Pearson International A Level Biology Core Practical 7: Observe and draw plant tissue sections and cells

This guide practises observing and drawing plant tissue sections and cells. It is not a complete sectioning or staining protocol, or a claim to reproduce Pearson's prescribed procedure. Use suitable prepared slides or a named preparation method approved by your centre, with the current course documents and risk assessment.

Aim and scientific principle

Observe a named plant organ and section orientation, record the arrangement of tissue regions, and draw cell detail actually resolved. Define any dimension being measured and keep the tissue plan distinct from the higher-power cell drawing.

State the observation or comparison required. Descriptive tissue observation need not have a manipulated independent variable. If comparing organs, species or treatments, define that comparison and the sampling unit, and keep the relevant preparation, section orientation and measurement conditions comparable.

Apparatus and setup

Use a light microscope, suitable prepared plant sections or approved mounting equipment, and the tools and stain required by the selected preparation. Use an eyepiece graticule with a stage micrometer when calibrated microscopic dimensions are needed. A ruler measures a drawing on paper, not the microscopic specimen directly. Consider measuring range, resolution, uncertainty, calibration and suitability for the sample, not the instrument name alone. Draw a labelled scientific setup that shows the working geometry and exactly where readings are taken. Include a control or blank when it distinguishes the target effect from drift, contamination or background response.

Check focus, illumination and whether the intended tissue boundaries or cell features can be resolved. If measuring dimensions, calibrate for the actual objective, eyepiece and optical configuration, and record reading uncertainty. Scale spacing, image magnification and optical resolving power are distinct properties.

Method

1. Record the plant species or supplied identity, organ, sampled region, developmental context where known, and section orientation. Select a suitable prepared section or follow the named approved preparation. Add stain, mounting liquid or a coverslip only when required; do not add liquid to an already sealed slide.
2. For a wet mount, lower the coverslip at an angle to reduce bubbles and remove excess liquid as prescribed. Avoid unnecessary pressure or squashing that would distort tissue organisation.
3. Begin at low power to locate tissue regions and record a plan of their observed relative positions and proportions. Mark the region selected for a separate higher-power cell-detail drawing. Use fine focus at higher power and avoid contact between the objective and slide.