Chapter 3: Terms
Here are the terms from this chapter that you will need to be familiar with.
| Adventitious | Tissue arising from an organ other than expected. |
| Adventitious roots | Roots that emerge from the stem rather than roots. |
| Alternate leaves | Leaves are attached on alternate sides as they go up the stem. |
| Apex | Tip of the stem. |
| Apical bud | Bud located on the tip of the stem. |
| Apical meristem | Group of more or less continually dividing cells located at the tip of a shoot or root. |
| Axil | Upper angle between a lateral structure and the stem to which it is attached. |
| Axillary bud | Bud borne in the axil of a stem. |
| Axillary meristem | Group of more or less continually dividing cells located at the axils of a stem. |
| Basal root | Root that emerges from the region just above where the main stem stops and the root begins. |
| Bract | Leaf attached to the terminal node, which is part of the inflorescence rather than the stem. It may also be found at the base of each pedicel. |
| Branch | Vegetative growth coming from a node on the main stem. |
| Bud | Immature vegetative or floral shoot or both, often covered by scales; also called a meristem. |
| Chlorophyll | Green photosynthetic pigment found in plants, algae, and cyanobacteria that captures light for photosynthesis. |
| Compound leaf | Leaf with a blade margin that is completely interrupted and segmented into separate leaflets. |
| Fibrous root | Root system where the radicle grows and then rapidly slows or completely halts in growth. Once this happens, roots will emerge above the radicle and from the stem tissue located below the soil. |
| Hypocotyl roots | Roots that emerge above the basal roots. |
| Internode | Stem regions between nodes in plants. |
| Lamina | Another name for a leaf blade. |
| Lateral or secondary roots | Roots that extend horizontally from the primary root and serve to anchor the plant securely into the soil. This branching of roots also contributes to water uptake, and facilitates the extraction of nutrients required for the growth and development of the plant. |
| Leaf | A usually green, flattened, lateral structure attached to a stem and functioning as a principal organ of photosynthesis and transpiration in most plants. |
| Leaf axil | Upper angle between a leaf petiole and the stem to which it is attached. |
| Leaf blade | Broad portion of a leaf; does not include the petiole. |
| Leaf margin | Edge of the leaf blade. |
| Leaf primordia | Young leaves, recently formed by the shoot apical meristem, located at the tip of a shoot. |
| Leaf scar | Mark indicating the former place of attachment of petiole or leaf base. |
| Leaf sheath | Structure where the blade attaches to an envelope of leaf tissue that wraps around the shoot of the plant and attaches to a lower node on the stem. |
| Leaflet | Small leaf-like structure that is found on compound leaves. Multiple leaflets make up a single compound leaf. |
| Lenticel | Small opening in the cork of woody stems that allows for gas exchange. |
| Meristem | Group of continuously dividing cells; also called a bud. |
| Midrib | Main vein, generally in the center of the leaf, from which secondary veins emerge. |
| Node | Stem region of a plant where one or more leaves attach; location of lateral buds. |
| Opposite leaves | Leaves that grow directly opposite each other on the stem. |
| Palmate venation | Where several veins radiate from the point where the petiole attaches to the blade. The veins fork, travel a bit, fork again, travel, fork, and so on until they reach the margin of the leaf. |
| Palmately compound leaf | Compound leaf where the petiolules of the leaflets connect directly to the petiole (no rachis). |
| Parallel venation | Distribution or arrangement of a system of veins in a leaf blade in a non-intersecting network. The veins are parallel to each other and the long edge of the leaf. |
| Petiole | Stalk by which most leaves are attached to a stem; part of the leaf structure, not the stem. |
| Petiolule | Stalk that connects the leaflet to the top of the petiole. |
| Pinnate venation | Type of webbed venation where there is a strong midrib and the secondary veins fan out opposite one other. |
| Pinnately compound leaf | Compound leaf where the leaflets are arranged opposite one another on the rachis. |
| Primary meristem | Apical meristems on the shoot and root apices in plants that produce plant primary tissues. |
| Primary root | Root that forms from the embryonic radicle. |
| Prop root | Adventitious root that arises from the stem, penetrates the soil, and helps support the stem, as in corn. |
| Radicle | Embryonic root that breaks through the seed coat during germination and develops into the seedling’s root system. |
| Rhizome | Horizontal stem growing just below the soil surface. |
| Root | Organ that anchors the plant into the soil, takes up water and nutrients, and stores food. |
| Root hair | Thin, hairlike outgrowth of an epidermal cell of a plant root that absorbs water and minerals from the soil. Root hairs live for only a few weeks, deteriorate, and are then replaced by fresh root hairs. |
| Sessile | When a leaf lacks a petiole; called a sessile leaf. |
| Shoot | Made up of a central axis (stem) with a repeating pattern of nodes and internodes. |
| Simple leaf | Leaf with an uninterrupted blade margin. |
| Stem | Supporting and conducting organ usually developed initially from the epicotyl and growing upward, and consisting of nodes and internodes. |
| Stipule | Usually a pair of appendages located at the base of a leaf but may be fused into a ring around the stem; variable in size, shape, and texture; serves for protection or to attract pollinators. |
| Stolon | Stem with long internodes that grows along the surface of the ground. |
| Storage root | Root that is modified for storage of nutrients, such as carrots and beets. |
| Tap root | Main root of a plant, usually stouter than the lateral roots and growing straight downward from the stem. |
| Terminal bud | Bud located at the apex of a stem. |
| Trifoliate leaf | Compound leaf with three leaflets that attach to a rachis. |
| Tuber | Swollen, underground, modified stems that store food. |
| Venation | Pattern of veins on a leaf. |
| Whorled leaves | Leaves oriented in a whorled formation in which their point of attachment appears to spiral up the stem. |
