This lab deals with characters of the vegetative parts of a plant - roots, stems, twigs, and leaves.
Tap root--main root enlarging and growing downward
Fibrous roots--thin, thread-like roots, usually without a primary root present
Adventitious root--root growing from something other than root tissue, e.g. stem, etc.
Tuberous root---root enlarged for storage of food reserves
Aerial root--adventitious root produced above ground, often for climbing
Bud--A compressed, undeveloped shoot. Buds may be lateral or terminal.
Node--point on the stem where leaf or bud is borne. The space between two nodes is an internode
Leaf scar--mark left on the stem where a leaf was attached
Bud scale scar--mark on the stem where a bud scale was attached. When the 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.
Pith--the spongey tissue in the center of a stem or twig. Pith can be solid, chambered, or diaphragmmed.
Lenticel--a "breathing pore" in the skin or bark of a stem.
Tuber--underground stem enlarged for storage of food--has nodes (unlike tuberous root)
Rhizome--underground stem, often has buds which sprout to form new shoots (ferns, gingers)
Stolon--aboveground stem, has buds which sprout to form new shoots
Bulb--underground stem with fleshy leaves which store food, e.g. onion
Corm--fleshy underground stem with papery leaves, e.g. Gladiolus
Herb--no woody tissue
Shrub--woody, several stems from the base, less than about 25' tall
Tree--woody, usually one main stem, usually more than 25 ' tall
Vine--woody or herbaceous, stem climbing or twining
Petiole--the stalk of a leaf; a leaf without a petiole is sessile
Blade--the flat, expanded portion of the leaf
Stipule--flat, often leaf-like flap below a leaf. Not all leaves have stipules. Stipules can be highly modified into tendrils, spines, scales, etc. Do not confuse a stipule with the
Axillary bud--the bud in the axil--the angle between the leaf and the stem.
Helpful Hint: Remember to look for stipules below the petiole and an axillary bud above the petiole
Helpful Hint: In trying to decide where a leaf begins, look for the axillary bud. Everything above the axillary bud is all one leaf.
Simple--the 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.
Once pinnately compound--leaflets arranged along one undivided main axis.
Twice pinnately compound--main axis (rachis) with two or more branches 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.
Palmately compound--leaflets all arising from one point at the base of the leaf.
Alternate--leaves arranged one per node
Opposite--leaves arranged two per node
Whorled--arranged two or more per node
Fascicled--leaves grouped in small, tight bundles
Pinnate--with a main midvein and secondary veins arising from it at intervals
Palmate--with the main veins all arising from one point at the base of the leaf.
Parallel--with all the main veins parallel (usually also parallel to the sides of the leaf.)
Dichotomous--with each vein branching in two again and again (e.g. Ginkgo)
Pinnately lobed--with the lobes arising along the
length of the mid-line of the leaf.
Palmately lobed--with the lobes all arising from one point at the base of the leaf
There is a bewilderingly large number of terms used to describe the shapes of leaves (or of any other organ, for that matter). In this course, we will stress some of the more commonly-employed terms.
Awl-- small, spike-like leaves as seen in some
gymnosperms and lycopodiums
Cordate--heart-shaped with the wide part at the bottom FS
Deltoid -- triangular in shape
Elliptic--shaped like an ellipse, tapered at both ends and with curved sides.
Hastate--with two basal lobes that point straight out from petiole
Lanceolate--shaped like the tip of a lance, broadest at the base and tapered to a long point
Linear--very long and thin, with the sides parallel, as in grasses
Obcordate -- apical (tip) end has heart-like cleft
Oblanceolate -- shaped like the tip of a lance, narrowest at the base and broader towards the apical tip.
Oblong--tapered to both ends, but with the sides more or less parallel
Obovate -- Ovate with wider part towards apical tip
Orbicular--nearly circular in outline
Ovate--egg-shaped with the larger end at the bottom towards petiole
Palmate -- shape created when main veins arise from a single central point
Reniform -- kidney shaped
Peltate--with the petiole attached to the center of the underside of the blade
Perfoliate--with the petiole appearing to run through the center of the leaf
Sagittate--with two basal lobes that point backwards (toward the petiole)
Terete--circular in cross-section.
Helpful Hint: The prefix ob- means opposite, 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 long-tapered to the base.'
A number of terms describe the shape of the apex or base of a leaf. Some of the more common are:
Acute--forming an angle of less than 90 degrees
Acuminate--with a long, drawn-out taper (often with concave sides)
Cordate--shaped like the two lobes of a heart
Mucronate--with a tiny, usually stiff, point (mucro)
Obtuse--forming an angle of more than 90 degrees
Retuse--with a tiny notch taken out of the margin.
Rounded--just what you'd think
Truncate--cut straight across
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:
Entire--smooth, with no teeth or lobes
Dentate--with teeth which point outwards
Crenate--with low, rounded scallop-like teeth
Crisped--curled tightly (e.g. parsley)
Lobed -- having deep, regular, smooth, indentations that extend from the margin towards the main rib
Serrate--with sharp, forward-pointing teeth
Doubly serrate--with teeth which have smaller teeth on them
Serrulate --with very tiny sharp teeth
Sinuate -- with a sinusoidal (smooth wave) margin
Undulate--waving up and down
Plants can climb by one of several methods:
Twining--the stem wraps around an object for support (e.g. Morning Glory)
Tendrils--modified shoots, petioles, leaves or stipules coil around the support (e.g. Vetch)
Aerial roots---small roots, often with sucker-like tips (e.g. Virginia Creeper or Poison Ivy)
Plants can be armed in various ways:
Thorns--modified stems; have stem-like vasculature (e.g. Honey Locust)
Spines--modified leaves, stipules, or bud scales (e.g. Cactus)
Prickles--outgrowths of the epidermis, can be easily snapped off (e.g. Dewberry or Rose)
The above text was borrowed and modified from Texas A&M University:
The drawings were hand drawn by Dana Lee Ling in the Fall of 1999.
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