We water the soil but it reaches the topmost leaves of the plants. Explain in brief the process involved.
We water the soil but it reaches the topmost leaves of the plants. Explain in brief the process involved.
The process of water reaching the topmost leaves of a plant from the soil involves two main mechanisms working in the xylem vessels:
- Active Absorption and Root Pressure:
- Cells in the roots take up ions from the soil actively, creating a difference in concentration of these ions between the root and the soil.
- Water moves into the root from the soil to eliminate this difference, creating a continuous column of water that is pushed upwards. This is known as root pressure, which is mainly effective at night.
- Transpiration Pull (Major Driving Force during the day):
- During the day, water is constantly lost as water vapor from the stomata of the leaves through the process of transpiration.
- This evaporation of water molecules from the cells of a leaf creates a suction force (tension) that pulls water from the xylem cells of the roots up to the highest parts of the plant.
- This continuous upward suction ensures that water and dissolved minerals reach the topmost leaves of even very tall trees.
Marking Scheme
- 1Explanation of water absorption by roots and root pressure: 1 Mark
- 2Definition and explanation of transpiration (loss of water vapor from leaves): 1 Mark
- 3Explanation of transpiration pull creating suction to lift water to the top: 1 Mark
Hint
Think about how water evaporates from the leaves during the day and how this loss creates a suction force similar to drinking through a straw.
Quick Oral Answer
Water reaches the top of tall plants primarily due to transpiration pull, which is a suction force created by the evaporation of water from the leaves through stomata.
Analysis & Explanation
Water transport in plants does not rely on a muscular pump like the heart in animals. Instead, it uses physical forces. Root pressure provides a modest push from the bottom, which is sufficient for small plants or at night when transpiration is low. However, for tall trees, the primary driving force is transpiration pull. The evaporation of water from leaf surfaces creates a negative pressure (suction) in the xylem conduit, pulling the cohesive water column all the way from the roots to the topmost leaves.
Common Mistakes
- 1Students often mention translocation instead of transpiration. Translocation is the transport of food (photosynthates) via phloem, whereas water transport occurs via xylem through transpiration pull.
- 2Forgetting to mention the role of stomata in creating the suction pull.
Interesting Facts
A giant redwood tree can lift hundreds of liters of water daily to heights of over 100 meters without using any metabolic energy for the actual lifting process, relying entirely on solar-driven evaporation!
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2024?
This question carries 3 marks in the CBSE Class 10 Science 2024 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Life Processes" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Transportation in Plants" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2024 paper?
This is a Short Answer question from Section C in the CBSE Class 10 Science 2024 paper.