R2101 Feb ‘18
Q4a) Draw and fully label a diagram to show the internal structure of a dicotyledonous leaf in the space below. 8 marks
b) State TWO differences between dicotyledonous and monocotyledonous leaves. 2 marks
Part a) is an example of a question requiring a diagram. Diagrams do not need to be wonderful works of art for exams, but do need to be very clear and recognisable. You need to label carefully to show exactly which part the label is indicating. It is worth practising drawing diagrams for all the parts of the syllabus that include them.
The part of the syllabus that this relates to is:
2.5 Describe the structure and state the function of leaves.
Draw a dicotyledon leaf section to show the following components epidermis, xylem, phloem, veins, palisade and spongy mesophyll, cuticle, guard cells and stomata.
The question asks for the internal structure, so it is clear that a leaf section is required as in the syllabus, rather than a diagram of the outside of the leaf.
There are eight components in the syllabus or nine if you label palisade mesophyll and spongy mesophyll separately.
The examiner’s comments state that ‘the best candidates drew the internal structure of the leaf which showed eight recognisable features, in the correct position, accurately labelled and spelt. These included: epidermis, cuticle, palisade mesophyll, spongy mesophyll, air spaces, guard cells and stomata, chloroplast, xylem and phloem and vein/midrib’.
leaf example diagram
Part b) needs two straightforward statements. It refers to the following part of the syllabus:
1.1 Describe plant groups of significance to horticulture.
Describe the differences between monocotyledons and dicotyledons: features of root, stem, leaf, flower and seed including internal arrangements of vascular bundles in stems and roots.
For a question that asks for differences between it is important to state both parts clearly, and to make sure that both parts are related. The examiner’s comments suggest the following as suitable:
- Dicotyledonous leaves have a variety of shapes whereas monocotyledonous leaves are strap-like.
- Dicotyledonous leaves have reticulate or branching veins whereas monocotyledonous leaves have parallel veins.
- Dicotyledonous leaves have their stomata mainly in the lower epidermis whereas monocotyledonous leaves have their stomata equally distributed on the upper and lower leaf surface.