Page 42 - PRE-U STPM BIOLOGY TERM 1

Biology Term 1 STPM Chapter 2 Structure of Cells and Organelles

4. The functions of parenchyma are as follows:
(a) It functions as a photosynthetic tissue as in the mesophyll of the
leaves or in young stems.
(b) It functions as a storage tissue as in the cortices or the pith of
stems and roots. Some fruits and seeds have parenchyma cells as
storage tissue.
(c) It functions as packing tissue around the vascular bundles of 2
stems and leaf stalks.
(d) As epidermis, it protects the cells beneath physically and from
desiccation.
Collenchyma

1. Collenchyma is a tissue where the cells have thickened non-uniform
primary cell walls.

2. The structure of collenchyma are as follows:
(a) The cells are alive with protoplast and nucleus.
(b) The shape of the cells is isodiametric or like an elongated prism.
(c) The cell wall is not uniformly thickened. The collenchyma
is divided into two types: angular (thickened at corners) and
lamella (thickened at tangential wall) types.

Figure 2.34 Collenchyma

(d) The cell wall is of primary type and not lignified.
(e) The cells are compact with no intercellular space.
3. Its distributions are shown in Figures 2.26 and 2.32.
(a) It is found below the epidermis of dicotyledonous stems.
(b) It is found beneath the epidermis of the main vein of
dicotyledonous leaves.
4. The functions of collenchyma are listed as follows:
(a) It functions to support the stem or the leaves of dicotyledonous
plants.
(b) It becomes meristematic and produces cork cambium in the
dicotyledonous stem that undergoes secondary thickening.

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