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| Complex Tissues |
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| Complex tissues are made up of more than one type of cells and they work together as a unit. They transport water, salt and prepared food material to various parts of the plant body. Complex tissues are of two types. |
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 Xylem |
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 Phloem (bast) |
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| Xylem and Phloem are also called vascular tissue and together they constitute vascular bundles. |
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| Xylem or wood is a conducting tissue and is composed of elements of different kinds. They are: |
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 Tracheids |
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 Vessels or tracheae |
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 Xylem parenchyma |
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 Xylem sclerenchyma |
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| Nature |
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 Tracheids |
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| These are elongated cells with sloping walls enclosing a large empty cavity. Cell walls are thickened with lignin. The cells are dead. |
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 Vessels or trachea |
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| These are cylindrical tube-like structures formed by a row of cells placed end to end. The transverse walls between the cells are almost dissolved forming a continuous channel or water-pipe. The cells are dead. |
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 Xylem parenchyma |
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| These are made up of parenchymatous cells. They are thin walled and are living. |
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 Xylem sclerenchyma |
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| These are sclerenchymatous cells and form the wood in older plants. The cells are dead. |
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| Occurrence |
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| Found in the root, stem and leaves. They occur along with phloem to form the vascular bundle. |
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| Function: |
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 Conduct water and minerals upwards from the roots to the stem and leaves. |
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 Cells that are lignified to give mechanical strength to the plant. |
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| Tracheids with scalariform pits |
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| Phloem or bast is also a conducting tissue and is composed of elements of different kinds. |
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| Elements of phloem |
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| Nature |
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 Sieve Tubes |
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| The cell walls are thin and the cells elongated, placed end-to-end forming a slender tubular structure. Transverse walls are perforated forming a sieve plate. Cytoplasm of one sieve element is continuous with those of the sieve elements above and below by cytoplasmic connections passing through the pores of the sieve plate. |
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 Companion cells |
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| Associated with the sieve tube is a small cell containing dense cytoplasm and a large elongated nucleus. |
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 Phloem Parenchyma |
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| These are ordinary parenchymatous cells and are living. They are absent in monocot stems. |
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 Bast Fibres |
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| These are sclerenchymatous cells. The cells are dead. |
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| Occurrence |
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| Phloem is found in all parts of the plantlike roots, stem and leaves. They occur together with the xylem to form the vascular bundle. |
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| Function |
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| The function of the phloem is to conduct prepared food from the leaves to the growing parts of the plant and the storage organs. |
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| Sieve-tube in transection |
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| In a nutshell Xylem and Phloem can be summarized like this: |
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