Drawing Root & Stem Structure: Skills (DP IB Biology)
Revision Note
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 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 Tips and Tricks
You are expected to annotate your drawing with the main functions of these structures; this is not shown above
Dicotyledonous Root Structure
Distribution of tissues in a transverse section of a dicotyledonous root
The arrangement of the vascular tissues differ in a root compared to a stem
The xylem is centrally located in a root in a cross-shaped structure, while it forms the outer part of the ring of vascular bundles in a stem
Remember, x = a cross = xylem
Phloem bundles are arranged between the cross "arms" of xylem in a root, while it forms the inner part of the ring of vascular bundles in a stem
The cortex consists of parenchyma cells that store starch and other substances while the epidermis forms the outer layer of the root
Specialised epidermal cells called root hairs are present in roots to absorb water and mineral ions from the soil
The endodermis forms the boundary between the vascular tissue and cortex in a root
You should be able to draw a plan diagram of the tissues in a dicotyledonous root; see above for the features of a plan diagram drawing
A plan diagram (bottom right) of a dicotyledonous root showing the distribution of different tissues
Note that hand-drawn plan diagrams should not contain any shading
Examiner Tips and Tricks
Don't forget to draw your plan diagrams large enough to fill at least half of the available space on a page. Making a drawing that is too small will make it difficult to label structures accurately and may cost you marks
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