term. Plant hormones (phytohormones) are chemical substances that help coordinate growth, development and responses to the environment in plants.

   Step 2 — Note how they travel. They are synthesised at one place in the plant and simply diffuse to the area where they act, since they aren't produced locally where they're needed.

   ✦ Answer: Plant hormones are chemicals that coordinate growth, development and environmental responses in plants — made in one part of the plant and diffusing to act in another.

   Where students slip. Assuming plant hormones act right where they're made — the chapter specifically notes they're synthesised away from their site of action and diffuse there.

2. 22 marksNCERT Cl-10 Science, In-text Qs after §6.2's hormone discussion, Q2

   How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

   Hint. One movement involves growth and takes days; the other involves no growth at all and happens almost instantly.

   Step 1 — Describe the sensitive plant's leaf movement. This movement is immediate and involves no growth at all — specialised cells rapidly change shape by changing their water content (swelling or shrinking), causing the leaves to droop.

   Step 2 — Describe the shoot's movement toward light. This movement is slow and depends entirely on growth — auxin causes cells on the shadier side of the shoot to elongate more than cells on the lit side, so the shoot bends toward the light over time.

   Step 3 — State the key contrast. If growth were stopped, the shoot would no longer bend toward light, but the sensitive plant's leaves would still respond to touch just as quickly, since that movement never depended on growth in the first place.

   ✦ Answer: The sensitive plant's leaf movement is immediate and growth-independent (cells changing water content); a shoot's movement toward light is slow and entirely growth-dependent (unequal cell elongation on the two sides).

   Where students slip. Treating both as the 'same kind' of plant movement because both look directional — one is a rapid, growth-free response; the other is a slow, growth-based one, and the mechanisms are entirely different.

3. 31 markNCERT Cl-10 Science, In-text Qs after §6.2's hormone discussion, Q3

   Give an example of a plant hormone that promotes growth.

   Hint. Three of this chapter's four plant hormones promote growth — only one inhibits it.

   Step 1 — Recall which hormones promote vs. inhibit growth. Auxin, gibberellins and cytokinins all promote growth in different ways; abscisic acid inhibits growth instead.

   Step 2 — Give one example. Auxin promotes cell elongation, since it's this elongation that helps shoots grow and bend toward light.

   ✦ Answer: Auxin (or gibberellins, or cytokinins) — any hormone other than abscisic acid, which inhibits rather than promotes growth.

   Where students slip. Naming abscisic acid as a growth-promoter — it's specifically the growth-inhibiting hormone in this chapter's list.

4. 42 marksNCERT Cl-10 Science, In-text Qs after §6.2's hormone discussion, Q4

   How do auxins promote the growth of a tendril around a support?

   Hint. Think about which side of the tendril touches the support, and which side doesn't.

   Step 1 — Recall what happens on contact. When a tendril touches a support, the part of the tendril in contact with the object grows more slowly than the part away from it.

   Step 2 — Explain the role of auxin. Auxin promotes cell elongation, and since it accumulates more on the side away from the object, that side grows faster than the touching side.

   Step 3 — Explain the result. This unequal growth rate on the two sides makes the tendril curve and circle around the object, allowing it to cling to the support.

   ✦ Answer: Auxin causes the side of the tendril away from the support to elongate faster than the touching side, and this unequal growth curls the tendril around the support.

   Where students slip. Assuming both sides of the tendril grow at the same rate — the whole mechanism depends on unequal growth between the touching and non-touching sides.

5. 53 marksNCERT Cl-10 Science, In-text Qs after §6.2's hormone discussion, Q5

   Design an experiment to demonstrate hydrotropism.

   Hint. Copy the logic of the phototropism activity earlier in the chapter, but swap the light source for a one-sided water source.

   Step 1 — Set up the germinating seeds. Take a shallow tray of soil and plant a few freshly germinated seeds in the centre, well away from any obvious water source.

   Step 2 — Create a one-sided moisture gradient. Place a small perforated pot filled with water, or a wad of wet cotton, into the soil at one side of the tray only — away from the seedlings — while keeping the rest of the soil comparatively dry, so moisture diffuses through the soil mainly from that one side.

   Step 3 — Observe over several days. Leave the tray undisturbed for a few days and observe the direction the roots grow in.

   Step 4 — State the expected result and conclusion. The roots will bend and grow toward the side with the wet cotton/water source, even if this isn't straight down — showing that roots respond directionally to a moisture gradient (hydrotropism), the same way shoots bent toward light in the earlier phototropism activity.

   ✦ Answer: Germinate seeds in soil with a wet-cotton or perforated-water-pot moisture source placed at just one side (not below the seedlings). Over a few days, the roots bend toward that side rather than growing straight down, demonstrating hydrotropism.

   Where students slip. Watering the soil evenly from all sides — that gives the roots no directional gradient to respond to; the water source must specifically be placed to one side to create the asymmetry the experiment needs.

Solutions written by the tuition.in editorial team and checked against the NCERT Class 10 Science textbook, Reprint 2026-27 (jesc106.pdf) — three in-text question sets (14 questions total) plus one end-of-chapter Exercise (12 questions). Unchanged by rationalisation, though the chapter examines the brain as fore-brain/mid-brain/hind-brain (never 'cerebrum') and covers only four plant hormones (auxin, gibberellins, cytokinins, abscisic acid — no ethylene) and six animal hormones (no glucagon or progesterone).. Questions are referenced from the NCERT textbook for identification.