Plant Structure (Edexcel GCSE Biology)

Figure 1 shows part of a root as seen using a light microscope.

Figure 1

Figure 2 shows information about the two types of cells labelled in Figure 1.

Figure 2

(i) Calculate the surface area to volume ratio of the root hair cell. 

(2)

(ii) Explain how root hair cells are adapted for their function in the plant. 

(2)

Root hair cells can be viewed using an electron microscope. 

Describe and explain how the image in Figure 1 would appear different if taken using an electron microscope.

Figure 1 shows the mass of glucose produced in each layer of the leaf per hour.  

Figure 1

Describe the difference in the mass of glucose produced per hour in the palisade mesophyll and the mass of glucose in the spongy mesophyll shown in Figure 1. 

Using your understanding of the structure of the leaf, explain the data in Figure 2.

A student wanted to view the stomata on the underside of a leaf.

She completed a leaf peel as shown in Figure 1. 

Figure 1

The layer of nail varnish shows an impression of the cells on the lower surface of the leaf. 

Explain the function of the stomata in the leaf.

The student drew a biological drawing of the leaf peel taken from the underside of the leaf. 

Figure 2 shows this diagram.

Figure 2

State the number of stomata visible in Figure 2. 

On the underside of the leaf, the student found that they could see 30 stomata. 25 of these were open. 

(i) Describe how stomata open.

(3)

(ii) Calculate the percentage of stomata that were open. 

(2)

The student completed another leaf peel but of the upper surface of the leaf instead. 

They found that there were no stomata on the upper surface of the leaf.

Explain why it is an advantage to the plant to have this distribution of stomata on the upper surface of the leaf. 

Xylem and phloem are both types of vessels that transport substances through plants. 

During periods of drought, xylem and phloem can experience shrinkage. This can be observed by measuring the circumference of the trunks of trees. 

Figure 1 shows the difference in circumference of three trees before and after a seven day period of drought.

Figure 1

(i) Calculate the percentage decrease in the trunk circumference of Handroanthus chrysanthus before and after the period of drought. 

(2)

(ii) Handroanthus chrysanthus had a larger leaf surface area than Podocarpus oleifolius. 

Suggest why this might have led to a greater decrease in trunk circumference in the Handroanthus chrysanthus.

(2)

Figure 2 shows the structure of a xylem and a phloem vessel. 

Figure 2

(i) Name two substances that are transported in xylem vessels. 

(2)

(ii) Describe the features of a xylem vessel that make it adapted for its function in the plant. 

(2)

Figure 1 shows a cactus plant.

Figure 1

Describe two features that allow this plant to grow in hot, dry conditions. 

Another plant that is adapted for hot, dry conditions is marram grass (Ammophila arenaria). This species grows mostly in sand dunes where there is very little fresh water. 

Some of its adaptations are as follows:

• Leaves can roll up to reduce the surface area exposed to the wind

• Stomata are found in grooves within the protected inner part of the leaf

• Humid air is trapped within the protected inner part of the leaf, aided by small hairs

(i) Explain why it is beneficial for the plant to have these adaptations.

(2)

(ii) Suggest how this species could have evolved these adaptations. 

(3)

Marram grass is a plant that grows on exposed areas of sand dunes.

Figure 1 shows marram grass growing and a cross section through a leaf of marram grass.

Figure 1

Explain how marram grass is adapted to survive in the hot, windy and dry conditions of a sand dune.

Figure 1 shows how the leaves are arranged on a plant.

Figure 1

Which reason explains why the leaves are arranged in this way?

Figure 2 shows guard cells and stomata on the lower surface of a leaf.

A ruler has been overlayed on the image for scale purposes.

Figure 2

Use the ruler overlay to measure the length of the line on the labelled guard cell in mm.

The actual length of the labelled guard cell is 0.05 mm.

Calculate the magnification of this image.

Figure 3 shows the number of stomata per mm² on the lower surface of leaves from plants growing in soils with different water content.

Figure 3

Explain the difference in the number of stomata per mm² on the leaves of the plants grown in dry and wet soils.

Explain how palisade cells are adapted to their function.

A scientist saw the following query on a question and answer website:

"If plant leaf epidermis cells are the outermost cells in a leaf and closer to the sun, why do they not contribute much to photosynthesis?"

Suggest a suitable response to the query.

Explain how the leaf is adapted for gas exchange.

Sketch an annotated diagram of the cross-section of a leaf. You do not need to include the structures responsible for transport of food and water.

Which statement from A to D would indicate that transport of materials in the phloem involves metabolic processes rather than just a physical process?.

Figure 1 shows an aphid feeding on a plant stem.

Figure 1

Explain why they target structure X.

Describe how the xylem is adapted for the transport of water.

Compare the transport systems in plants and animals.