The leaf as an organ

Organisation · Plant tissues, organs and systems · note 2 of 5

Spec 4.2.3.1Download these notes (PDF)6 pages

The leaf as an organSpec 4.2.3.1

The leaf is a plant organ. It is made up of several tissues that work together. Knowledge is limited to the epidermis, palisade and spongy mesophyll, xylem and phloem, and guard cells surrounding stomata.

The epidermis covers the leaf. The lower epidermis contains stomata.
Palisade mesophyll lies below the upper epidermis. It is where most photosynthesis happens.
Spongy mesophyll lies below the palisade layer. Its air spaces let gases move around.
Xylem and phloem in the leaf veins bring water to the leaf and take sugars away.
Guard cells surround each stomatal pore and control its opening.

A transverse section of a leaf labelled with the waxy layer, upper epidermis, palisade mesophyll, spongy mesophyll, air space, xylem and phloem in a vein, lower epidermis, a stoma and a guard cell. — The tissues of a leaf work together. Most photosynthesis happens in the palisade mesophyll.