Page 94 - PG 101-Course notes مذكرة النظري 24-25 with spec

Medicinal plants (PG 101) Level 1 Clinical Pharmacy-PharmD

1-The epidermis

• Is found as a single layer on both the upper and lower surfaces.

• Chlorophyll and intercellular spaces are absent.

• Trichomes and stomata are present on either sides or one of them, stomata are

more frequent on the lower epidermis.

2-The ground tissue

 It is known as mesophyll which is usually specialized as a photosynthetic tissue.

• In Dicots, it is divided into palisade and spongy parenchyma.

a- Palisade tissue consists of one or more layers of elongated cells

below the epidermis and perpendicular to it.

- The palisade cells contain abundant chloroplasts and have

narrow intercellular spaces between them.

- Palisade may be present on one surface only (dorsiventral

leaves) or on both surfaces (isobilateral leaves).

a- Spongy tissue consists of irregular shaped cells, have large

intercellular spaces.

- The cells contain less chloroplasts than the palisade cells, so

they are less specialized as photosynthetic tissue

• In monocots, the mesophyll cells are all alike i.e., not differentiated into

palisade and spongy cells.

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