Plant Morphology & Anatomy – Leaf Structure and Function

Vocabulary flashcards covering key anatomical, developmental, and functional terms related to leaf morphology and physiology as presented in the lecture.

Leaf (Megaphyll)

A determinate, flat organ with branched veins optimized for light capture and gas exchange; characteristic of euphyllophytes (ferns, gymnosperms, angiosperms).

Lycophyll

Small, scale-like leaf of lycophytes with a single, unbranched vein.

Euphyllophytes

Major vascular-plant clade (ferns, gymnosperms, angiosperms) possessing true leaves with complex venation.

Leaf Primordium

Initial outgrowth from the shoot apical meristem that develops into a leaf.

Lamina (Blade)

Flattened, photosynthetic part of a leaf.

Petiole

Stalk that attaches the leaf blade to the stem; contains vascular traces.

Dorsiventral Leaf

Leaf with distinct upper (adaxial) palisade layer and lower (abaxial) spongy layer.

Palisade Mesophyll

Columnar, chloroplast-rich cells beneath the upper epidermis that channel light downwards.

Spongy Mesophyll

Loosely arranged lower mesophyll with large air spaces aiding CO₂ diffusion.

Mesophyll

Collective term for palisade and spongy photosynthetic tissues inside a leaf.

Chlorenchyma

Parenchyma tissue containing chloroplasts; synonymous with photosynthetic mesophyll.

Stomata

Pores in the epidermis that regulate gas exchange and water loss.

Guard Cells

Paired, chloroplast-containing cells that open and close each stoma.

Subsidiary Cells

Epidermal cells originating with guard cells that assist stomatal function.

Dumbbell Guard Cells

Monocot guard-cell shape in which bulbous ends inflate/deflate to open or close the pore.

Cuticle

Waxy, hydrophobic layer of cutin and waxes covering the epidermis to limit water loss.

Epicuticular Waxes

Surface wax projections that create hydrophobicity (e.g., Lotus effect).

Multiple Epidermis

Two or more cell layers derived from protoderm forming the leaf surface (e.g., Ficus).

Hypodermis

Extra sub-epidermal layers derived from ground meristem, often devoid of chloroplasts, adding toughness.

Trichome

Hair-like epidermal outgrowth that can deter herbivores, reflect light, or secrete substances.

Intercalary Meristem

Meristem near the leaf base in grasses enabling continual elongation after grazing or mowing.

Parallel Venation

Venation pattern of most monocots where major veins run side-by-side along leaf length.

Pinnate (Feather) Venation

One main midrib with secondary veins branching laterally, common in eudicots.

Palmate Venation

Several main veins radiating from a single point at the leaf base.

Reticulate (Netted) Venation

Fine network of interconnecting minor veins between larger veins.

Open Venation

Minor veins that terminate within the mesophyll without forming loops.

Major Veins

Large veins responsible primarily for structural support and long-distance transport.

Minor Veins

Smallest veins distributing water to and collecting sugars from photosynthetic cells.

Bundle Sheath

Layer of tightly packed cells surrounding a vascular bundle, regulating solute movement.

Bundle-Sheath Extension

Supportive tissue column linking bundle sheath to epidermis, adding rigidity (e.g., flax).

Collenchyma

Living support tissue with unevenly thickened walls, often reinforcing major veins.

Fibers

Thick-walled sclerenchyma cells providing additional mechanical strength to leaves.

Xerophyte

Plant adapted to arid environments, often with sunken stomata, thick cuticles, or hairs.

Leaf Crypt

Epidermal pocket containing stomata and hairs that reduces transpiration (e.g., Oleander).

Iridescence

Blue or metallic sheen produced by nanoscale cuticle striations, common in deep-shade species (e.g., Selaginella).

Transfusion Tissue

Parenchyma in conifer needles that laterally conducts water from xylem to mesophyll.

Endodermis (Leaf)

Inner boundary layer in some conifer leaves encircling vascular tissue; analogous to root endodermis.

Resin Duct

Canal lined with secretory cells that produce resin; characteristic of many conifers.

Interception of Light

Optical strategy where palisade cells act as light guides, maximizing chloroplast exposure.

CO₂ Diffusion Pathway

Air-space network in spongy mesophyll allowing rapid movement of carbon dioxide to palisade chloroplasts.

Lotus Effect

Super-hydrophobic property of some leaves where water beads and self-cleans the surface.

Determinate Growth (Leaf)

Developmental pattern where leaf growth ceases once the blade is fully formed, unlike indeterminate stems.