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Plant Morphology
Michael G. Simpson
Plant Structure Terms
Used for a specific structure/organ
Basic Plant Organs – Root + Shoot [Shoot = Stem + Leaves]
Both have terminal apical meristems
Plant Habit
= general form of a plant, encompassing stem duration and
branching pattern, development, or texture.
Herb - plant with annual above-ground parts (can be
annual or perennial)
Geophyte - perennial herb with rootstock
Vine - weak stemmed
Liana - woody vine
Shrub - woody, multiple stems from base
Subshrub - woody just above ground
Tree - woody, one trunk
Plant Duration
= how long a plant lives.
Annual- ≤ 1 year
Biennial- 2 years
Perennial- 3 or more years
Plant Habitat
= environment where plant lives.
Terrestrial – growing in soil
Aquatic
Submersed – totally surrounded by water
Floating – all or part of plant at surface
Emergent – rooted in water, arising above it.
Epiphytic – growing on another plant
Saxicolous – growing on or within rocks
Plant Life Form
= structure, life cycle, physiology.
Therophyte – annual
Geophyte – perennial herb
Epiphyte – plant growing on another plant
Halophyte – salt-adapted plants
Succulent – plant with fleshy leaves or stems
Xerophyte – plant living in dry, hot environments
Roots
Function - absorption, anchorage
Structure - rootcap, root hairs, endodermis
Adventitious roots - arise from non-root organ
Lateral roots - arise from another root (1˚, 2˚, etc.)
Roots:
-have a terminal apical meristem, producing cells
to the inside and outside (the latter -> rootcap)
Root Types/Parts
taproot
–primary root dominant
can form lateral roots
fibrous
–primary root withers,
subsequent roots adventitious
growing from stem
in a fibrous mass
aerial
–adventitious roots that generally do not enter the soil
and may absorb water and minerals from the air or
from runoff from plants
prop
–adventitious
roots help support
plant
haustorial
-roots parasitic,
penetrate tissue of
host plant
contractile
–roots that actually contract vertically, functioning to
pull the rootstock further into the soil
Root Types/Parts
storage roots
– taproot that has become greatly thickened, accumulating reservoirs of
high-energy storage compounds (usually starch)
E.g., Raphanus sativus, radish
Root Types/Parts
buttress roots
- enlarged, horizontally spreading and often vertically thickened roots at the base of trees
that aid in mechanical support, found in certain tropical or marsh/swamp tree species
E.g., Ficus rubiginosa, rusty-leaved fig
Root Types/Parts
pneumatophores
-roots that grow upward, out of soil (anti-geotropic),
function to absorb oxygen in anoxic soils
Avicennia germinans, black mangrove
Root Types/Parts
prop roots - are also adventitious
Shoot
= stem + associated leaves
Node:
point of attachment
of leaf/leaves
to stem
Internode:
region along stem
between
two nodes
Shoot:
stems and leaves are
intimately associated
early in development
Axillary/lateral buds:
develop into lateral branches,
can be vegetative or reproductive
(flowers, inflorescence)
Why is this a
single leaf?
Because the whole
structure develops
from a single leaf
primordium.
Caryota sp.
Arecaceae
leaf ca. 20 feet long!
Stem (Shoot) Types
areole
bulb
caudex
-modified, reduced,
-shoot consists of
-rootstock consists of
non-elongating
small amount ofvertical stem relatively undifferentiated
shoot apical meristem
(bearing roots below)
but vertically oriented
bearing leaf spines,
and a massive quantity
stem
characteristic of cactus family, of thick, fleshy
Cactaceae.
storage leaves
(e.g., Allium spp.,
onions)
May have bulbels (below)
bulbils (above)
caudiciform stem
-low, swollen, perennial
storage stem
(at or above ground
level), from which arise
annual or nonpersistent
photosynthetic shoots
(e.g., Calibanus, some
Dioscorea spp.)
rootstock – general term for underground stem, e.g., bulb, corm, rhizome, stolon
Stem (Shoot) Types
cladode
-flattened, photosynthetic
stem that may resemble
and function as a leaf,
found, e.g., in prickly-pear cacti,
Asparagus, and Ruscus.
corm
culm
-shoot consisting -the flowering
mostly of generally and fruiting
globose stem tissue
stem(s) of
surrounded by
grasses
scanty, scale-like
and sedges
leaves
(e.g., some Iris spp.)
fascicle/
short shoot
-modified shoot
with very short
internodes from
which flowers or
leaves are borne
rhizome
-horizontal
underground stem
(aboveground in some
ferns), typically with
short internodes,
bearing scale-like
leaves (e.g., ginger)
rootstock – general term for underground stem, e.g., bulb, corm, rhizome, stolon
Stem (Shoot) Types
scape
-a “naked” (lacking
vegetative leaves)
peduncle (inflorescence
axis), gen. arising from
a basal rosette
ofvegetative leaves,
functioning to elevate
flowers above the
ground.
stolon/runner
-a stem with long
internodes that runs
on or just below the
surface of the ground,
typically terminating
in a new plantlet, as
in Fragaria
(strawberry).
thorn
-a sharppointed stem
or shoot
tiller
tendril
tuber
-general term for
-a long,
-a thick,
proliferative grass
slender, underground storage
shoots, typically
coiling
stem, usually not
growing in masses
branch,
upright, typically
from axillary buds at adapted for bearing outer buds
the base of the stem
climbing
and lacking
surrounding storage
leaves or protective
scales (e.g., potato
rootstock – general term for underground stem, e.g., bulb, corm, rhizome, stolon
Stem (Shoot) Types
pachycaul
-woody, trunk-like stem, swollen basally, the swollen
region functioning in storage (e.g., bottle trees,
boojum tree)
pseudobulb
-a short, erect, aerial storage or propagative
stem of certain epiphytic orchids
Stem Habit
=relative position of stem (+ growth, structure)
prostrate
acaulescent
caulescent
cespitose
repent
arborescent
suffrutescent
decumbent
Stem Branching Pattern
sympodial
monopodial
dichotomous
sympodial
Twig Structure
collateral
pseudoterminal
naked
superposed
infrapetiolar
Leaf Structural Type
(Q 20-31; 100-117)
bractlets
bract
phyllode
scale
spine
tendril (leaf)
unifacial leaf
Leaf Structural Type
Bract (flower)
Epicalyx
Bud Scale
Leaf Structural Type
Phyllode - Acacia spp. (Fabaceae)
Leaf Structural Type
Tendril - Lathyrus (Fabaceae)
Leaf Structural Type
Stipular Spine - Euphorbia spp. (Euphorbiaceae)
Leaf Structural Type
Petiolar Spine - Fouquieria splendens Ocotillo (Fouquieriaceae)
Leaf Structural Type
Leaf Spine (arising from areole) - Cactaceae
Sharp things
thorn - sharp-pointed stem/shoot (fr. axillary bud)
spine - sharp-pointed leaf or leaf part
leaf spine (also leaflet spine)
stipular spine
petiolar spine
prickle - sharp pointed
epidermal appendage
Leaf Structural Type
Pitcher Leaf - Nepenthes (Nepenthac.) Sarracenia (Sarraceniac.)
Leaf Structural Type
Tentacular Leaf - Drosera spp Sundew (Droseraceae)
Leaf Structural Type
Trap Leaf - Dionaea muscipula Venus Fly Trap (Droseraceae)
Leaf Structural Type
Dionaea muscipula Venus Fly Trap (Droseraceae)
Leaf Structural Type
Iris sp.
unifacial
Seismonasty
Mimosa pudica Fabaceae
Leaf Type / Parts
imparipinnate
simple
pinnately
compound
paripinnate
bipinnately
compound
Leaf Type / Parts
palmate-ternate
pinnate-ternate
ternately compound
= trifoliolate
biternately
compound
palmately
compound
Leaf Type / Parts
geminate
unifoliolate
bigeminate
geminate-pinnate
costa-palmate
Leaf Attachment
petiolate
sessile
sheathing
decurrent amplexicaul
perfoliate
connateperfoliate
Leaf Venation
Leaf Venation