Structure of Transport Tissues (CIE AS Biology)

Fig. 1 shows a cross-section through a mature buttercup root taken using a light microscope under high power.

Fig. 1

Identify X, Y, and Z.

Explain how the structure of tissue X is related to its function.

Water moves along structure X in a continuous column.

Explain how the structure of water molecules enables this.

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

Fig. 1

Identify and explain an adaptation of xylem vessels visible in Fig. 1.

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.

Explain why it is important that one of the daughter cells (cell E) is a 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 shows the structure of plasmodesmata, channels that exist between some types of plant cell that allow the transport of substances.

Fig. 1

Suggest why plant cells need plasmodesmata while animal cells do not.

Within the cytoplasm of the plasmodesmata is a structure known as the desmotubule; a column of specialised endoplasmic reticulum that connects to the cell surface membrane via a series of actin and myosin proteins. Actin and myosin proteins are the contractile elements of animal muscle cells.

Suggest a possible function of the desmotubule.

State the location of plasmodesmata in the vascular tissue of plants and describe its role there.

Other than the role of plasmodesmata described in part (c), give three substances that might move from one cell to another via plasmodesmata.

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. 

Evaluate this statement. 

Cellulose is the most abundant organic polymer on Earth.

Use your knowledge of plant structure to suggest which compound ranks number 2 in the list of abundant organic polymers.

Give a reason for your choice.

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

Explain how this helps it to perform one of its functions.