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Welcome to Northwest Plants
Northwest Indian
College
ENVS 201 Spring Quarter 2012
Plant Parts
reproductive
vegetative
organs: organs & structures:
stems
flowers
roots
fruits
leaves
seeds
Today:
Leaves
Leaf Features &
Functions
primary photosynthetic organs
may store food (in some species)
may shade neighboring competitor species
etc.
Leaf Components
blade (lamina)
petiole (or leaf stalk)
stomata & guard cells
trichomes (hairs; e.g., stinging nettle and
sundew)
bean (Phaseolus) leaf (a simple leaf)
lilac (Syringa) leaf, lower surface (showing stomata
and guard cells)
lilac (Syringa) trichome
Leaf Types
simple (a single blade; e.g., bean), or
compound (more than one blade; several
leaflets make up the compound leaf)
Compound Leaves
pinnate (or pinnately compound; with odd or
even number of leaflets; like a feather)
bipinnate (or bipinnately, or twice pinnately
compound)
palmate (or palmately compound; like the
palm of a hand)
ternate (or ternately compound; in 3s)
ash (Fraxinus) leaf (odd pinnately compound)
honey locust (Gleditsia) leaf (bipinnately compound)
horsechestnut (Aesculus) leaf (palmately compound)
clover (Trifolium) leaf (ternate)
Leaf Arrangement on Stem
alternate (one leaf per node)
opposite (two leaves per node)
whorled (three or more leaves per node)
paper birch (Betula), alternate leaf arrangement
highbush cranberry (Viburnum), opposite leaf arrangement
tobacco tree (Catalpa), whorled leaf arrangement
Leaf Venation
reticulate (or netted, or netlike); may be
palmate (e.g., maple) or pinnate (e.g., poplar)
parallel (e.g., grasses)
dichotomously branched (e.g., ferns and
ginkgo or maidenhair tree)
cleared leaf showing reticulate venation
maple (Acer) leaf (palmate venation)
chokecherry (Prunus) leaves (pinnate venation)
corn (Zea) leaves (parallel venation)
ginkgo (Ginkgo) leaf (dichotomously branched venation)
deer fern (Blechnum): a. free (some dichotomous) venation
in sterile pinna, b. netted venation of fertile pinna
Leaf Shapes
circular (circle-shaped)
heart (heart-shaped)
lanceolate (long and tapering)
linear (long, narrow, parallel sides)
etc.
Leaf Margins
entire (smooth)
wavy
serrate (with sharp teeth)
doubly serrate (larger teeth with smaller
teeth)
lobed (with lobes)
etc.
Leaf Tips
acute (tapering to a straight point)
obtuse (non-pointed, rounded)
aristate (with a stiff bristle tip)
cuspidate (with an abrupt, short, sharp rigid
tip)
etc.
Leaf Bases
truncate (cut off squarely)
sagittate (arrow-shaped)
stipulate (with stipules)
sessile (no petiole)
etc.
Leaf Surfaces
“top” (adaxial)
“bottom” (abaxial)
Surface Features
glabrous (smooth)
pubescent (with trichomes, hairy)
glandular (with glandular trichomes)
glaucous (with a waxy, whitish to bluish
coating)
etc.
Ecological Adaptations
xerophytes (plants adapted to arid
conditions, with accompanying leaf
adaptations; e.g., spines in cacti)
mesophytes (typical plants with typical
leaves)
hydrophytes (plants adapted to aquatic
conditions, with accompanying leaf
adaptations; e.g., leaf dimorphism)
Other Stuctures &
Modifications
bracts (leaflike structures)
tendrils (modified leaflets; also stipules,
petioles or stems)
spines (usually a modified leaf, leaf portion or
stipule; e.g., cacti; Opuntia also has glochids)
various modifications (e.g., insectivorous
plants)
bunchberry (Cornus) bracts (white)
pea (Lathyrus) tendril (modified leaflet)
cactus (Opuntia) spines and glochids (small
detachable hair-like spines) in areoles (highly
specialized branches of cacti)
Venus’ flytrap (Dionaea) traps
(with prey)
sundew (Drosera) (with sticky hairs)
butterwort (Pinguicula)
pitcher plant (Sarracenia)
bladderwort (Utricularia) with bladders
Questions &
Comments?
Leaves are cool.
Hy’shqe!