LEAVES

Vocabulary practice flashcards covering leaf anatomy, functions, internal tissue layers, developmental patterns, and morphological adaptations based on Chapter 6.

Leaf Blade (Lamina)

The flat, wide, light-harvesting portion of a foliage leaf optimized for sunlight interception and carbon dioxide absorption.

Dorsal Surface (Abaxial Side)

The lower side of a leaf blade where major vascular veins characteristically protrude outward.

Ventral Surface (Adaxial Side)

The upper, typically smooth surface of a leaf blade.

Petiole

The stalk that holds the leaf blade out into the light to avoid self-shading and allows fluttering in the wind to cool the leaf and replenish carbon dioxide.

Sessile Leaf

A leaf that lacks a petiole, attaching its blade directly to the stem.

Sheathing Leaf Base

A modified basal portion of a leaf found in many monocots that wraps around the stem to provide attachment and flexibility without a petiole.

Simple Leaf

A leaf whose blade consists of just a single undivided piece of tissue.

Compound Leaf

A leaf having a blade divided into several separate, individual parts termed leaflets.

Leaflet

An individual blade of a compound leaf that is attached by a petiolule to a rachis and lacks an axillary bud at its base.

Rachis

The central stalk or extension of the petiole in a compound leaf along which individual leaflets are attached.

Petiolule

The small stalk that attaches an individual leaflet to the rachis in a compound leaf.

Parts of a Compound Leaf

The anatomical components of pinnately and palmately compound leaves, including the petiole, rachis, petiolules, and leaflets.

Palmately Compound Leaf

A compound leaf in which all leaflets attach at the same single point at the apex of the petiole.

Pinnately Compound Leaf

A compound leaf in which leaflets attach individually in two rows along the length of an elongated rachis.

Doubly Compound Leaf

A compound leaf in which the primary rachis bears leaflets that are themselves subdivided into pinnately arranged secondary leaflets.

Leaf Shapes

Morphological blade forms including cordiform (heart-shaped), hastiform (spear-shaped with spreading basal lobes), peltiform (shield-shaped with petiole attached centrally), and sagittiform (arrowhead-shaped with downward-pointing lobes).

Leaf Margins

The physical edge contours of a leaf blade, including entire (smooth), dentate (toothed), divided (deeply cut), lacerate (irregularly cut), and serrate (saw-toothed).

Reticulate Venation

A netted branching pattern of vascular bundles characteristic of the leaves of basal angiosperms and eudicots.

Parallel Venation

A venation pattern characteristic of long, strap-shaped monocot leaves in which major veins run side by side with fine transverse connections.

Abscission Zone

A specialized transverse zone of cells situated at the base of the petiole that weakens enzymatically to cut off an aged or damaged leaf cleanly.

Leaf Scar

The protective corky scar tissue formed by adjacent undamaged stem cells across the wound created after a leaf abscises.

Transpiration

The evaporative loss of water vapor from the plant body through the leaf epidermis and open stomata.

Stomatal Crypt

A sunken cavity in the leaf epidermis that shelters stomata and trichomes from moving air, slowing transpiration.

Mesophyll

The internal ground tissues of a leaf located between the upper and lower epidermis.

Palisade Parenchyma

The main photosynthetic tissue of a leaf, situated below the upper epidermis and consisting of columnar, chlorophyll-rich cells separated by slight intercellular spaces.

Spongy Mesophyll

A loose, open aerenchyma located in the lower region of a leaf that allows rapid internal diffusion of carbon dioxide away from stomata.

Midrib (Midvein)

The primary, central longitudinal vascular bundle of a leaf blade, containing primary xylem on its upper side and primary phloem on its lower side.

Minor Veins

The narrowest leaf vascular bundles, which lack nonconducting fibers and maximize surface contact to release water from xylem and load photosynthesized sugars into phloem.

Bundle Sheath

A protective cylinder of fibers or parenchyma cells enclosing leaf vascular bundles that provides mechanical support and deters herbivorous insects.

Bundle Sheath Extension

A mass of fibers extending from a leaf vascular bundle to the upper or lower epidermis, conferring blade rigidity and conducting water outward via capillary action.

Leaf Trace

A vascular bundle that branches off from the stem vascular cylinder and diverges into the petiole of an adjacent leaf.

Stipules

Small flaps of tissue born in pairs at the base of the petiole that serve to protect the young shoot apex or provide supplemental photosynthesis.

Leaf Primordium

An initial cone-shaped outward protrusion formed by meristematic cell division at the base of a shoot apical meristem that develops into a leaf.

Basal Meristem

A localized meristematic zone situated at the base of linear monocot leaf blades that allows continuous growth and regeneration following grazing or mowing.

Succulent Leaves

Thick, fleshy leaves with low surface-to-volume ratios, minimal internal air space, and extensive water-storage parenchyma that conserve water in desert habitats.

Sclerophyllous Foliage Leaves (Sclerophylls)

Tough, hard perennial leaves reinforced with abundant sclerenchyma, thick cuticles, and waxes that function for $2$ or more years.

Bud Scales

Small, tough, waxy modified leaves with short or absent petioles that wrap tightly around dormant shoot apical meristems to protect them from winter drying and freezing.

Spines

Modified leaves of axillary buds that lack a photosynthetic lamina and vascular tissues, consisting instead of closely packed, lignified, non-living fibers.

Tendrils

Modified blade-free leaves exhibiting indeterminate growth that sense physical contact and coil around solid objects to support climbing stems.

Kranz Anatomy

A specialized leaf anatomy in $C_4$ plants lacking distinct palisade and spongy layers, featuring prominent bundle sheaths of large green cells encircled by radiating mesophyll cells.

Insect Traps

Modified leaves (classified as passive pitchers or active traps like sundews and Venus' flytraps) specialized to capture and digest insects to obtain nitrogen in nutrient-poor environments.

Nicotine

A lethal defensive alkaloid found in tobacco leaves ($0.6\%$ to $9.0\%$) that readily penetrates mucous membranes and causes heart disease and cancer in humans.

Phelloderm

Chloroplast-containing cells produced by the cork cambium in green bark (such as in palo verde) that carry out recycling photosynthesis by recapturing respired carbon dioxide.

Cortical Bundles

An extensive three-dimensional network of collateral vascular bundles in cactus stems that vascularizes the thick, succulent photosynthetic cortex.