lbbbion exam 3 [the leaf]

leaf

another plant organ that, along with stems, constitutes the shoot of the plant body and its principal function is to act as the main site of photosynthesis in a plant. 

blade

a flattened laminar portion of the leaf

petiole

a stalk on the leaf which attaches the blade to the stem

stipules

small leaf-like structures which develop in pairs on each side of the leaf during the growing season

midrib

blade or lamina is lined with the veins; the middle portion of the blade usually has a prominent central vein

netted venation

arrangement of veins in dicots

parallel venation

arrangement of veins in monocot

margin

also known as the edge of the blade

apex

also known as leaf tip

simple

type of leaf that has a single blade or lamina

compound

type of leaf that is composed of two or more separate leaflets.

epidermis

outermost layer of cells and secrete a waxy substance which forms a covering over the outer dermal cells rendering these cells impermeable to water.

cuticle

waxy covering

stomates

openings in the epidermis

guard cells

specialized epidermal cells

palisade layer

the cells toward the upper epidermis, which are elongated

spongy layer

the zone below the palisade layer, composed of irregularly shaped cells