Page 123 - General and Inorganic Chemistry for Advanced Secondary Schools Students Book Form Five and Six

Biology for Secondary Schools

Internal structure of a leaf grows, the leaf can either have stomata
on both sides on one side (lower or
Task 6.2
upper part). But in most plants, the
Search from library and reliable internet lower epidermis has more stomata
sources the information on internal than the upper epidermis. Immediately
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structures of a leaf that are related to below the epidermis is another
photosynthesis.
tissue layer called mesophyll, that is
photosynthetic because it contains
The internal features of a leaf can be chloroplasts.
viewed under a microscope. Figure 6.2
shows the internal structure of a leaf.
The leaf has lower and upper parts The mesophyll tissue is divided into two
which are covered by a thin waxy layer parts, namely the palisade and spongy
called cuticle. On the upper part of the mesophyll. The palisade mesophyll
leaf is the upper epidermis while the cells are usually tightly packed. The
lower epidermis is located on the lower spongy mesophyll has loosely packed
part of the leaf.
cells. It also consists of air spaces and

The leaf has small openings called vascular tissues which are made up of
stomata. Depending on the species of xylem and phloem cells, as shown in
a plant and the environment in which it Figure 6.2.

Upper epidermis Cuticle

Palisade mesophyll

Mesophyll
Spongy mesophyll

Xylem
Air spaces
Phloem
Lower epidermis
Cuticle

Stomata
Figure 6.2: Internal structure of a leaf

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