Midrib
/ˈmɪdˌrɪb/
Definition
Midrib refers to the main central vein of a leaf blade. It runs from the leaf stalk, or petiole, toward the tip and is usually thicker and more prominent than the smaller side veins branching from it. The midrib contains vascular tissue, which carries water, minerals, and sugars, and it also helps support the leaf’s shape. In many leaves, it is visible as the raised line on the underside.
Function in Plants
- Support for the blade: The midrib helps hold the leaf blade in shape, which can keep the surface spread for light capture and reduce tearing or folding in wind and rain.
- Main route for transport: It contains major vascular tissue, the xylem and phloem, which move water, minerals, and sugars between the leaf blade and the rest of the plant.
- Useful ID feature: Its thickness, color, prominence, and whether it is raised or recessed are often used in plant identification, especially when comparing similar leaves.
- Clue to leaf condition: Damage, browning, or collapse along the midrib can affect the whole leaf because this central area supports both structure and internal transport.
Related Terms
Vein
Vein refers to one of the vascular strands in a leaf or other plant organ. It contains xylem and phloem, the tissues…
Leaf
Leaf refers to a plant organ, usually flat and green, that grows from the stem or a branch and is specialized for…
Leaf blade
Leaf blade refers to the broad, usually flat part of a leaf, also called the lamina. It is the main photosynthetic…
Petiole
Petiole refers to the stalk that attaches a leaf blade to the stem. It is a plant structure found in many, but not all…
Venation
Venation refers to the pattern and arrangement of veins in a leaf blade, or sometimes in other flat plant organs. It is…
Palisade mesophyll
Palisade mesophyll is a layer of tightly packed, elongated cells inside a leaf, usually just beneath the upper…
Mesophyll
Mesophyll is the inner tissue of a leaf, located between the upper and lower epidermis. It consists mainly of…