| Term | Definition |
|---|
| adventitious | Roots extending from stems and leaves above ground. |
| annual | A plant that completes its entire life cycle in a single year or growing season. |
| apical dominance | Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth. |
| axillary bud | An embryonic shoot present in the angle formed by a leaf and stem. |
| biennial | A plant that requires two years to complete its life cycle. |
| companion cell | A type of plant cell that is connected to a sieve-tube cell by many plasmodesmata and whose nucleus and ribosomes may serve one or more adjacent sieve-tube cells |
| cork cambium | A cylinder of meristematic tissue in plants that produces cork cells to replace the epidermis during secondary growth. |
| cortex | The region of the root between the stele and epidermis filled with ground tissue |
| cuticle | (1) A waxy covering on the surface of stems and leaves that acts as an adaptation to prevent desiccation in terrestrial plants. (2) The exoskeleton of an arthropod, consisting of layers of protein and chitin that are variously modified for different functions. |
| dermal tissue | The protective covering of plants; generally a single layer of tightly packed epidermal cells covering young plant organs formed by primary growth. |
| 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. |
| epidermis | (1) The dermal tissue system in plants. (2) The outer covering of animals. |
| fibers | A lignified cell type that reinforces the xylem of angiosperms and functions in mechanical support; a slender, tapered sclerenchyma cell that usually occurs in bundles. |
| fibrous root system | Root systems common to monocots consisting of a mat of thin roots that spread out below the soil surface. |
| guard cell | A specialized epidermal plant cell that forms the boundaries of the stomata. |
| internode | The segment of a plant stem between the points where leaves are attached. |
| meristem | Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth. |
| mesophyll | The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis |
| morphogenesis | The development of body shape and organization during ontogeny. |
| node | A point along the stem of a plant at which leaves are attached. |
| perennial | A plant that lives for many years. |
| pericycle | A layer of cells just inside the endodermis of a root that may become meristematic and begin dividing again. |
| periderm | The protective coat that replaces the epidermis in plants during secondary growth, formed of the cork and cork cambium. |
| petiole | The stalk of a leaf, which joins the leaf to a node of the stem. |
| 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. |
| procambium | A primary meristem of roots and shoots that forms the vascular tissue. |
| protoderm | The outermost primary meristem, which gives rise to the epidermis of roots and shoots. |
| protoplast | The contents of a plant cell exclusive of the cell wall. |
| root cap | A cone of cells at the tip of a plant root that protects the apical meristem. |
| root hairs | A tiny projection growing just behind the root tips of plants, increasing surface area for the absorption of water and minerals. |
| root system | All of a plant's roots that anchor it in the soil, absorb and transport minerals and water, and store food. |
| sclereids | A short, irregular sclerenchyma cell in nutshells and seed coats and scattered through the parenchyma of some plants. |
| secondary growth | The increase in girth of the stems and roots of many plants, especially woody, perennial dicots. |
| shoot system | The aerial portion of a plant body, consisting of stems, leaves, and flowers. |
| sieve plates | In a plant, a pore in the end wall of a sieve-tube member through which phloem sap flows. |
| stele | The central vascular cylinder in roots where xylem and phloem are located. |
| stomata | (plural, stomata) 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. |
| taproot | A root system common to eudicots consisting of one large, vertical root (the taproot) that produces many smaller lateral, or branch roots. |
| terminal bud | Embryonic tissue at the tip of a shoot, made up of developing leaves and a compact series of nodes and internodes. |
| tracheids | A water-conducting and supportive element of xylem composed of long, thin cells with tapered ends and walls hardened with lignin. |
| transpiration | The evaporative loss of water from a plant. |
| vascular bundles | A strand of vascular tissues (both xylem and phloem) in a plant stem. |
| vascular cambium | A continuous cylinder of meristematic cells surrounding the xylem and pith that produces secondary xylem and phloem. |
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