| A | B |
|---|
| epidermal cell | cell that makes up the dermal tissue, which is the outer covering of a plant |
| vessel element | in angiosperms, xylem cell that forms part of a continuous tube through which water can move |
| sieve tube element | phloem cell that is joined end-to-end to similar cells to form sieve tubes |
| companion cell | A type of plant cell that is connected to a sieve-tube member by many plasmodesmata and whose nucleus and ribosomes may serve one or more adjacent sieve-tube members |
| parenchyma | A relatively unspecialized plant cell type that carries most of the metabolism, synthesizes and stores organic products, and develops into more differentiated cell types |
| collenchyma | A flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth |
| scleremchyma | A rigid, supportive plant cell type usually lacking protoplasts and possessing thick secondary walls strengthened by lignin at maturity |
| meristem | Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth. |
| meristematic tissue | plant tissue found only in the tips of shoots and roots |
| apical meristem | Embryonic plant tissue in the tips of roots and in the buds of shoots that supplies cells for the plant to grow in length. |
| differentiation | The structural and functional divergence of cells as they become specialized during a multicellular organism's development; dependent on the control of gene expression |
| taproot | primary root found in some plants that grows longer and thicker than other roots |
| fibrous root | part of a root system in which roots branch to such an extent that no single root grows larger than the rest |
| root hair | A tiny projection growing just behind the root tips of plants, increasing surface area for the absorption of water and minerals. |
| cortex | The outer, as opposed to the inner, part of an organ, as in the adrenal gland |
| endodermis | The innermost layer of the cortex in plant roots; a cylinder one cell thick that forms the boundary between the cortex and the stele |
| vascular cylinder | A continuous cylinder of meristematic cells surrounding the xylem and pith that produces secondary xylem and phloem |
| root cap | A cone of cells at the tip of a plant root that protects the apical meristem |
| casparian strip | A water-impermeable ring of wax around endodermal cells in plants that blocks the passive flow of water and solutes into the stele by way of cell walls |
| node | A point along the stem of a plant at which leaves are attached |
| internode | The segment of a plant stem between the points where leaves are attached |
| bud | In plants, an embryonic shoot, including rudimentary leaves, often protected by special bud scales |
| vascular bundle | In plants, a group of longitudinal supporting and conducting tissues |
| pith | The core of the central vascular cylinder of monocot roots, consisting of parenchyma cells, which are ringed by vascular tissue; ground tissue interior to vascular bundles in dicot stems |
| primary growth | Growth initiated by the apical meristems of a plant root or shoot |
| secondary growth | The increase in girth of the stems and roots of many plants, especially woody, perennial dicots |
| vascular cambium | A continuous cylinder of meristematic cells surrounding the xylem and pith that produces secondary xylem and phloem |
| cork cambium | A cylinder of meristematic tissue in plants that produces cork cells to replace the epidermis during secondary growth |
| heartwood | older xylem near the center of a woody stem that no longer conducts water |
| sapwood | area in plants that surrouns heart and is active in fluid transport |
| bark | All tissues external to the vascular cambium in a plant growing in thickness, consisting of phloem, phelloderm, cork cambium, and cork |
| blade | The broad, expanded part of a leaf |
| petiole | The stalk of a leaf, which joins the leaf to a node of the stem |
| mesophyll | specialized ground tissue that makes up the bulk of most leaves |
| palisade mesophyll | In plant leaves, the columnar, chloroplast-containing parenchyma cells of the mesophyll |
| spongy mesophyll | In plant leaves, a tissue composed of loosely arranged chloroplast-containing parenchyma cells |
| stoma | A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant |
| guard cell | A specialized epidermal plant cell that forms the boundaries of the stomata |
| transpiration | The evaporative loss of water from a plant |
