Lab 2: Vegetative Characters
|Objectives for this lab:
Safety concerns for this
lab: Be careful of plants with sharp parts, don't eat the
samples, and be careful where you step when walking on campus.
- learn the different root types
- learn to recognize and name different stem modifications
- learn to recognize and interpret simple and compound leaves
- become familiar with leaf shapes, bases, apices, margins,
arrangements, forms, and textures and the terms that describe these
- learn to recognize different growth forms--herbs, vines,
- learn to recognize vegetative features such as thorns,
spines, prickles, tendrils
- examine and learn to recognize different types of trichomes
- practice keying with a key that uses vegetative characters
This lab deals with characters of the vegetative parts of a
stems, twigs, and leaves.
Most items have a visual link, but some do not. This topic is covered
in Vascular Plant Taxonomy by Walters and Keil .
root--main root enlarging and growing downward
roots--thin, thread-like roots, usually without a primary
Adventitious root--root growing from
other than root tissue, e.g. stem, etc.
Tuberous root---root enlarged for storage
of food reserves, eg. sweet
root--adventitious root produced above ground, often for
compressed, undeveloped shoot. Buds may be lateral or terminal.
on the stem where leaf or bud is borne. The space between two nodes is
scar--mark left on the stem where a leaf was attached
scale scar--mark on the stem where a bud scale was attached.
terminal bud sprouts and its scales fall off, growth rings are formed.
The portion of a stem between two sets of
growth rings indicates one season's growth.
spongey tissue in the center of a stem or twig. Pith can be solid,
"breathing pore" in the skin or bark of a stem.
stem enlarged for storage of food--has nodes (unlike tuberous root)
stem, often has buds which sprout to form new shoots
stem, has buds which sprout to form new shoots
Bulb--underground stem with fleshy leaves
which store food, e.g. onion
Corm--solid, fleshy underground stem with
papery leaves, e.g. Gladiolus,
several stems from the base, less than about 25' tall
usually one main stem, usually more than 25 ' tall
or herbaceous, stem climbing or twining
Annual--plant which lives for one year or
season, reproduces, and then dies
Biennial--plant which lives for two years
or seasons, reproduces, and then dies
Perennial--plant which lives for several to
many years or seasons. Perennials may be woody, with stems that persist
aboveground over the winter, or they may be herbaceous, with stems that
die back to the ground each year.
Evergreen-having leaves which persist for
two or more seasons. Broadleaf evergreens usually have thick, leathery
Deciduous--having leaves which die and fall
in the cold or the dry season.
PARTS OF A LEAF and NODE
stalk of a leaf; a leaf without a petiole is sessile
flat, expanded portion of the leaf
often leaf-like flap below a leaf. Not all leaves have
Stipules can be highly modified into tendrils, spines, scales, etc. Do
not confuse a stipule with the
bud--the bud in the axil--the angle between the leaf and the
Remember to look for stipules below the petiole and an
axillary bud above
arranged one per node
arranged two per node
two or more per node
grouped in small, tight bundles, eg., pine needles bundled into
clusters of 2 or 3
SIMPLE AND COMPOUND LEAVES
Hint: In trying to decide where a
begins, look for the axillary bud. Everything above the
bud is all one leaf.
blade is all in one piece, though it may be lobed, toothed, etc.
Compound--the blade is divided all the
way to the midrib (rachis) into two or more pieces.
pinnately compound--leaflets arranged along one undivided
A leaf is even pinnately compound (paripinnate) if the leaflets
are in pairs with none left over (as in the linked image.) A leaf
is odd pinnately compound (imparipinnate) if the leaflets are
all in pairs except one left over at the tip.
pinnately compound--main axis (rachis) with two or
and the leaflets arranged along the branches. The branch divisions are primary
leaflets and the ultimate divisions are secondary leaflets.
There can also be thrice-pinnately compound leaves,etc.
compound--leaflets all arising from one point at the
a main midvein and secondary veins arising from it at intervals
the main veins all arising from one point at the base of the leaf.
all the main veins parallel (usually also parallel to the sides of the
each vein branching in two again and again (e.g. Ginkgo)
lobed--with the lobes arising along the length of the mid-line of the
lobed--with the lobes all arising from one point at the base of the
There is a bewilderingly large number of terms used to describe the
of leaves (or of any other organ, for that matter). In this course, we
will stress some of the more commonly-employed terms.
with the larger end at the bottom
The prefix ob- means
so for every shape term, a term for the same shape turned the other way
around can be created by adding "ob-" to the term. For example, oblanceolate
means 'shaped like the tip of lance, broadest at the top and
to the base.'
like an ellipse, tapered at both ends and with curved sides.
to both ends, but with the sides more or less parallel
like the tip of a lance, broadest at the base and tapered to a long
long and thin, with the sides parallel (In this photo, the grass-like
are linear; they belong to the pink-flowered plant)
circular in outline
with the wide part at the bottom
two basal lobes that point straight out
two basal lobes that point backwards (toward the petiole)
the petiole attached to the center of the underside of the blade
the petiole appearing to run through the center of the leaf
in cross-section. (The example shown is from a succulent
APICES AND BASES
A number of terms describe the shape of the apex or base of a leaf.
of the more common are:
an angle of less than 90 degrees
an angle of more than 90
degrees. (In this image, the terminal lobe of each 3-lobed leaf is
a long, drawn-out taper (often with concave sides)
what you'd think
like the two lobes of a heart
a tiny, usually stiff, point (mucro)
Truncate--cut straight across
a tiny notch taken out of the margin.
the two halves of the base not equal
in size or not meeting the petiole at the same point.
leaf is decurrent if its tissue runs down the stem from the point of
attachment. This is usually in the form of thin wings
There is an astounding number of terms used to describe the margin of a
leaf (or any other structure.) Some of the more common are:
Plants can climb by one of several methods:
stem wraps around an object for support (e.g. Morning Glory)
shoots, petioles, leaves or stipules coil around the support (e.g.
roots---small roots, often with sucker-like tips (e.g.
or Poison Ivy)
Plants can be armed in various ways:
stems; have stem-like vasculature (e.g. Honey Locust)
leaves, stipules, or bud scales (e.g. Cactus)
of the epidermis, can be easily snapped off (e.g. Dewberry or Rose)
Succulent--swollen and juicy. Eg., cactus
of some plants. Here is an extreme
example of succulent leaves.
and leaf-like. (May be applied to many different sorts of parts,
such as sepals, etc.)
and flexible, like a membrane. (In this photo, the bracts below the
dry, and somewhat transparent or scaly, often yellowish, whitish, or
brownish in color rather than green
and TERMS TO DESCRIBE SURFACES
Plants can be glabrous
(without hairs) or may have various sorts of hairs. There are
many terms used to describe the hairs or the surface. Here are a
CLICK HERE FOR THE PICK-TEN
QUIZ OVER VEGETATIVE MORPHOLOGY
-- straight and unbranched
--shaped like stars. The rays may be free or fused
with a gland
or swollen and gland-like. You may also
stalked glands--glands with stalks stiffer than hairs
--the main hair has side branches (look at the hairs on
midrib of the leaf)
hair or bristle--the main hair has side hairs (the smaller side hairs
are just visible on each big hair)
thin, flat structure (like a fish scale), often attached in the center
and with a coating of wax
short hairs around the margin
long, soft, spreading hairs. Here is another
short, soft hairs (This term is sometimes incorrectly used to
refer to having hairs of any sort)
stiff, spreading hairs. Here is another
(look at the hairs along the veins)
rather stiff, appressed hairs
or sandpapery, with very
short, stiff hairs or projections (Examine the close up shots of the
leaves and stem)
a dense, soft coat of hairs
that is hard to see through, e.g., underside of mustang grape leaves
long, tangled, cobweb-like hairs
covered with scattered glands. These usually look greasy, or like
little drops of yellow or dark oil. Glandular
scattered glands in the bottoms of little pits. (Look at the surface of
the whitish bracts below the flowers)
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last updated 25
June, 2010 by MDR