Structure of Transport Tissues (CIE A Level Biology)

Fig. 1 shows a cross-section through a leaf viewed at a magnification of x250.

Fig. 1

Calculate the actual size of a palisade mesophyll cell shown in Fig. 1.

Show your working and include appropriate units.

Contrast the structures of the tissues labelled P and Q in Fig. 1.

A student viewed a section of plant tissue under a light microscope. The tissue viewed is shown in Fig. 2.

Fig. 2

Draw a low-power plan diagram of the plant tissue shown in Fig. 2.

The vascular system of plants has been likened to the circulatory system in animals such as humans. 

Discuss the idea that the plant vascular system and the human circulatory system are comparable. 

Cellulose is the most abundant organic polymer on Earth.

Use your knowledge of plant structure to suggest which compound ranks second in the list of abundant organic polymers.

[1]

(ii)

Explain your answer to part (i).

[1]

The compound referred to in part (b) is highly hydrophobic in nature.

Suggest how this helps it to carry out its role.

Lignin is an organic polymer found within the cell walls of plants. Fig. 1 shows several arrangements that can be formed by lignin within xylem cell walls.

Note that the lignin is represented by dark grey areas, while non-lignified regions are shown in light grey.

Fig. 1

Suggest possible advantages of the different lignin arrangements found in plants.

Fig. 2 below shows a section of vascular tissue in a woody plant stem.

Public domain, via Flickr

Fig. 2

Fig. 2 shows the following features:

• Tracheids
• Xylem vessels
• Bordered pits
• Parenchyma cells

Note that tracheids are tapered vessels with closed ends that transport water.

Use the information provided and your own knowledge to add labels to Fig. 2 that show the locations of the four features listed above.

Use Fig. 2 to produce a biological drawing that shows at least three different structures within the vascular tissue.

Fig. 1 shows a transverse section of xylem tissue viewed under a light microscope.

Fig. 1

Identify an adaptation of xylem vessels that is visible in Fig. 1.

[1]

Explain how the feature identified in part (i) aids xylem vessel function.

[2]

Fig. 1 was generated using a light microscope.

Explain why light microscopes have a lower maximum magnification than electron microscopes.

Xylem vessels are distributed differently in different parts of plants.

Describe the distribution of xylem tissue in the stems, roots, and leaves of dicotyledonous plants.

Meristematic tissue is found in the growing regions of plants, such as shoot tips. Meristematic cells have a similar role to stem cells in animals.

Fig. 1 shows some of the stages in the formation of a mature phloem sieve tube element and companion cells from a meristematic cell.

Fig. 1

Cells E and F in Fig. 1 are daughter cells produced when the meristematic cell divides in the shoot tip.

Suggest why it is important that one of the daughter cells (cell E) is another meristematic cell.

Complete Table 1 to describe the changes that are shown in Fig. 1 between stages:

• F and G
• G and H
• H and J.

Table 1

Explain how the structure of a mature sieve tube element is related to its function.

Describe the functions of companion cells in transport in the phloem.

Fig. 1 below shows a micrograph of part of a leaf.

Berkshire Community College, CC0, via Wikimedia Commons

Fig. 1

The leaf shown in Fig. 1 is upside down.

Explain how we can see from the image that this is the case.

Structures R and S in Fig. 1 make up a single vascular bundle.

Describe the distribution of vascular bundles in a leaf.

Explain why structures R and S are present in the leaves of plants.

A student produced a low-power plan diagram of Fig. 1.

State the leaf features that would be visible on the student's diagram.