Leaves

Leaves are organs found in the shoot system of all vascular plants. Although their form and the existence of secondary functions vary, they are primarily developed so that the plant can perform optimal photosynthesis. Leaves are made from a blade that maximizes the surface area of sunlight absorbed and veins which transport nutrients and water through vascular tissue.

A typical leaf consists of the leaf blade and the petiole. It attaches to the stem at a node. This attachment forms an axil and creates the opportunity for axillary buds to grow. Leaves grow in standardized patterns when no mutation occurs. They may be present in simple, compound, or intermediate patterns; they may be pinnately or palmately attached to a single node; and they may be alternating, opposite, or whorled leaves.

Leaves are a modifiable organ. For example, when present in the reproductive region of an angiosperm, they make up the petals and sepals of the flower, and their structure is modified into a pistil carpel. They may be modified for additional functions in herbaceous bulbs and as the bracts of angiosperms and gymnosperms. Other examples include some plant tendrils and the defensive spines of cacti.

Most leaves grow indeterminately alongside the plant unless they are modified for a specific purpose. In sympodial plants, the flower grows on the terminal of the shoot using the leaf primordia, which prevents the growth of further leaves on that stem.