Tag Archives: Compound Leaf

Parts of a Leaf: A Diagram

Maple leaf (Acer sp.)

Maple leaf (Acer sp.)

Leaf‘ – used to describe the combination of the petiole and blade(s).

Blade – usually broad and flat.  This blade the main ‘engine’ of the plant, where most of the chlorophyll in a plant is. They can also be described as the lungs of plant since this is where the exchange of the carbon dioxide and oxygen occur on a plant. Simple leaves have one blade. In compound leaves there are multiple blades attached to one petiole, with each blade refered to as a leaflet.

Petiole –  many times described as the ‘stem’ of the leaf. Not to be confused with the actual stem of the plant, the petiole is not a woody structure and will fall with the rest of the leaf at the beginning of the plant’s dormant season. If you think you are looking at a compound leaf and are unsure of where the petiole is an easy way to find where the petiole of the leaf is to backtrack from the leaf blade until you reach a bud. The piece before you hit the bud is the petiole. On compound leaves the petiole-like structure between the individual leaflets is a rachis.

Vein – visually appears to us like the ribs of the leaf with the central vein often called the midrib. If you can’t distinguish where the veins are turn the leaf over as they are often more pronounced on the backside of the leaf. Internally the vein is a bundle of vascular tissue that acts as a tunnel for water, sugars, and nutrients to move in and out of the leaf.

Margin – the outer edge of the leaf blade. Different margins include entire (smooth), serrated and toothed (like a saw blade), doubley serrated (little teeth on top of the big teeth), undulated (wavy), and lobed (thick finger-like projections).

Tip – the tip of the leaf.

Base – the base of the leaf.