Vascular plants transport sucrose in a special tissue called the phloem. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the plant shoots and roots.

The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf ( epidermis), while leaves are orientated to maximize their exposure to sunlight. The sugars are then stored as starch, further processed by chemical synthesis into more complex organic molecules such as proteins or cellulose, the basic structural material in plant cell walls, or metabolized by cellular respiration to provide chemical energy to run cellular processes. They capture the energy in sunlight and use it to make simple sugars, such as glucose and sucrose, from carbon dioxide and water. Green plants are autotrophic, meaning that they do not obtain food from other living things but instead create their own food by photosynthesis. Leaves are the most important organs of most vascular plants. Examples include the phyllids of mosses and liverworts.ģD rendering of a computed tomography scan of a leaf Some structures of non-vascular plants look and function much like leaves. Examples include flattened plant stems called phylloclades and cladodes, and flattened leaf stems called phyllodes which differ from leaves both in their structure and origin. Furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. In many aquatic species, the leaves are submerged in water.

Some leaves, such as bulb scales, are not above ground.

In the lycopods, with different evolutionary origins, the leaves are simple (with only a single vein) and are known as microphylls. The broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants, which also includes acrogymnosperms and ferns. Leaves can have many different shapes, sizes, and textures. A leaf with lighter-colored or white patches or edges is called a variegated leaf. Leaves are mostly green in color due to the presence of a compound called chlorophyll that is essential for photosynthesis as it absorbs light energy from the sun. Most leaves are flattened and have distinct upper ( adaxial) and lower ( abaxial) surfaces that differ in color, hairiness, the number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax and other features. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Leaves are collectively called foliage, as in 'autumn foliage', while the leaves, stem, flower, and fruit collectively form the shoot system. A leaf ( PL: leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis.

I am a leaf on the wind origin