Use of the Light Microscope

Draw a large plan diagram of the region on P1 indicated by the shaded area in Fig. 2.1.

Use a sharp pencil.

Use one ruled label line and label to identify the xylem.

Observe the cells in the cortex of the organ on P1.

The cortex is the tissue beneath the outer layer of cells (epidermis) of the organ on P1.

Select a group of four adjacent cells from within this tissue, making sure that each of the four selected cells is touching at least two of the other cells.

• Make a large drawing of this group of four cells.
• Use one ruled label line and label to identify the cell wall of one of the cells that you have drawn.

Fig. 2.2 is a photomicrograph of a stained transverse section of the same organ shown on P1 from a different species of plant. This species of plant has thorns. One of the thorns has been labelled on Fig. 2.2.

Identify three observable differences, other than colour, size and presence or absence of thorns, between the section on P1 and the section shown in Fig. 2.2.

Record these three observable differences in an appropriate table.

The section through thorn Q is the shape of a triangle. Line R–S is the height of the triangle and line T–U is the width of the triangle.

• Measure the lengths of line R–S and line T–U on Fig. 2.3.

length of line R–S: ______

length of line T–U: ______

• Calculate the actual height and actual width of the section through thorn Q using your measurements for the lengths of line R–S (height) and line T–U (width).

Show your working.

actual height = ______

actual width = ______

Calculate the actual area of the section through thorn Q using your answers to (c)(i).

Show your working and give your answer to two significant figures.

actual area of section through thorn Q = ______

Draw a large plan diagram of a region of the organ on L1 to include the epidermis and two vascular bundles. Use a sharp pencil.

Use one ruled label line and label to identify the phloem.

Observe the xylem on the section of the plant organ on L1.

Select a line of four adjacent xylem vessel elements.

Each xylem vessel element must touch at least one of the other xylem vessel elements.

• Make a large drawing of this line of four xylem vessel elements.
• Use one ruled label line and label to identify the lumen.

Use Fig. 2.1 to calculate the actual length of one eyepiece graticule unit.

Show your working and give your answer in micrometres (µm).

$\text{actual length}$ = ______ $\text{µm}$

Fig. 2.2 is a photomicrograph of a stained transverse section of the same plant organ as the section on L1 but from a different plant.

This was taken using the same microscope and eyepiece graticule as in Fig. 2.1.

The eyepiece graticule scale has been placed across one of the larger sections of vascular tissue, labelled T in Fig. 2.2.

Use the calibration of the eyepiece graticule unit from (b)(i) to calculate the actual length of the section of vascular tissue T in Fig. 2.2.

Show your working and use appropriate units.

$\text{actual length of the vascular tissue T}$ = ______

Identify three observable differences, other than colour, between the section on L1 and the section in Fig. 2.3.

Record these three observable differences in Table 2.1.

Table 2.1

Identify the plant organ on L1 and in Fig. 2.3.

State how one observable feature helped you to identify the plant organ.

$\text{plant organ}$ = ______

Draw a large plan diagram of the leaf section on N1 shown by the shaded region in Fig. 2.1 (midrib).

Use a sharp pencil.

Use one ruled label line and label to identify the cuticle.

Observe the cells in the lower epidermis surrounding the midrib on the section of the leaf on N1.

Select a line of four adjacent lower epidermal cells.

• Make a large drawing of this line of four cells.
• Use one ruled label line and label to identify the cell wall of one cell.

Calculate the actual length of one eyepiece graticule unit shown in Fig. 2.2.

Give your answer in micrometres ($\mu\text{m}$).

Show your working.

actual length = ______ $\mu\text{m}$

Fig. 2.3 is a photomicrograph of a transverse section of a leaf from another plant of the same species as N1.

Fig. 2.3 was taken with the same microscope and the same lenses used to take the photomicrograph in Fig. 2.2.

Use the calibration of the eyepiece graticule unit from (b)(i) to calculate the actual width of the leaf in Fig. 2.3.

Show your working.

actual width = ______

Identify three observable differences, other than colour, between the leaf section on N1 and the leaf section in Fig. 2.3.

Record these three observable differences in Table 2.1.

Table 2.1

Draw a large plan diagram of the region of the leaf on M1 indicated by the shaded area in Fig. 2.1. Use a sharp pencil.

Use one ruled label line and label to identify the lower epidermis.

Observe the xylem vessel elements in the leaf on M1.

Select a line of four adjacent xylem vessel elements.

Each xylem vessel element must touch at least one other xylem vessel element.

• Make a large drawing of this line of four xylem vessel elements.
• Use one ruled label line and label to identify the wall of one xylem vessel element.

Fig. 2.2 shows a photomicrograph of a transverse section through a different leaf from that on M1.

Identify three observable differences, other than colour, between the section on M1 and the section in Fig. 2.2.

Record these three observable differences in Table 2.1.

Table 2.1

Fig. 2.3 is the same photomicrograph as that shown in Fig. 2.2.

Use the scale bar on Fig. 2.3 and the line D–E to calculate the actual length of the gap between the ends of the leaf.

Show your working, including units and give your answer in micrometres (µm).

actual length of gap = ______ $\text{µm}$

Draw a large plan diagram of the region on L1 indicated by the shaded area in Fig. 2.1.
Use a sharp pencil.

Use one ruled label line and label to identify one vascular bundle.

Observe the xylem vessel elements in the organ on L1.

Select a line of four adjacent xylem vessel elements.

Each xylem vessel element must touch at least one other xylem vessel element.

• Make a large drawing of this line of four xylem vessel elements.
• Use one ruled label line and label to identify the wall of one xylem vessel element.

Identify the plant organ on L1 and give a reason for your answer.

organ = ______

Fig. 2.2 is a photomicrograph of a stained transverse section of the same organ from a different plant to L1.

Identify two observable differences, other than colour, between the section on L1 and the section in Fig. 2.2.

Record these two observable differences in Table 2.1.

Table 2.1

Calculate the actual length of one eyepiece graticule unit shown in Fig. 2.3.

Give your answer in micrometres ($\mu\text{m}$).

Show your working.

actual length = ______ $\mu\text{m}$

Fig. 2.4 is the same photomicrograph as that shown in Fig. 2.2. This was taken with the same microscope and the same lenses used to take the photomicrograph in Fig. 2.3. The eyepiece graticule has been placed across the width of the tissue.

Use your calibration of one eyepiece graticule unit from (c)(i) to calculate the actual width of the tissue between the arrows on Fig. 2.4.

Show your working and use appropriate units.

actual width of the tissue between the arrows = ______

The width of the tissue in Fig. 2.4 varies. Suggest how you could more accurately calculate the width of the tissue.

Draw a large plan diagram of the whole section on N1. Use a sharp pencil.

Use one ruled label line and label to identify the phloem.

Observe the cortex on the section of the plant organ on N1. The cortex is the layer beneath the epidermis.

Select a group of four adjacent cortex cells.

Each cortex cell must touch at least two of the other cortex cells.

• Make a large drawing of this group of four cortex cells.
• Use one ruled label line and label to identify the cell wall of one cortex cell.

Fig. 2.1 is a photomicrograph of a stained transverse section of the same organ from a different plant to N1.

Fig. 2.1

Identify three observable differences, other than colour, between the section on N1 and the section in Fig. 2.1.

Record these three observable differences in Table 2.1.

Table 2.1

Determine the mean diameter of the section in Fig. 2.2.

Show your working and include units.

mean diameter = ______

Use the scale bar to calculate the mean actual diameter of the section in Fig. 2.2.

Show your working and include units.

mean actual diameter = ______

Use the mean actual diameter calculated in (c)(ii) to calculate the magnification of Fig. 2.2.

Show your working and give your answer to the nearest whole number.

magnification = ______

Draw a large plan diagram of the region on M1 indicated by the shaded area in Fig. 2.1.
Use a sharp pencil.

Use one ruled label line and label to identify the xylem.

Observe the xylem vessel elements in the stem on M1.

Select a group of four adjacent xylem vessel elements.

Each xylem vessel element must touch at least one other xylem vessel element.

• Make a large drawing of this group of four xylem vessel elements.
• Use one ruled label line and label to identify the wall of one xylem vessel element.

Fig. 2.2 is a photomicrograph of a stained transverse section of a stem from a different plant to M1.

Identify three observable differences, other than colour, between the stem section on M1 and the stem section in Fig. 2.2.

Record these three observable differences in an appropriate table.

Calculate the actual length of one eyepiece graticule unit shown in Fig. 2.3.

Give your answer in micrometres (µm).

Show your working and give your answer to three significant figures.

actual length of one eyepiece graticule unit = ______ $\text{µm}$

Fig. 2.4 is the same photomicrograph as that shown in Fig. 2.2. This was taken with the same microscope and the same lenses used to take the photomicrograph in Fig. 2.3.

The eyepiece graticule has been placed across the length of a vascular bundle.

Use the calibration of the eyepiece graticule unit from (c)(i) to calculate the actual length of the vascular bundle in Fig. 2.4.

Show your working and use appropriate units.

actual length of the vascular bundle = ______

Draw a large plan diagram of the whole section on N1. Use a sharp pencil.

Use one ruled label line and label to identify the phloem.

Observe the cortex on the section of the plant organ on N1. The cortex is the layer beneath the epidermis.

Select a group of four adjacent cortex cells.

Each cortex cell must touch at least two of the other cortex cells.

• Make a large drawing of this group of four cortex cells.
• Use one ruled label line and label to identify the cell wall of one cortex cell.

Fig. 2.1 is a photomicrograph of a stained transverse section of the same organ from a different plant to N1.

Identify three observable differences, other than colour, between the section on N1 and the section in Fig. 2.1.

Record these three observable differences in Table 2.1.

Table 2.1

Determine the mean diameter of the section in Fig. 2.2.

Show your working and include units.

mean diameter = ______

Use the scale bar to calculate the mean actual diameter of the section in Fig. 2.2.

Show your working and include units.

mean actual diameter = ______

Use the mean actual diameter calculated in (c)(ii) to calculate the magnification of Fig. 2.2.

Show your working and give your answer to the nearest whole number.

magnification = ______

Draw a large plan diagram of the region of the leaf on J1 indicated by the shaded area in Fig. 2.1.

Use a sharp pencil.

Use one ruled label line and label to identify the lower epidermis.

Observe the xylem vessel elements in the leaf on J1.

Select a line of four adjacent xylem vessel elements.

Each xylem vessel element must touch at least one other xylem vessel element.

• Make a large drawing of this line of four xylem vessel elements.
• Use one ruled label line and label to identify the wall of one xylem vessel element.

Identify three observable differences, other than colour, between the section on J1 and the section in Fig. 2.2.

Record these three observable differences in Table 2.1.

Table 2.1

Fig. 2.3 shows a diagram of a stage micrometer scale that is being used to calibrate an eyepiece graticule.

The length of one division on this stage micrometer is $0.2\ \text{mm}$.

Use Fig. 2.3 to calculate the length of one eyepiece graticule unit.

Show your working.

Include the unit in your answer.

length of one eyepiece graticule unit = ______

Fig. 2.4 shows the same eyepiece graticule and same lenses being used to measure the width of the section shown in Fig. 2.2.

Use your answer in (b)(ii) to calculate the actual width of the section shown in Fig. 2.4.

Show your working.

actual width of the section = ______

Draw a large plan diagram of the region of the root on K1 indicated by the shaded region in Fig. 2.1. Use a sharp pencil.

Use one ruled label line and label to identify the endodermis.

Observe the xylem vessel elements in the root on K1.

Select a group of four adjacent xylem vessel elements.

Each xylem vessel element must touch at least two other xylem vessel elements.

• Make a large drawing of this group of four xylem vessel elements.
• Use one ruled label line and label to identify the cell wall of one xylem vessel element.

Identify three observable differences, other than colour, between the root section on K1 and the root section in Fig. 2.2.

Record these observable differences in Table 2.1.

Table 2.1

Line A–B represents the diameter of the root in Fig. 2.2.

Use the scale bar on Fig. 2.2 to calculate the actual diameter of the root.

Show your working.

Include the unit in your answer.

actual diameter = ______

Use your value from (b)(ii) to calculate the magnification of Fig. 2.2.

Give your answer to two significant figures.

magnification = $\times$ ______