Chapter 6 Transport in Flowering Plants

Question 1

Define the term transpiration [1] (2010/A7)

Answer 1

Transpiration is the loss of water vapour from a plant, mainly through the stomata of the leaves

Question 2

Define the term translocation [2] (2013/A2)

Answer 2

Translocation is the transport of manufactured food substances, such as sucrose and amino acids, [1] through phloem, from the leaves to other parts of the plant. [1]

Question 3

Some weedkiller stop the plant form photosynthesising. These are often applied to the soil where the weeds are growing.
Explain how the weedkiller reaches its site of action in the leaves [4] (2013/A2)

Answer 3

1. The weedkillers dissolve in soil solution near the roots and these chemicals then diffuse into the root hair cells down a concentration gradient. [1]
2. The weedkillers diffuse through the inner cells of the roots into the xylem. [1]
3. In the xylem, it is carried along in water up the plant by capillary action, root pressure, but mainly though transpiration pull. This suction force is set up by the loss of water vapour from exposed surfaces of the plant. [1]
4. The chemicals reach the xylem in the leaf and diffuse into the mesophyll cells and then into the
   chloroplasts to stop photosynthesis. [1]

Question 4

Name one tissue present in the leaf vein and state how it is adapted to its function [2] (2014/A3)

Answer 4

Xylem :
- Lignified walls so that when bundled together can provide support
- No cross walls so that water can be transported unimpeded.
- No protoplasm – no blockage so that water can be transported easily.
Phloem:
- Sieve plate between sections of sieve tube so that materials can move easily
- Presence of companion cell – can respire and release energy for active transport of materials

Question 5

State the function of the root hair [2] (2016/A4)

Answer 5

• It absorbs water from the soil by osmosis [1]
• absorbs dissolved mineral salts from the soil by diffusion and active transport. / Anchor the plant firmly to the soil [1]

Question 6

Explain how root hairs are adapted to their functions. [2] (2016/A4)

Answer 6

• The root hair is a long and narrow protrusion of the root epidermal cell [1]
• to increase the surface area to volume ratio for faster absorption of water and dissolved mineral salts from the soil. [1]

Question 7

State the name and function of the xylem [2] (2016/A4)

Answer 7

• Xylem [1]
• to transport water and dissolved mineral salts from the
  roots to the leaves [1]