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Transcript
Cell types Collenchyma Collenchyma cells are characterized by having thickened primary cell walls. They function for structural support. Collenchyma Back to main anatomy menu Next Back to cell types menu Main menu Cell types Collenchyma Collenchyma cells in a longitudinal section shows the thickening of the primary walls between adjacent stem cells. Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma Collenchyma cells have a thickened primary cell wall that is not lignified. This is in contrast to the rigid, lignified secondary cell walls of cells like sclereids and fibers. The thickening may be somewhat uniform around the cell is a pattern termed lamellar collenchyma. Cytoplasm Back to main anatomy menu Primary wall Middle lamella Back Next Back to cell types menu Main menu Cell types Collenchyma In a second pattern, the collechyma cell wall has additional thickening localized at the corners of each cell and is termed angular collenchyma. In the relatively young cell to the right, deposits are in each corner of adjacent cells. Developing celery petiole Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma The thickening in the middle lamella of mature angular collenchyma cells is evident as an “X-shaped” mark between cells. Cross-section of a celery petiole Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma When intercellular spaces arise between adjacent collenchyma cells it is termed lacunar collenchyma. Tomato stem Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma Compare the appearance of the thickened primary walls of collenchyma cells with the thickened secondary walls a fiber cell that contains lignin. Collenchyma cells with the cell wall stained dark blue. Back to main anatomy menu Back Next Fiber cells with the entire cell wall stained red. Back to cell types menu Main menu Cell types Collenchyma Collenchyma cells and fibers both function to support the stem or leaf, but unlike fibers, collenchyma cells are usually living and retain the ability to elongate. These developing collenchyma cells clearly show a protoplast and nucleus in cells with thickened primary walls. Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma Xylem Collenchyma cells are usually found in groups under the epidermis. Phloem fibers Collenchyma Epidermis Its primary function is in structural support. They are especially prevalent in herbaceous stems and develop early with the ability to elongate as the stem continues to grow. Cross-section of a tomato stem. Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma Collenchyma cells along with fibers and the woody xylem form the three major cell types that provide structural support for plant stems. Epidermis Collenchyma Fibers Xylem Cross-section of English ivy (Hedera helix). Back to main anatomy menu Back Next Back to cell types menu Main menu Cell types Collenchyma Collenchyma cells also provide structural support to leaves. Leaf blade Collenchyma cells are usually located on the abaxial side of the main leaf veins. Vascular bundle Leaf vein Cross-section of a tomato leaf. Back to main anatomy menu Back Collenchyma Back to cell types menu Main menu
