Leaf
/lif/
Definition
Leaf refers to a plant organ, usually flat and green, that grows from the stem or a branch and is specialized for photosynthesis, the process that uses light to make sugars. Most leaves have a blade and often a stalk called a petiole, with veins that transport water and nutrients. Unlike stems, leaves are typically determinate, meaning they stop growing after reaching a set form.
Function in Plants
- Photosynthesis site: A leaf is the main place where most plants capture light and turn carbon dioxide and water into sugars through photosynthesis, supplying energy for growth, flowering, and fruiting.
- Gas exchange control: Tiny pores called stomata, often concentrated on the surface, let a leaf take in carbon dioxide and release oxygen and water vapor. Their opening and closing helps balance photosynthesis with water loss.
- Cooling and water movement: Water evaporating from a leaf helps cool the plant and supports transpiration, the upward flow of water and dissolved minerals from the roots through the vascular system.
- Key identification feature: Shape, vein pattern, margin, texture, and arrangement are major traits used to identify plant species and cultivars, especially when flowers or fruits are absent.
Related Terms
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…
Midrib
Midrib refers to the main central vein of a leaf blade. It runs from the leaf stalk, or petiole, toward the tip and is…
Vein
Vein refers to one of the vascular strands in a leaf or other plant organ. It contains xylem and phloem, the tissues…
Venation
Venation refers to the pattern and arrangement of veins in a leaf blade, or sometimes in other flat plant organs. It is…
Leaf axil
Leaf axil refers to the upper angle formed where a leaf stalk or leaf base joins the stem. It is a plant structure and…