8 1 transport in plants

Xylem are vessels that transport water and mineral ions from the roots to the upper parts of plants.

True. Xylem vessels are strong to enable them to transport water without breaking; this means that they also contribute to structural support within plant stems.

The phloem is a tissue that transports sucrose and amino acids around plants.

True. The xylem tissue forms a cross shape in the centre of roots, and the phloem surrounds the xylem tissue.

Xylem tissue is represented by pink regions in the diagram. This is because phloem is on the outside of the vascular bundles in a stem, while xylem is on the inside.

The types of plant tissue represented by A and B are: The diagram shows a leaf cross section. Xylem tissue is closer to the upper surface of leaves while phloem is closer to the lower surface.

Xylem vessels are adapted to their function as follows:

The cell type shown in the image is a root hair cell.

The role of a root hair cell is to absorb water and mineral ions from the soil.

Root hair cells are adapted for absorption of water and minerals as follows:

The pathway taken by water as it travels across the root, up the stem, and out of the leaves of plants is: Root hair cells root cortex xylem vessels spongy mesophyll cells

False. Placing a celery stem in food colouring and allowing it to absorb the dye allows the location of the xylem to be seen.

Transpiration is the loss of water vapour from the leaves of plants by evaporation.

The spongy mesophyll cells are involved in transpiration as follows:

Water vapour exits the leaf air spaces by the process of diffusion through the stomata.

The piece of equipment used to measure transpiration rate in a plant shoot is known as a potometer.

A bubble potometer works to measure transpiration rate as follows:

An airtight potometer system can be ensured as follows:

The effect of wind speed on transpiration rate can be investigated by setting up a fan or hairdryer blowing air over the plant shoot at different speeds.

Environmental variables that should be kept the same when investigating the effect of temperature on transpiration rate include:

The structure of the spongy mesophyll layer aids transpiration as follows:

The relationship between number of stomata and transpiration rate is as follows:

Transpiration pull occurs when water is drawn up the xylem to replace the water that is lost from the surface of spongy mesophyll cells by evaporation.

Forces of attraction between water molecules enables transpiration pull because:

True. At higher temperatures water molecules have more kinetic energy and are more likely to diffuse out via the stomata.

Transpiration is faster on a windy day because wind blows water vapour away from the surface of leaves, maintaining a water vapour concentration gradient between the inside and the outside of leaves.

False. Increasing humidity levels will decrease the rate of transpiration. This is because humid conditions decrease the water vapour concentration gradient between the inside and outside of the leaf.

The water vapour concentration gradient is the difference in water vapour concentration between the inside and the outside of a leaf.

Plants wilt when they lose water and cannot replace it with water from the soil. The water loss causes the plant cells to lose their rigid structure and the cell walls no longer provide support to the plant.

Translocation is the movement of sucrose and amino acids through phloem tissue from sources to sinks.

A source is a part of the plant that produces or releases sucrose or amino acids.

A sink is a part of a plant that uses or stores sucrose or amino acids.

True. Sources and sinks can be in different parts of plants depending on whether plants are photosynthesising or relying on stored sucrose.

Phloem transport occurs in different directions depending on the time of year: