| Callus |
Growing mass of unorganized parenchyma cells produced in response to wounding. |
| Casparian strip |
A band-like deposit of waterproof suberin that wraps around each cell in the endodermis and forces water to move through the cells rather than the intercellular spaces. |
| Cell membrane |
Made up of layers of protein and lipid (fats and oils are examples of lipids) and semi-permeable, meaning that it allows select compounds in and out, but blocks other types of compounds. |
| Cell wall |
Rigid membrane that contains cellulose (a carbohydrate that is indigestible for humans) and is the outer covering of the cell. |
| Chloroplast |
Organelle that contains chlorophyll where light energy is captured and where the first steps are taken in the chemical pathway that converts the energy in light into forms of energy that the plant can transport and store, like sugar and starch. |
| Chromoplasts |
Cellular organelles that contain types and colors of pigments other than the chlorophyll found in chloroplasts. |
| Collenchyma |
Elongated cell type with thicker walls; usually arranged in strands; provides support. |
| Companion cells |
Associated with sieve tube members (direct the metabolism) and containing a nucleus (alive). |
| Cytoplasm |
Fluid inside the cell membrane in which the organelles and other plant cell parts are suspended. |
| Dermal tissue |
Tissue on the outside of the plant; provides protection for the plant cells it surrounds. |
| Endodermis |
Innermost cells of the cortex. |
| Epidermis |
Outermost layer of cells in the plant. |
| Ground meristem |
New, primarily parenchyma, cells lying between the protoderm and procambium that will mature to become the cortex tissue. |
| Mesophyll |
Site of most photosynthesis reactions in the leaf; located in the middle layer of the leaf. |
| Middle lamella |
Material containing pectin that forms between cells and that cements the cell wall of one cell to the cell wall of an adjacent cell. |
| Mitochondria |
Organelle where stored sugars are metabolized to produce forms of energy that the plant can use for growth; the cell’s power plant. |
| Nucleus |
Organelle that contains the chromosomes. Chromosomes contain the genetic code that is carried within each cell and that directs which chemical reactions are turned on and off in the cell. |
| Organelle |
Generic term for a plant organ. |
| Palisade mesophyll |
Densely packed, columnar-shaped, elongated cells full of chloroplasts. Analogous to cortex parenchyma cells in the stem, but in the leaf are specialized for light energy capture. |
| Parenchyma |
Cell type with thin cell walls; unspecialized, but carries on photosynthesis and cellular respiration and can store food; forms the bulk of the plant body. |
| Pericycle |
Single layer of tightly packed cells located in the vascular cylinder that retain the ability to divide and produce new cells; source of lateral roots. |
| Sclerenchyma |
Cell type with thickened, rigid, secondary walls that are hardened with lignin; provides support for the plant. |
| Sieve tube members |
Elongated cells that join end to end to form tubes for passage of liquids. The end walls have pores. Unlike xylem cells, these cells are still alive. They have a thin cell membrane containing a layer of living protoplasm that hugs the wall of the cell. |
| Spongy mesophyll |
Loosely packed cells with large air spaces between the cells, allowing movement and exchange of gases, specifically oxygen, carbon dioxide, and water vapor. Also contain chloroplasts. |
| Tissue |
Group of cells that share a function. |
| Tracheids |
Elongated and narrower than vessels, connected by overlapping at their ends, dead at maturity, and containing pits through which water can move. |
| Vacuole |
Organelle containing various fluids including stored chemical energy like starch and waste products from the cell. Takes up much of the cell volume and gives shape to the cell. |
| Vessels |
Elongated xylem cells that connect end to end to form tubes, are dead at maturity, and have perforated end walls so water can move freely through the holes and flow from cell to cell. Vessels have a relatively large diameter compared to other xylem cells and allow greater movement of water. |
