The conversion of light energy, water and carbon dioxide in the presence of chlorophyll to carbohydrates, with oxygen being released as a by-product. Some leaves are sessile , lacking a petiole. At the base of every leaf, there is always an axillary bud. Some leaves are identified by their characteristic leaf margin, the edge of the leaf. A leaf with several blades or leaflets is a compound leaf .
Leaves can have different arrangements on a stem.
Plants with alternate leaves have one leaf at each node. Plants with an opposite leaf arrangement have two leaves per node Plants with whorled leaves have three or more leaves per node. The arrangement of veins within a leaf is characteristic of different types of plants. Monocots, like corn or grass, always have all of their veins arranged in a parallel fashion. Dicots, like oak or maple trees, have what is termed netted venation .