Leaves
Leaves
 
When you have finished this page,        try the Leaves Quiz.
The leaf is a part of the plant        that is charge of making food for the plant. This food making process is        called photosynthesis.
Parts of the leaf
The leaf consists of the following        parts:
Petiole - a thin stalk that connects        the blad of the leaf to the plant's stem. These veins are called
Blade - a thin, flat part of        the leaf that extends off the end of the petiole. It is green as it contains        cholorophyll which is necessary in making the plant's food..
The blade contains veins which        help bring in the water necessary for photosynthesis and to transport food        out to all parts of the plant. The xylem is responsible for water transportation        and the phloem for food.
The blade also has several layers.        The top layer is covered with a waterproof coat called the cuticle. Both        the upper and lower layer contain paired cells called guard cells. These        guard cells manage the stomata, little openings in the leaf that allow for        the taking in of carbon dioxide and the emission of oxygen during photosynthesis.        Water vapor is also emitted in a process called transpiration.
In between the top and bottom        layers of the blade are cells that are full of chlorophyll that is essential        for the plant to make its food during photosynthesis.
Leaves come in a variety of shapes,        sizes, color, and textures. Leaves can be grouped as simple with one blade        or compound with many leaflets. The edges of leaves can be smooth, have        jagged edges referred to as toothed or scalloped edges referred to as lobed        edges. Leaves can also be divided into how their veins are arranged. The        leaves of plants referred to as monocots have leaves that run parallel to        each other off one central vein. Those that are referred to as dicots have        leaves with veins that branch out two different ways.Pinnate have one main        vein called the midrib, and smaller branching veins. Palmates have several        large veins branching from the leaf base into the blade.
Some leaves have special            features such as spines and bud scales to protect them. Some are climbing            (tendrils). Others catch insects. Some store water. These are called            succulents or store food such as bulb scales.
Leaves contain other substances            besides chlorophyll that give the leaf color. These substances are called            pigments and cause leaves to turn colors in autumn. These leaves are            on deciduous trees and fall off and die. New ones grow back in the spring.            Conifers or trees that bear cones can keep their needles for years and            grow new ones as soon as they lose them.