Dicotyledonous Stem Structure
Distribution of tissues in a transverse section of a dicotyledonous stem
- The stem in a dicotyledonous plant contains several different types of tissues, which include:
- The epidermis which forms the outer layer of the stem
- This prevents water loss and provides protection from herbivores
- Parenchyma which forms the cortex and pith of the stem
- These cells act as storage structures for starch and other substances
- The cortex is the region located directly beneath the epidermis while the pith is the central region of the stem
- Vascular tissue arranged in a ring of vascular bundles
- Xylem transports water and dissolved mineral ions from the roots to the leaves
- Phloem transports organic solutes from the leaves to other parts of the plant
- The epidermis which forms the outer layer of the stem
- The distribution of tissues in a transverse section of a dicotyledonous stem can be represented as a plan diagram
- There are a few things to keep in mind when drawing plan diagrams:
- Do not draw individual cells; only the outline of different tissues are drawn
- Draw clear, continuous lines; do not sketch
- Avoid shading parts of your drawing
- Pay attention to the size and proportions of different parts visible in a micrograph
- Make sure the different parts are clearly labelled
- Add a scale bar or the estimated size of your drawing
- Include annotations that give the functions of the labelled sections
A plan diagram (bottom right) showing the distribution of different tissues in a dicotyledonous stem
Note that a hand-drawn plan diagram should not contain shading
Examiner Tip
You are expected to annotate your drawing with the main functions of these structures; this is not shown above