Plant Organs: Leaves – Lecture Review

Vocabulary flashcards covering structure, function, adaptations, anatomy, and economic importance of leaves.

Photosynthesis (in leaves)

Process where light energy is converted into chemical energy, producing glucose from CO2 and H2O.

Gaseous Exchange (leaf)

Intake of CO2 and release of O2 during photosynthesis; intake of O2 and release of CO2 during respiration.

Transpiration

Loss of water vapor from leaf surfaces.

Xerophyte Leaf Adaptations

Thick, reduced leaves; thick waxy cuticle; stomata open only at night.

Floating Leaf Adaptation

Stomata present only on upper epidermis.

Submerged Leaf Adaptation

Leaves lack stomata entirely.

Conifer Leaf Adaptations

Evergreen, needle-like leaves with thick waxy cuticle and sunken stomata.

Simple Leaf

Single blade attached to a petiole from one axillary bud.

Compound Leaf

Blade divided into leaflets arising from one axillary bud.

Pinnately Compound Leaf

Leaflets in pairs along an extension of the petiole (rachis).

Palmately Compound Leaf

All leaflets attach at one point at end of petiole.

Leaf Attachment: Petiolate

Leaf attached to stem by a petiole.

Leaf Attachment: Sessile

Leaf lacking a petiole; blade attaches directly to stem.

Leaf Attachment: Sheathing

Base of leaf wraps partly or wholly around stem.

Leaf Attachment: Clasping

Blade partly surrounds stem but is not fully sheathing.

Leaf Attachment: Perfoliate

Stem appears to pass through the blade.

Leaf Attachment: Connate

Opposite leaves fused around the stem.

Linear Leaf Shape

Very narrow, parallel sides; e.g., grasses.

Lanceolate Leaf Shape

Lance-shaped; wider below middle, tapering to tip.

Ovate Leaf Shape

Egg-shaped with broader base.

Cordate Leaf Shape

Heart-shaped with notch at base.

Leaf Venation: Parallel

Veins run side-by-side along length of blade; typical of monocots.

Pinnately Netted Venation

Single midvein with smaller lateral veins branching; eudicots.

Palmately Netted Venation

Several primary veins fan from base of blade.

Phyllotaxy: Alternate

One leaf per node in spiral arrangement.

Phyllotaxy: Opposite

Two leaves attached at each node on opposite sides.

Phyllotaxy: Whorled

Three or more leaves arise from a single node.

Leaf Apex: Acuminate

Long tapering point, concave sides.

Leaf Apex: Acute

Sharp angle point, straight sides.

Leaf Margin: Entire

Smooth, un-lobed edge.

Leaf Margin: Serrate

Saw-toothed edge with forward-pointing teeth.

Leaf Base: Cuneate

Wedge-shaped base.

Leaf Base: Auriculate

With ear-like lobes at base.

Cuticle

Waxy covering over epidermis that reduces water loss and pathogen entry.

Palisade Mesophyll

Columnar cells rich in chloroplasts beneath upper epidermis; major photosynthesis site.

Spongy Mesophyll

Loosely packed cells with air spaces facilitating gas exchange.

Bundle Sheath

Layer of cells surrounding vascular bundle, regulates movement in/out of veins.

Guard Cells

Specialized epidermal cells that control stomatal opening.

Stomata

Pores in epidermis allowing gas exchange; usually abundant on lower surface.

Trichomes

Leaf hairs that reduce water loss and deter herbivores.

Factors Opening Stomata

Light, adequate water, moderate temperature promote opening.

Factors Closing Stomata

Darkness, water stress, high temperature encourage closure.

CO2 & Stomatal Density

High atmospheric CO2 correlates with lower stomatal density; low CO2 with higher density.

Monocot Leaf Features

Narrow blade, sheath around stem, parallel venation, isobilateral mesophyll.

Eudicot Leaf Features

Broad blade with petiole, netted venation, distinct palisade & spongy layers.

Bulliform Cells

Large upper-epidermis cells in many grasses that fold leaf during drought.

Cotyledon

Seed leaf containing stored food for germinating embryo.

Colored Bract

Pigmented leaf-like structure attracting pollinators (e.g., poinsettia).

Insect-Trapping Leaf

Modified leaf that captures and digests insects for nutrients (e.g., Venus flytrap).

Tendril

Leaf or leaflet modified into slender coil for climbing support.

Spine (Leaf)

Reduced, sharp leaf protecting plant and minimizing water loss (cactus).

Storage Leaf

Succulent leaf storing water in large vacuoles.

Absorptive Leaf

Submerged leaf lacking stomata that absorbs dissolved nutrients (e.g., Hydrilla).

Reproductive Leaf

Leaf that produces plantlets along margins (e.g., Kalanchoë).

Flower-Pot Leaf

Leaf forming cup to collect water/debris for nutrients (fairy-elephant’s-feet).

Window Leaf

Leaf mostly buried with a transparent top for light, conserving water in arid sites.

Leaf Abscission

Process by which leaves detach from stem via specialized abscission zone.

Separation Layer (Abscission)

Cell layer where middle lamella is dissolved, causing leaf drop.

Protective Layer (Abscission)

Cork cells that seal scar after leaf falls, preventing water loss/pathogen entry.

Economic Uses: Food Leaves

Edible leaves like lettuce, spinach, cabbage provide nutrition.

Economic Uses: Fiber Leaves

Leaves yielding fibers such as abaca, pineapple, jute.

Economic Uses: Drugs from Leaves

Medicines like digitalis derived from foxglove foliage.