Page 83 - Biology Form Two

Biology for Secondary Schools

together with their associated fibres to all parts of the plant. The phloem
are collectively known as vascular tissue is responsible for transporting
bundles. The xylem tissue has the role manufactured food from the sites of
of transporting water and mineral salts photosynthesis to all parts of the plant.
absorbed from the soil through roots
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Xylem

Phloem Vascular

Vascular cambium bundle

(a) Dicot stem (b) Monocot stem

Figure 4.1: Vascular bundle in the stem

Xylem
Xylem is one of the conducting tissues in plants, which primarily transports water
and dissolved minerals from roots to stem and leaves. It also provides mechanical

strength to the plants. It mostly occurs in the inner part of the vascular bundles.
The movement of substances in the xylem of the main stem is always upward.
Xylem is a complex tissue composed of four different kinds of cells which are
xylem vessel elements, tracheids, fibres, and parenchyma cells. Figure 4.2 shows
the structure of the xylem tissue.

Xylem fibres Pits

Xylem vessel
element

Xylem parenchyma cell

Tracheids
Figure 4.2: Structure of the xylem

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