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The passage of water through a plant is known as the transpiration stream - Leaving Cert Biology - Question a - 2005
Question a
The passage of water through a plant is known as the transpiration stream. Answer the following questions in relation to the transpiration stream. (i) Explain how w... show full transcript
Worked Solution & Example Answer:The passage of water through a plant is known as the transpiration stream - Leaving Cert Biology - Question a - 2005
Step 1
Explain how water enters the plant at the root hair.
Answer
Water enters the plant via root hairs through a process called osmosis. The root hair cells have a selectively permeable membrane that allows water to move from the soil, where there is a higher concentration of water, to the inside of the root hair, where the concentration of water is lower. This occurs due to the difference in water potential, allowing water to be absorbed efficiently.
Step 2
Do minerals enter the plant by the process that you have indicated in (i)? Explain your answer.
Answer
No, minerals do not enter the plant by osmosis. While water does enter through osmosis, minerals typically enter via active transport. This process requires energy to move minerals against their concentration gradient from the soil into the root cells.
Step 3
How is xylem adapted for its role in water transport?
Answer
Xylem is uniquely adapted for its role in water transport through features such as its tubular structure, which allows for continuous movement of water. The walls of xylem vessels are reinforced with lignin, making them sturdy and capable of withstanding the pressure of water. The narrow diameter of xylem vessels facilitates the lateral movement of water and helps maintain a continuous column of water.
Step 4
Give an account of the importance of these forces in raising water to great height in trees.
Answer
The strong forces of attraction between water molecules, known as cohesion, are crucial in raising water to great heights in trees. This cohesion leads to the formation of a continuous column of water within the xylem. As water evaporates from the leaves during transpiration, it creates a negative pressure that pulls up more water from the roots. This upward pull, combined with the cohesive properties of water, ensures the efficient transport of water throughout the tree.