20 points Transport in plants
Answer all the questions
1. a)State three ways in which the root hairs are adapted to their function.(3mks).
b) Draw a well labelled diagram of a root hairs cell.(3mks).
2.List three ways in which the Xylem vessels are adapted to their function. (3mks).
3.Name two processes by which mineral salt are taken up by the plants (2mks).
4 Briefly explain water is absorbed by plants. (9mks).
Class comments

Explanation:

1. A)Plants absorb water from the soil by osmosis. Root hair cells are adapted for this by having a large surface area to speed up osmosis. The absorbed water is transported through the roots to the rest of the plant where it is used for different purposes. They have a large surface area, due to their hair-like projections, which eases uptake.

B) refer the picture

2. The end walls are removed from each end, forming an uninterrupted tube, so water can pass through easily.Their walls are thickened with a woody substance called lignin, which helps to support the xylem vessels and stops them collapsing inwards.There are small pits in the cell wall where is no lignin so water and ions can move into and out of the vessels.

3. They absorb mineral ions by active transport, against the concentration gradient. Root hair cells are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption.

4. Plants absorb water through their entire surface – roots, stems and leaves because of this osmosis occurs and the water is absorbed by the root hairs through cell membranes from the soil. Then the root hair cells become more turgid and their osmotic pressure falls.

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