Emma asked in Science & MathematicsBotany · 1 decade ago

What are leaves?

Update:

what are the leaves made of like from the inside.

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  • 1 decade ago
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    In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat (laminar) and thin, to expose the cells containing chloroplast (chlorenchyma tissue, a type of parenchyma) to light over a broad area, and to allow light to penetrate fully into the tissues. Leaves are also the sites in most plants where respiration, transpiration, and guttation take place. Leaves can store food and water, and are modified in some plants for other purposes. The comparable structures of ferns are correctly referred to as fronds. Leaves are prominent in the human diet as leaf vegetables.

    Leaf anatomy

    A structurally complete leaf of an angiosperm consists of a petiole (leaf stem), a lamina (leaf blade), and stipules (small processes located to either side of the base of the petiole). The point at which the petiole attaches to the stem is called the leaf axil. Not every species produces leaves with all of these structural parts. In some species, paired stipules are not obvious or are absent altogether. A petiole may be absent, or the blade may not be laminar (flattened). The tremendous variety shown in leaf structure (anatomy) from species to species is presented in detail below under Leaf morphology.

    A leaf is considered to be a plant organ, typically consisting of the following tissues:

    1. An epidermis that covers the upper and lower surfaces

    2. An interior chlorenchyma called the mesophyll

    3. An arrangement of veins (the vascular tissue).

    Epidermis

    The epidermis is the outer multi-layered group of cells covering the leaf. It forms the boundary between the plant and the external world. The epidermis serves several functions: protection against water loss, regulation of gas exchange, secretion of metabolic compounds, and (in some species) absorption of water. Most leaves show dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions.

    The epidermis is usually transparent (epidermal cells lack chloroplasts) and coated on the outer side with a waxy cuticle that prevents water loss. The cuticle may be thinner on the lower epidermis than on the upper epidermis, and is thicker on leaves from dry climates as compared with those from wet climates.

    The epidermis tissue includes several differentiated cell types: epidermal cells, guard cells, subsidiary cells, and epidermal hairs (trichomes). The epidermal cells are the most numerous, largest, and least specialized. These are typically more elongated in the leaves of monocots than in those of dicots.

    The epidermis is covered with pores called stomata, part of a stoma complex consisting of a pore surrounded on each side by chloroplast-containing guard cells, and two to four subsidiary cells that lack chloroplasts. The stoma complex regulates the exchange of gases and water vapor between the outside air and the interior of the leaf. Typically, the stomata are more numerous over the abaxial (lower) epidermis than the adaxial (upper) epidermis.

    Veins

    The veins are the vascular tissue of the leaf and are located in the spongy layer of the mesophyll. They are typical examples of pattern formation through ramification.

    The veins are made up of:

    - xylem, which brings water from the roots into the leaf.

    - phloem, which usually moves sap out, the latter containing the glucose produced by photosynthesis in the leaf.

    The xylem typically lies over the phloem. Both are embedded in a dense parenchyma tissue, called "pith", with usually some structural collenchyma tissue present.

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  • 1 decade ago

    In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat (laminar) and thin, to expose the cells containing chloroplast (chlorenchyma tissue, a type of parenchyma) to light over a broad area, and to allow light to penetrate fully into the tissues. Leaves are also the sites in most plants where respiration, transpiration, and guttation take place. Leaves can store food and water, and are modified in some plants for other purposes. The comparable structures of ferns are correctly referred to as fronds. Leaves are prominent in the human diet as leaf vegetables.

  • Mrs. T
    Lv 4
    1 decade ago

    Tree hair

  • Anonymous
    1 decade ago

    God's miracle workers.

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  • 1 decade ago

    shelter for the birds.

  • 1 decade ago

    catzpaw is correct

  • 5 years ago

    your actually retarded

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