Mesophyll
/ˈmɛsəˌfɪl/
Definition
Mesophyll is the inner tissue of a leaf, located between the upper and lower epidermis. It consists mainly of photosynthetic cells with chloroplasts, where much of photosynthesis takes place. In many leaves, it is divided into palisade mesophyll, with tightly packed cells that capture light, and spongy mesophyll, with air spaces that help gas exchange. This distinguishes it from the outer protective epidermis and the leaf veins.
Function in Plants
- Photosynthesis site: mesophyll contains most of the chloroplasts in a leaf, so it is where much of the plant’s sugar production from light takes place.
- Gas exchange pathway: Air spaces between cells help carbon dioxide move to photosynthetic cells and allow oxygen and water vapor to diffuse back out through the stomata.
- Layer differences: In many broad leaves, the upper palisade region captures light efficiently, while the lower spongy region promotes internal air movement and gas exchange.
- Link to leaf performance: Its structure influences how a leaf balances light capture, water loss, and cooling, which affects growth rate and tolerance of sun or shade conditions.
Related Terms
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Vein
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