Leaf
Leaf
Leaf, part of a plant that serves primarily as the plant's food-making organ in a process called photosynthesis. Leaves take part in other plant functions as well, including transpiration and guttation, both of which remove excess water from the plant, and respiration, the process by which a plant obtains oxygen and energy. Leaves also may store food and water and provide structural support.
A leaf is an extension of a plant's stem. Although most leaves are flat, broad, or bladelike, they also may be many other shapes, including round, oval, or feathery. In general, the leaves of trees such as hardwoods tend to be broad and relatively large, and the leaves of conifers, or cone-bearing trees, are usually small and needlelike in shape. In size, leaves range from only several millimeters (a fraction of an inch) long, as in the water plant Elodea, to 15 to 18 m (15 to 60 ft) long, as in some palm trees.
Green leaves derive their color from a green pigment called chlorophyll. The presence of additional pigments causes other leaf colors such as red in coleus and purple in cabbage. In temperate regions of the world, the leaves of some plants change color in autumn. Leaves of most garden plants turn yellow in the autumn, but those of many trees take on brilliant orange or red colors.
See Parts of Typical Leaf; Importance of Leaf.
Leaf, part of a plant that serves primarily as the plant's food-making organ in a process called photosynthesis. Leaves take part in other plant functions as well, including transpiration and guttation, both of which remove excess water from the plant, and respiration, the process by which a plant obtains oxygen and energy. Leaves also may store food and water and provide structural support.
A leaf is an extension of a plant's stem. Although most leaves are flat, broad, or bladelike, they also may be many other shapes, including round, oval, or feathery. In general, the leaves of trees such as hardwoods tend to be broad and relatively large, and the leaves of conifers, or cone-bearing trees, are usually small and needlelike in shape. In size, leaves range from only several millimeters (a fraction of an inch) long, as in the water plant Elodea, to 15 to 18 m (15 to 60 ft) long, as in some palm trees.
Green leaves derive their color from a green pigment called chlorophyll. The presence of additional pigments causes other leaf colors such as red in coleus and purple in cabbage. In temperate regions of the world, the leaves of some plants change color in autumn. Leaves of most garden plants turn yellow in the autumn, but those of many trees take on brilliant orange or red colors.
See Parts of Typical Leaf; Importance of Leaf.
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