Leaf (Encyclopedia of Science)
A leaf is a plant's principal organ of photosynthesis, the process by which sunlight is used to form foods from carbon dioxide and water. Leaves also help in the process of transpiration, or the loss of water vapor from a plant.
A typical leaf is an outgrowth of a stem and has two main parts: the blade (flattened portion) and the petiole (pronounced PET-ee-ole; the stalk connecting the blade to the stem). Some leaves also have stipules, small
paired outgrowths at the base of the petiole. Scientists are not quite sure of the function of stipules.
Leaf size and shape differ widely among different species of plants. Duckweeds are tiny aquatic plants with leaves that are less than 0.04 inch (1 millimeter) in diameter, the smallest of any plant species. Certain species of palm trees have the largest known leaves, more than 230 feet (70 meters) in length.
(The entire section is 1097 words.)
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