Basic Botany
All living things grow and reproduce; in order to do so, each organism needs
food for energy. Unlike animals, plants cannot get their food by eating other
organisms. Instead, plants produce their own food, using raw materials from
the air and soil, with the help of energy from sunlight. Plants are essentially
factories for the production of food from simple raw materials; without plants
there would be no food for all of the other living organisms on the planet.
All of the seed-bearing plants share certain similarities--that is, they are constructed from similar basic
parts, and grow and function in certain basic ways. It is important to understand these underlying
similarities so that the infinite variations on the theme can be put into perspective.
All plants consist of three major organs: roots and shoots are the vegetative organs of a plant. They are
responsible for keeping the food-producing "factory" running. Flowers are the reproductive organs of a
plant.
Roots
Roots are the major underground organ of a plant, and provide the following functions:
 anchorage for the plant in the soil.
 absorption of water and dissolved minerals (i.e., the raw materials) from the soil by tiny "root hairs"
along the outer roots.
 storage of excess foods for later use.
Some of the more interesting modified or specialized root adaptations include:
 tuberous roots
swollen, enlarged roots whose
function is to store food and water
during unfavorable growing
conditions.
 adventitious roots
 prop and stilt roots
 root buttresses
roots originating from some
other parts of the plant, such as
the stem or leaf (e.g., roots
from cuttings for propagation).
special adventitious roots which
develop from above-ground sterns
to help support a particularly tall or
wide-spreading plant.
special outgrowths of the upper
roots or lower trunk of tall tropical
trees to provide additional support
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in shallow soils.
 aerial roots
roots that develop on epiphytic and
vining plants in moist forests to help
anchor plants and absorb moisture
from the air.
Shoots
Shoots actually consist of two parts--stem and leaf--but develop as one unit as the plant grows. The
stem portion of a plant has several functions:
 support the plant above ground.
 display the leaves at the correct angle.
 conduct water and minerals from the root upward and food from the leaves downwards.
 store water and excess foods.
The leaf contains most of the chlorophyll and is therefore the major place where the food is produced.
Leaves produce food in the form of sugars from carbon dioxide and water, through a process called
photosynthesis. Leaves are also the area where most water loss occurs.
A mature shoot consists of the terminal bud at its tip, and below that a stem with
leaves. Each leaf is attached to the stem at a node; an axillary bud will be found just
above (in the axil of) the leaf. Each axillary bud has the potential of becoming a new
shoot system, or side branch, but not every bud does so. The basic branching
pattern of each kind of plant depends upon how many of the axillary buds do grow
into branches.
The stem portion of the shoot system is frequently modified or adapted to special situations:
 corms, tubers, and rhizomes: specialized underground stems which store food and water
during periods unfavorable for growth.
 stolons, rootstocks, and runners: specialized stems near the soil surface whose function is to
start new plantlets by vegetative means.
 photosynthetic stems: green stems which function in place of leaves on desert plants such as
cacti.
 pseudobulbs: special water-storing stems on epiphytic orchids.
 prickles: spiny outgrowths of stems (e.g., roses).
 thorns: sharply pointed stems modified for protection, as on Euphorbia.
Leaves
A leaf may consist of one or more parts:
 the blade: the thin, flattened part where photosynthesis takes place.
 the petiole: a stem-like portion connecting the blade to the shoot (some leaves do not have
this).
 the stipules: pairs of small leafy structures at the base of the petiole (many leaves do not
have these).
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Leaves vary tremendously as to size, arrangement, shape, and details of texture and color. Leaf details
can therefore be helpful in plant identification, although it should be noted that many leaf features
may be adaptations to certain environmental conditions and that therefore, leaves with similar
features do not indicate a relationship. In other words, totally unrelated plants adapted to the same
specialized environment may have leaves which look very much alike. Some useful leaf terms are
illustrated on the Leaf Identification Key. Other terms are listed below.
Leaf Arrangement
alternate: one leaf per node
opposite: two leaves per node
whorled: three or more leaves per node
Leaf Form
simple: leaves whose blades are in one continuous
piece
compound: leaves whose blades are divided into
separate parts called leaflets (leaves will always have
a bud at their base; leaflets will not)
Leaf Texture/Color
glabrous: smooth, without hairs
pubescent: hairy or fuzzy (there are many other specialized terms
for the hairs on a leaf)
glaucous: covered with a whitish, grayish, or bluish powder
In addition, leaves may sometimes be further specialized:
 windowed leaves: have transparent areas for letting light in so the rest of the leaf may be
buried to reduce water loss (e.g., desert succulents).
 leaves with drip tips: tips are tapered and channeled to allow water to run off the ends
(necessary in tropical trees where rainfall can be excessive).
 succulent leaves: fleshy, water-storing leaves.
 insectivorous leaves: leaves modified into traps to catch insects (such plants live in nitrogenpoor soils and supplement with animal proteins).
 needle leaves: very narrow, stiff, sharply pointed leaves.
 tendrils: curly, twining structures which wind around objects for support on vining plants.
 spines: leaves modified into sharp, non-green structures to protect the plant.
Flowers
Flowers are the reproductive organs of a plant. Their sole purpose, as far as the plant is concerned, is
to produce seeds, which will in turn develop into new plants. A flower is actually made up of several
very specialized leaves and stems whose form and arrangement allow the proper development and
dispersal of the seeds.
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Seeds, like the babies of animals, can usually only be produced when the egg cells of the female are
fertilized by the male cells of another flower. This process of fertilization in plants is the result of
pollination of the flowers. Pollination is the transferring of pollen (the male cell) from one flower to
the female pistil of another flower of the same kind.
There are a seemingly infinite number of combinations of flower form, color and arrangement, but
each combination merely represents a different strategy in guaranteeing that pollination, fertilization,
seed production and dispersal will take place so that more plants can be produced. There is, however,
a basic pattern in the form of a flower, with parts designed to serve very specific functions in the
process of reproduction.
The five basic parts are:
 the receptacle: the enlarged end of a shoot to which some or all of the other flower parts are
attached.
 the sepals: the outer layer of modified leaves, often green and tough, whose purpose is to
protect the other parts of the flower.
 the petals: an inner layer of modified leaves, often brightly colored or distinctively marked,
which provide a banner to attract pollinators to the flower.
 the stamens: the pollen-producing male part of the flower.
 the pistil: the female part of the flower containing the eggs which will grow into seeds upon
fertilization.
All of the sepals together make up the calyx: all of the petals make up the corolla. The calyx and the
corolla combined make the perianth. A "complete" flower will have all five of the flower parts. A
"perfect" flower will have both male and female parts but may lack the perianth. Some flowers may
have only stamens or only a pistil; these will be called "staminate" or "pistillate" flowers. The actual
numbers of each flower part present will vary tremendously; the unique combinations and numbers of
these parts can be used to identify different plants.
While the petals may provide the most attractive aspects of a flower from our human viewpoint, the
most important parts from the view of reproduction are the stamens and pistil--the male and female
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parts of the flower. The stamen consists of two parts: the long, slender filament and the pollenproducing anther at its tip. The pistil likewise has several parts to it: the sticky-surfaced stigma for
receiving pollen, the slender stalk of the style, and the egg-filled ovary at the base. There are usually
many stamens in a flower but often only one pistil. Each is designed so that a pollinator (insect or bird,
usually) will have no difficulty transferring pollen from one flower to another.
The arrangement of flowers is called the inflorescence. There are again a great number of different
patterns in the inflorescence of each plant. They will vary from single flowers to hundreds of flowers
each, and from very tight, uniform clusters to open, irregular arrangements of flowers.
Seeds
A seed is a miniature plant wrapped up in a protective package. Each “embryonic” plant will have
roots, stems and leaves ready to grow into a new plant just like the mother plant. Enough food is
stored within the seed to allow for the growth of the new plant until it can begin producing its own
food. This growth will commence when there is the right combination of moisture, light and
temperature.
The seeds are produced inside the ovary of the mother plant, following fertilization of the eggs or
ovules. As the seeds begin to develop, changes take place in the ovary: it will begin to enlarge and,
sometimes in combination with the receptacle, will develop into a protective container for the seeds.
This container is called a fruit. The first purpose of the fruit is to protect the seeds inside as they are
developing. The fruit may also provide a means for dispersing the seeds away from the mother plant,
so that the seedlings will not have to compete with their parent for the raw materials they need from
the soil, nor for the sunlight they need for photosynthesis to take place.
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