Class 10 Transpiration Mock Test (ICSE)

Topics in Transpiration

• Types of transpiration
• Mechanism of stomatal opening and closing
• Factors affecting transpiration
• Experiments on transpiration
• Significance and guttation

Transpiration practice questions with answers

1. Q1Multiple choice·1 mark
   Cobalt chloride paper test is typically used in transpiration experiments to demonstrate:

   1. (a)Absorption of water by roots
   2. (b)Release of oxygen during photosynthesis
   3. (c)Difference in the rate of transpiration between the upper and lower surfaces of a leaf
   4. (d)Upward movement of sap in the stem
   Show answer and step marks

   1. Correct option: (c) Difference in the rate of transpiration between the upper and lower surfaces of a leaf+1

   Answer: (c)
2. Q2Multiple choice·1 mark
   The type of transpiration that accounts for the maximum percentage of total water loss in a typical herbaceous plant is:

   1. (a)Lenticular transpiration
   2. (b)Stomatal transpiration
   3. (c)Bark transpiration
   4. (d)Cuticular transpiration
   Show answer and step marks

   1. Correct option: (b) Stomatal transpiration+1

   Answer: (b)
3. Q3Multiple choice·1 mark
   Guttation typically occurs through specialized structures called:

   1. (a)Cuticle
   2. (b)Stomata
   3. (c)Lenticels
   4. (d)Hydathodes
   Show answer and step marks

   1. Correct option: (d) Hydathodes+1

   Answer: (d)
4. Q4Multiple choice·1 mark
   According to the potassium ion concentration theory, the opening of stomata is caused by the inward movement of $K^+$ ions into guard cells, resulting in:

   1. (a)Decrease in turgor pressure of guard cells
   2. (b)Flaccidity of guard cells
   3. (c)Increase in water potential of guard cells
   4. (d)Increase in turgor pressure and opening of the stoma
   Show answer and step marks

   1. Correct option: (d) Increase in turgor pressure and opening of the stoma+1

   Answer: (d)
5. Q5Long answer·4 marks
   With reference to the laboratory experiments conducted to study transpiration: (a) Name the apparatus commonly used to measure the rate of water intake by a cut plant shoot. State the underlying principle of this apparatus. (b) Mention any two important precautions that must be taken while setting up this apparatus to ensure accurate results.
   Show answer and step marks

   1. (a) Apparatus: Potometer (e.g. Ganong's potometer or Farmer's potometer).+1
   2. (a) Principle: the rate of water uptake by a cut shoot is approximately equal to the rate of transpiration.+1
   3. (b) First precaution, any one of: cut the shoot obliquely under water so no air enters its xylem; make all joints airtight with Vaseline or grease; ensure there is no air bubble in the apparatus apart from the one index bubble; keep the leaves dry and the shoot fresh; or any other valid precaution.+1
   4. (b) Second precaution, a different one from the same list.+1

   Answer: (a) Ganong's (or Farmer's) potometer; water uptake by a cut shoot is approximately equal to the water lost in transpiration. (b) Any two of: cut the shoot under water, make all joints airtight with Vaseline, keep no air bubbles except the index bubble, keep the leaves dry.
6. Q6Long answer·4 marks
   Answer the following questions regarding plant water relations: (a) Explain two major physiological significances of transpiration to plants. [2] (b) State the conditions under which guttation takes place in plants and mention the composition of the liquid droplet lost during this process. [2]
   Show answer and step marks

   1. (a) Significance 1: Transpiration creates a suction force (transpiration pull) that facilitates the ascent of sap, enabling the upward transport of water and dissolved minerals from the roots to aerial parts.+1
   2. (a) Significance 2: It provides a necessary cooling effect to the plant body, preventing overheating and damage to delicate tissues on hot sunny days.+1
   3. (b) Conditions for guttation: It occurs when root pressure is exceptionally high and transpiration is very low or absent, commonly observed during early mornings or nights under high humidity.+1
   4. (b) Composition of liquid: The liquid lost is a dilute aqueous solution containing various dissolved organic and inorganic salts, rather than pure water.+1

   Answer: (a) Transpiration creates the transpiration pull that drives the ascent of sap (water and minerals from roots to aerial parts), and it cools the plant on hot days. (b) Guttation occurs when root pressure is high and transpiration is low, as on humid nights and early mornings; the droplets are water containing dissolved salts and organic substances, not pure water.

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