3.4.4: Chapter Summary

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Melissa Ha, Maria Morrow, & Kammy Algiers
Yuba College, College of the Redwoods, & Ventura College via ASCCC Open Educational Resources Initiative

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Leaves are the main site of photosynthesis. A typical leaf consists of a blade (the broad part of the leaf, also called the lamina) and a petiole (the stalk that attaches the leaf to a stem). The arrangement of leaves on a stem, known as phyllotaxy, enables maximum exposure to sunlight. Each plant species has a characteristic leaf arrangement and form. The pattern of leaf arrangement may be alternate, opposite, or whorled, while leaf form may be simple or compound (consisting of multiple leaflets). Leaves also differ in the venation patterns, margins (edges), and shape.

Leaf tissue consists of the epidermis, which forms the outermost cell layer, and mesophyll and vascular bundles (veins), which make up the inner portion of the leaf. Leaves may be mesophytic (adapted to moderate water availability), hydrophytic (adapted to on water), or xerophytic (adapted for dry conditions). Pine leaves share some characteristics with other xerophytic leaves. The leaves of corn, a monocot, are characterized by Kranz anatomy, parallel vascular bundles, and bulliform cells. Leaves that develop in the sun tend to be thicker, have a thicker cuticle, and have more palisade mesphyll than those that develop in the shade.

In some plant species, leaf form is modified for functions other than photosynthesis, form structures such as tendrils, spines, or bracts.

After completing this chapter, you should be able to...

Identify the main parts of a leaf.
Compare petiolate and sessile leaves.
Distinguish among alternate, opposite, and whorled phyllotaxes.
Compare simple, pinnately compound, and palmately compound leaves.
Compare parallel, pinnate, and palmate venation in leaves.
Recognize common leaf margins and shapes.
Describe the microscope internal structure of leaves, including the epidermis, mesophyll, and vascular bundles.
Compare the adaptations of mesophytic, hydrophytic, and xerophytic leaves.
Identify the unique features of pine and corn leaves.
Compare the structures of sun and shade leaves.
Identify common leaf modifications and their functions, including storage leaves, succulent leaves, spines, tendrils, phyllodes, showy bracts, plantlets, and insect traps.

Attribution

Curated and authored by Melissa Ha using 30.4 Leaves from Biology 2e by OpenStax (licensed CC-BY). Access for free at openstax.org.