| Leaf: | a photosynthetic and transpiring organ usually developing from leaf primordia arising from the shoot apical meristem |
Leaf Components
| Blade: | the flat and laterally-expanded portion of a leaf |
| Leaflet: | a separate blade among others comprising a compound leaf |
| Ligule: | a projection from the top of the sheath on the adaxial side of the sheath-blade joint in grasses |
| Midrib: | the central vein of the leaf blade |
| Midvein: | the central vein of a leaflet |
| Petiole: | a leaf stalk supporting a blade and attaching to a stem at a node |
| Petiolule: | the leaf stalk of a leaflet |
| Pulvinus: | the swollen base of a petiole or petiolule usually involved in leaf movements and leaf orientation |
| Rachilla: | a secondary axis of a multiply-compound leaf |
| Rachis: | main axis of a pinnately compound leaf |
| Sheath: | the proximal portion of a grass leaf usually surrounding the stem |
| Stipels: | paired scales, spines, glands, or blade-like structures at the base of a petiolule |
| Stipules: | paired scales, spines, glands, or blade-like structures at the base of a petiole |
Leaf Anatomy
| Bulliform Cells: | large epidermal cells involved in the rolling of leaves in xerophytic leaves |
| Bundle Sheath: | a layer of cells surrounding the vein with no intercellular spaces; generally involved with phloem loading |
| Guard Cell: | cells occurring in pairs which control the size of the stoma by their turgor pressure |
| Hydathode: | a small gland or stomatal aperture at the end of a vein, through which guttation occurs |
| Lower Epidermis: | the dermal cells of the abaxial (dorsal) surface; generally bearing stomata |
| Palisade Mesophyll: | elongate cells internal to leaf arranged in columns perpendicular to epidermis; generally just under upper epidermis |
| Spongy Mesophyll: | isodiametric cells internal to leaf arranged loosely within blade and usually abaxial (dorsal) to palisade mesophyll |
| Stoma: | small openings for gas exchange and water evaporation |
| Subsidiary =Accessory Cell: | epidermal cells lateral to guard cells and participating in stomatal function |
| Upper Epidermis: | the dermal cells of the adaxial surface; generally window-like; often cutinized |
| Vein: | a vascular bundle in a leaf, consisting of primary xylem and phloem |
Stomatal Distribution
| Amphistomatic: | stomata distributed in both upper and lower epidermis |
| Epistomatic: | stomata confined to upper epidermis |
| Hypostomatic: | stomata confined to lower epidermis |
Stomatal Types
| Actinocytic: | with several subsidiary cells arranged radially around guard cells |
| Anisocytic: | three subsidiary cells, one smaller than the other two |
| Anomocytic: | several irregular subsidiary cells indistinguishable in size, shape, or form from remainder of epidermis |
| Cyclocytic: | with several ranks of more than four concentric subsidiary cells |
| Diacytic: | elongate subsidiary cells with long axis perpendicular to stoma |
| Paracytic: | elongate subsidiary cells with long axis parallel to stoma |
| Tetracytic: | with four subsidiary cells; two lateral, two terminal |
Leaf Types
| Bipinnately compound: | with two orders of leaflets each pinnately compound |
| Compound: | with leaf divided into two or more leaflets |
| Imparipinnately compound =odd-pinnately compound: | with a terminal leaflet |
| Interruptedly pinnately compound: | with larger and smaller leaflests alternating along rachis |
| Palmate-pinnate: | with first order leaflets palmately arranged, second order leaflets pinnately arranged |
| Palmately compound: | leaflets attached at one point at end of petiole |
| Paripinnately compound = even-pinnately compound: | without a terminal leaflet |
| Pinnately compound: | with leaflets arranged oppositely or alternately along the rachis |
| Simple: | a leaf consisting of just one blade and its petiole |
| Ternately compound: | with leaflets in threes |
| Trifoliate: | with three leaflets |
Structural Leaf Types
| Bract: | modified leaf within the inflorescence | |
| Bracteole: | smalll leaf usually on a pedicel | |
| Chaff: | scale or bract at base of tubular flower in composites | |
| Complete: | leaf with blade, petiole, and stipules | |
| Cotyledon: | embryonic leaf | |
| Elaminate: | bladeless | |
| Epetiolate =sessile: | lacking a petiole | |
| Glume: | bract usually in pairs at the base of a grass spikelet | |
| Incomplete: | leaf without one of: | blade, petiole, stipule |
| Lemma: | outer scalae subtending grass floret | |
| Palea: | inner scale subtending grass floret | |
| Phyllary: | one of the involucral leaves subtending an inflorescence as in composites | |
| Phyllodium: | a flattened blade-like petiole or midrib | |
| Pitcher: | ventricose to tubular insectivorous leaf as in pitcher plant | |
| Scale: | a small non-green leaf on a bud or a modified stem | |
| Spathe: | an enlarged bract enclosing an inflorescence as in aroids | |
| Sporophyll: | a spore-bearing leaf | |
| Storage leaf: | succulent leaf | |
| Tendril: | a coiled rachis or twining leaflet | |
| Tentacular: | glandular-haired or tentacle-bearing insectivorous leaf as in sundew |
Leaf Arrangement
| Alternate: | one leaf per node |
| Decussate: | opposite leafes at right angle to preceding pair |
| Distichous: | leaves in two rows along stem |
| Opposite: | two leaves per node on opposite sides of the stem |
| Phyllotaxis: | the arrangement of leaves |
| Rosulate: | leaves in a rosette |
| Tetrastichous: | leaves in four rows along stem |
| Tristichous: | leaves in three rows along stem |
| Whorled =radiate =verticillate: | three or more leaves per node |
Leaf Transverse Posture
| Applanate: | flat, without curves or bends |
| Arcuate: | curved like a crescent, downward or upward |
| Cernuous: | drooping |
| Flexuous: | with a series of long or open vertical curves at right angles to the central axis |
| Geniculate: | abruptly bent vertically near base |
| Incurved: | curved inward or upward |
| Recurved: | curved outward or downward |
| Squarrose: | curved sharply downward or outward near the apex |
| Undulate: | with a series of vertical curves |
Leaf Longitudinal Posture
| Conduplicate: | longitudinally flolded upward or dowward along central axis |
| Involute: | margens rolled inward over upper surface |
| Plicate: | with a series of folds, pleated |
| Revolute: | margins rolled outward or downward over lower surface |
| Sinuate: | long curves parallel to the central axis |
| Tortuous: | irregularly twisted |
| Valvate: | sides enrolled so that the margins touch |
General Positions
| Abaxial =dorsal: | away from the axis, the lower epidermis |
| Adaxial =ventral: | toward the axis, the upper epidermis |
| Apical: | at or near the tip of the leaf |
| Basal: | at or near the bottom |
| Distal: | away from the point of origin or attachment |
| Marginal: | toward or at the edge |
| Proximal: | toward the point of origin or attachment |
Blade Lobes
| Bifid: | divided into two lobes |
| Cleft: | lobed only 1/4 to 1/2 to middle of blade |
| Dichotomous: | divided into equal parts |
| Dimidiate: | divided into unequal parts |
| Dissected: | cut into numerous segments |
| Divided: | cut 3/4 to almost complete length |
| Furcate: | forked |
| Incised: | margins sharply, deeply, and jaggedly cut |
| Lacerate: | appearing torn |
| Laciniate: | torn into ribbonlike or straplike segments |
| Lobed: | round-toothed 1/8 to 1/4 to middle of blade |
| Parted: | cut 1/2 to 3/4 of distance to middle of blade |
| Pinnatifid: | cut pinnately |
| Plamatifid: | palmately lobed |
| Quadrifid: | divided into four lobes |
| Serrated: | cut into sawlike teeth |
| Trifid: | divided into three lobes |
Blade Shapes
| Acicular: | needle-like |
| Auriculiform: | obovate with two small rounded basal lobes |
| Cordate: | heart-shaped |
| Elliptic: | with blade widest at midpoint and symmetrically curved margins |
| Falcate: | scimitar-shaped |
| Filiform: | thread-like |
| Half-terete: | half-cylindrical |
| Hastate: | obovate with two pointed basal lobes extending laterally |
| Ligulate: | strap-shaped |
| Linear: | with a very narrow blade |
| Lyrate: | lobed with larger terminal lobe and smaller symmetrical proximal lobes |
| Oblong: | with blade widest at midpoint and almost-parallel margins |
| Obovate: | with blade widest distal to the midpoint and curved margins |
| Obtriangular: | with blade widest at apex and tapering to the base |
| Obtrullate: | with blade widest distal to the midpoint and margins angled at widest point |
| Ovate: | with blade widest proximal to the midpoint and curved margins |
| Peltate: | umbrelliform with petiole attached in middle of lower epidermis |
| Reniform: | suborbiculate leaf, kidney-shaped |
| Rhombic: | with blade widest at midpoint and margins angled at midpoint |
| Runcinate: | oblanceolate with lacerate to parted margins |
| Saggitate: | obovate with two pointed basal lobes extending proximally |
| Spatulate: | obovate tapering toward base, club-shaped |
| Terete: | cylindrical |
| Triangular: | with blade widest at proximal extreme and tapering to the apex |
| Trullate: | with blade widest proximal to the midpoint and margins angled at widest point |
Leaf Apex Angle
| Acuminate: | terminal angle less than 45¡ |
| Acute: | terminal angle between 45 and 90¡ |
| Obtuse: | terminal angle greater than 90¡ |
| Rounded: | margins and apex forming a smooth arc |
| Truncate: | cut straight across, blade ending at right angles to midrib |
Leaf Apex Notched
| Cleft: | blade notched at end 1/4-1/2 distance to midpoint of blade |
| Cordate: | blade notched at end 1/8-1/4 distance to midpoint of blade |
| Emarginate: | blade notched at end 1/16-1/8 distance to midpoint of blade |
| Retuse: | blade notched at end less than 1/16 distance to midpoint of blade |
Leaf Apex Extensions
| Apiculate: | extension more than 3length:1width, slightly curved or flexuous |
| Aristate: | extension more than 3length:1width, straight or stiff |
| Cirrhous: | extension more than 10length:1width, coiled and flexuous |
| Cuspidate: | triangular, tooth-like extension |
| Mucronate: | extension less than 3length:1width, straight or stiff |
| Mucronulate: | extension 2length:1width, straight |
Veination
| Dichotomous: | with veins brancing into equal pairs |
| Netted =reticulate: | with veins forming a network |
| Palmate: | with three or more veins arising from common point near base of blade |
| Parallel: | with veins extending from base to apex, esssentially parallel |
| Penni-parallel: | with veins extending from midrib to margins, essentially parallel |
| Pinnate: | with secondary veins arising from midrib |
Surface
| Aciculate: | marked with pin-pricks |
| Alate: | winged |
| Alveolate: | honeycombed |
| Areolate: | divided into angular or squarish space |
| Bullate: | puckered or blistered |
| Canaliculate: | longitudinally groved in relation to petioles and midrib |
| Clathrate: | latticed |
| Corrugate: | ridged |
| Costate: | coarsely ribbed |
| Fenestrate: | with window-like holes |
| Flexuous: | coarsely undulate with folds at right angles to long axis |
| Foveolate: | pitted |
| Plicate =plaited: | folded longitudinally |
| Punctate: | with small impressions or depressions |
| Pustulate: | with scattered blister-like swellings |
| Reticulate: | netted |
| Ribbed: | with longtitudinal ridges |
| Rugose: | covered with coarse reticulate lines |
| Smooth: | without obvious configuration |
| Striate: | with longitudinal lines |
| Sulcate: | with longitudinal grooves |
| Tortuous: | surface twisted |
Surface trichomes
| Aculeate: | prickly |
| Bristly: | with bristles |
| Comose: | with apical tuft of trichomes |
| Downy: | with short soft trichomes |
| Echinate: | with spines |
| Farinaceous: | mealy |
| Glabrous: | smooth, without hairs |
| Glandular: | with glandular hairs |
| Glaucous: | with a waxy coating |
| Glutinous: | with a shiny, sticky surface |
| Greasy: | slick, oily, slippery to touch |
| Hirsute: | with long stiff trichomes |
| Mucilaginous: | gummy or gelatinous |
| Pilose: | with soft shaggy trichomes |
| Prickly: | with prickles |
| Pruinose =sebiferous: | with heavy wax coating |
| Pubescent: | covered with trichomes |
| Pubescent: | with straight, slender trichomes |
| Pulverulent: | covered with fine powdery wax granules |
| Resinous: | with yellowish sticky exudate |
| Scabrous: | with harsh surface |
| Spiculate: | with crystals on the surface |
| Squamose: | with coarse scales |
| Strigose: | with sharp bent trichomes |
| Tomentose: | with dense, interwoven trichomes |
| Tuberculate =verrucose: | warty |
| Velutinous: | with dense, straight, long, soft trichomes; pelt-like |
Trichome Types
| Barbed: | with small hooks along length |
| Clavate: | club-shaped |
| Conical: | tapered to tip |
| Cylindrical: | with parallel edges; not tapering |
| Dendritic: | tree-like with limbs and branchlets |
| Echinoid: | a patch of many trichomes |
| Falcate: | talon-shaped |
| Forked: | branched trichome |
| Glandular: | swollen cells on shorter stalk, sometimes multicellular and secretory |
| Moniliform: | with each cell wider at middle; beaded-looking |
| Multicellular: | consisting of a column of cells |
| Multiseriate: | trichome more than one cell wide |
| Papillate: | small protuberance |
| Peltate: | umbrella-like |
| Stellate: | star-like |
| Strigose: | curved |
| Uncinate: | multicellular with terminal cells curving sharply |
| Unicellular: | consisting of one cell |
| Uniseriate: | trichome one cell wide |
This page © Ross E. Koning 1994.
The CBE citation style for this page would be: Koning, Ross E. 1994. "Leaf Vocabulary". Plant Physiology Website. http://koning.ecsu.ctstateu.edu/plant_biology/leafvocab.html (your visit date)
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