Leaf Vocabulary

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
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
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
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
Auriculiform:obovate with two small rounded basal lobes
Elliptic:with blade widest at midpoint and symmetrically curved margins
Hastate:obovate with two pointed basal lobes extending laterally
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
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

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

Aciculate:marked with pin-pricks
Areolate:divided into angular or squarish space
Bullate:puckered or blistered
Canaliculate:longitudinally groved in relation to petioles and midrib
Costate:coarsely ribbed
Fenestrate:with window-like holes
Flexuous:coarsely undulate with folds at right angles to long axis
Plicate =plaited:folded longitudinally
Punctate:with small impressions or depressions
Pustulate:with scattered blister-like swellings
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
Bristly:with bristles
Comose:with apical tuft of trichomes
Downy:with short soft trichomes
Echinate:with spines
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
Conical:tapered to tip
Cylindrical:with parallel edges; not tapering
Dendritic:tree-like with limbs and branchlets
Echinoid:a patch of many trichomes
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
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)

Go back to the Course Schedule.

Go back to Ross Koning's Home Page.

Send comments and bug reports to Ross Koning at koning@easternct.edu.

View the Standard Disclaimer.