BOTANY L6: Leaves

Abaxial Side

lower side of a leaf blade

Adaxial Side

upper left side of a leaf blade

Compound leaf

leaf divided into several individual parts (leaflets)

Cylinder stem

efficient for support and transport but inefficient for photosynthesis

Foliage leaves

main photosynthetic organs of most plants

Lamina

another term for leaf blade

Rachis

central axis of a compound leaf bearing the leaflets

Shoot system

contains both the stem and leaves

Leaves

flat and thin for maximum absorption of light and carbon dioxide

Stems

elevate leaves and conduct material to and from them

Photosynthesis

the most obvious function of foliage leaves

Leaf blade

flat, light-harvesting portion

Petiole

holds the blade out into the light

Sessile leaf

leaf with no petiole

Aeronium

grows in arid, sunny regions, and its fleshy leaves are packed together

Sheathing leaf base

the leaf base wraps around the stem to form this

Simple leaf

a leaf that has a blade of just one part

Compound leaf

leaf with a blade divided into several individual parts

Leaflets

small leaf blades from a compound leaf

Veins

bundles of vascular tissues

Veins

distribute water from the stem into the leaf and simultaneously collect sugars

Reticulate venation

veins in basal angiosperms and eudicots that occur in a netted pattern

Parallel venation

in monocots with long, strap-shaped leaves, the larger veins run side by side with a few obvious interconnections

Abscission zone

in the leaf base; its cells are involved in cutting off the leaf when its useful life is over

Leaf scar

adjacent undamaged cell that become corky and form a protective scar tissue called ___ across the wound

Transpiration

water loss through the epidermis

Leaf stomata

frequently sunken unto epidermal cavities that create a small region of nonmoving air

Leaf epidermis

often remarkably hairy

Trichomes

deflects excessive sunlight and prevent rapid air movement

Leaf epidermal cells

contain a coating of cutin and wax on their outer walls

Mesophyll

ground tissues interior to the leaf epidermis

Palisade Parenchyma

main photosynthetic tissue of most plants

Palisade cells

separated slightly so each cell has most of its surface exposed to intercellular spaces

Spongy mesophyll

permits carbon dioxide to diffuse rapidly away from stomata into all parts of the leaf’s interior

Midbrib

also called midvein

Lateral veins

emerge from midrib that branch into narrow veins

Minor veins

most important for releasing water from xylem and loading sugar into phloem

Bundle sheath

fibers arranged as a sheath to support the leaf blade

Minor veins

the site of material exchange with the rest of the mesophyll

Bundle sheath extension

mass of fibers that help give rigidity to the blade

Petiole

the transition between the stem and the lamina

Leaf traces

multiple vascular bundles that branch from stem vascular bundles

Stipules

two small flaps of the petiole’s tissue that protects the shoot apical meristem

Leaf primordium

cells interior to the protoderm that grow outward, forming a protrusion

Perennial plants

plants where leaves are initiated in the summer or autumn before they mature

Monocot leaves

initiated by the expansion of some shoot apical meristem ti firm a leaf primordium

Apical meristem cells

cells that grow upward along the primordium until it completely encircles the shoot apical meristem

Succulent leaves

thick and fleshy for water conservation

Lithops

stone plants