Plant Physiology – Transport in Plants Quiz - ICSE Class 11 Biology

Free practice quiz: Plant Physiology – Transport in Plants (ICSE Class 11 Biology). 36 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. The opening and closing of stomata are primarily regulated by the movement of which ion?

   1. Sodium (Na+)
   2. Potassium (K+)
   3. Calcium (Ca2+)
   4. Magnesium (Mg2+)
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   Answer: B. Potassium (K+)

   The influx of potassium ions into guard cells leads to an increase in turgor pressure, causing stomatal opening. Efflux of potassium ions leads to a decrease in turgor pressure and stomatal closure.

2. The movement of water into root hairs is primarily driven by:

   1. Active transport of water molecules
   2. Bulk flow due to wind action
   3. A difference in water potential between the soil solution and the root hair cytoplasm
   4. Evaporation from the root surface
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   Answer: C. A difference in water potential between the soil solution and the root hair cytoplasm

   Water moves from an area of higher water potential (usually the soil) to an area of lower water potential (the root hair cytoplasm, which has a more negative water potential due to dissolved solutes). This movement is passive, driven by osmosis.

3. Which of the following conditions would MOST likely lead to reduced transpiration?

   1. High humidity, low temperature
   2. Low humidity, high wind
   3. High temperature, low humidity
   4. High light intensity, low CO2
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   Answer: A. High humidity, low temperature

   High humidity reduces the water potential gradient between the leaf interior and the atmosphere, slowing down evaporation. Low temperatures also generally reduce the rate of evaporation. Conversely, low humidity, high wind, and high temperature all increase the rate of transpiration.

4. Root pressure is most significant in plants under conditions of:

   1. High transpiration and low humidity
   2. Low transpiration and high humidity
   3. High wind speed and high temperature
   4. Low soil water potential
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   Answer: B. Low transpiration and high humidity

   When transpiration is low, water absorption by roots can continue, building up positive hydrostatic pressure in the xylem, known as root pressure. This is more pronounced when the atmosphere is humid, reducing the transpiration pull.

5. Which of the following factors is LEAST likely to affect the rate of transpiration?

   1. Wind speed
   2. Light intensity
   3. Soil pH
   4. Atmospheric humidity
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   Answer: C. Soil pH

   Soil pH primarily affects nutrient availability and absorption. While severe nutrient deficiency can indirectly impact plant health and transpiration, soil pH itself does not directly influence the physical process of water evaporation from leaves. Wind speed, light intensity, and humidity directly affect the rate of transpiration.

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