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BOTANY BASICS
David Shibles
Master Gardener Coordinator
Polk County Cooperative Extension
Adapted from Botany Basics by Dr. Ann Marie
VanDerZanden, Extension Master Gardener
Coordinator, Oregon State University
THE PLANT WORLD
The plant world is extremely diverse,
ranging from one celled algae to huge oaks
and sequoias.
It contains plants like mushrooms which have
no green color.
In our gardens we find lichens and mosses,
which are green plants, but have no true
roots, no leaves and no flowers.
Many of us grow ferns in our gardens. They
are green plants with true leaves and roots,
but no flowers.
Finally there are the flowering or seed
bearing plants, which make up the vast
majority of plants on earth. These are the
plants that we wish to discuss today.
SEED PLANTS-Spermatophyta
The seed plants are those which produce
seeds, each containing an embryo (a
minute, inactive plant) that germinates
(begins to grow) under favorable
conditions.
Seed bearing plants have true leaves,
stems, roots and vascular tissue.
They consist of two classes-the
Gymnospermae and Angiospermae
Gymnospermae-gymnosperms
All gymnosperms are woody, perennial, and
with few exceptions evergreen. The
reproductive organs are borne in structures
called catkins or in cones.
Their leaves may be fern-like, scale-like,
strap-shaped, or needle shaped. This group
is represented primarily by cone bearing
trees (conifers) and palm-like plants called
cycads.
Members of this group are cypress, cycads,
ginkgo, pine and cedars, podocarpus, yews
and torreya.
Angiospermae
The angiosperms include those groups which
have flowers and seeds always protected by
a fruit.
They are broken down into two main groups
the Monocotyledoncae and the
Dicotyledoncae.
These divisions are determined by the
number of cotyledons or “seed leaves” found
in the seed.
MONOCOTS
1. Have one seed leaf.
2. Xylem and phloem are paired in bundles
and are dispersed throughout the stem.
3. The floral parts are usually in multiples
of three.
4. The leaves often have parallel veins.
DICOTS
1. Have two seed leaves.
2. The xylem and phloem are inside the stem.
The ring of phloem is near the bark; the
xylem forms the inner ring.
3. The floral parts are usually in multiples of
four or five.
4. The leaves are usually net veined.
PLANT LIFE CYCLES
1. Annuals-completes its full life cycle in one
year. Winter and summer annuals. Summer
annuals include many flowers, crabgrass and
spurge. Winter annuals include annual bluegrass and henbit.
2. Biennials-produce vegetative the first
year, then produces seed the seconds year.
Examples are Swiss chard, carrots, beets.
Weeds include cudweed and bull thistle.
3. PERENNIALS - plants that live 2 years or
more and are divided into herbaceous and
woody perennials.
- Herbaceous perennials have soft nonwoody
stems that generally die back to the ground
each winter if the temperature is cold enough
and new stems grow from the plants crown in
the spring. Or they may just keep on growing.
- Woody perennials have woody stems that can
withstand cold winter temperatures and include
shrubs and trees.
PERENNIALS (con’t)
INTERNAL PLANT PARTS
Cells are the basic unit of plants. Plant reactions
such as cell division, photosynthesis, respiration
go on at the cellular level.
Plant tissues such as meristems, xylem and
phloem are large organized groups of cells that
work together to perform specific functions.
A unique feature of plant cells is that they are
totipotent
Specialized groups of cells called meristems
are the plants growing points.
EXTERNAL PLANT PARTS
Leaves, stems, roots, flowers, fruits, and seeds
are known as organs. They can be divided into
sexual reproductive and vegetative.
Sexual reproductive parts produce seed. They
include flower buds, flowers, fruit and seed.
Vegetative parts include roots, stems, shoot buds,
and leaves. They are not directly involved with
sexual reproduction.
Vegetative parts can be used in asexual forms of
reproduction such as cutting, budding and
grafting.
External Plant Parts-roots
Their principle functions are to absorb
nutrients and moisture, anchor the plant,
support the stem, and store food. They can be
used for propagation in some plants. The
meristematic zone manufactures new cells.
zone of elongation cells increase in size and
push the root through
the soil.
zone of maturation cells become specific
tissues-epidermis,
cortex, or vascular
tissue.
Epidermis-outermost layer which absorbs water
and nutrients.
Cortex cells help move water to vascular tissue
and storing food.
Root cap protects the end of the root.
Root hairs are epidermal cells that occur in a
small zone behind the root’s growing tip. They
increase the absorptive capacity of the root. They
usually live one or two days.
Roots often have a symbiotic relationship with
certain fungi - mycorrhizae (fungus + root).
Types of roots
1. Primary or taproot-if the primary root
elongates downward and develops few lateral
roots then it is called a taproot. Examples are
hickory and pecan trees and carrots.
2. Lateral root-is a side or branch root that arises
from another root. If the taproot ceases to
grow then a fibrous root system forms.
How do roots grow - fertility, moisture and
air spaces.
Factors Important For Good Root Growth 1. Roots in water saturated soil may die from
lack of oxygen.
2. Roots penetrate much deeper in loose, well
drained soil, than in heavy, poorly drained
soil.
3. A dense compacted soil can restrict or
terminate growth.
4. Container plants have a restricted area for
growth and the roots may be more sensitive
to cold damage.
5. Keep in mind that plants grow downward
as well as laterally.
Vascular System-consists of xylem, phloem,
and vascular cambium.
Xylem-conduct water and dissolved minerals.
Phloem-carries food such as sugars.
Cambium-is a layer of meristematic tissue that
separates the xylem and phloem and produces new
xylem and phloem cells.
The vascular cambium
is important in grafting,
because they need to line
up or the graft will fail.
Dicots-the vascular system is said to be continuous
because it forms rings inside the stem.
The ring of phloem is near the bark and eventually
becomes part of the bark.
The xylem forms the inner ring and is often called
the sapwood and heartwood.
This is important to the gardener because herbicides
like 2,4-D kill only dicots.
Roots As Food An enlarged root is the edible portion of several
vegetables. Sweet potatoes are a swollen tuberous
root: carrots, parsnips, salsify, and radishes are
elongated taproots.
STEMS
Support buds and leaves and act as a
conduit for carrying water, minerals, and food
from photosynthesis. They may be above or below
ground.
The vascular system inside the stem forms a
continuous pathway from the roots to the leaves.
Stems may be long with great distances between
leaves and buds (branches of trees) or they may
compressed like crowns of strawberry plants,
fruit spurs and African violets.
Above ground stems-crowns, spurs or stolons
Crowns are compressed stems with leaves and
flowers on short internodes (strawberries,
dandelions, and African violets).
Spurs are short, stubby side stems that arise
from a main stem. They are the fruit bearing
stems on pears, apple, cherry trees, etc.
Do not do severe pruning close to fruit-bearing
spurs, because the spurs can revert back to
vegetative stems.
Stolons are fleshy or semi-woody, elongated,
horizontal stems that often lie on the soil surface.
Leaves and roots develop from the nodes (spider
plants, St. Augustinegrass and strawberries).
Under-ground stems
Potato tubers, iris rhizomes, and tulip bulbs
are underground stems that store food for the
plant.
It is sometimes difficult to distinguish between
roots and underground stems, but one sure way
is to look for nodes. Stems have nodes; roots
do not.
Below ground stems-tubers (potatoes)
The eyes in potato tubers are
actually nodes, and each eye
has a cluster of buds.
When growing potatoes from
seed pieces, it is important
that each piece contain at least
one eye and be about the size of
a golf ball
Below ground stems -
Rhizomes resemble stolons because they grow
horizontally from plant to plant. Some are fleshy
compressed (iris), while others are slender and
have long internodes (bentgrass).
Johnsongrass is a particularly bad rhizomonous
weed.
Tulips, lilies, and onions produce bulbs, which
are shortened, compressed underground stems
surrounded by fleshy scales (leaves) that envelop
a central bud at the tip of the stem.
After a bulb-producing plant flowers, its phloem
transports food reserves from its leaves to the
bulb’s scale. When the bulb begins growing in
the spring, it utilizes the stored food. So don’t cut
the old leaves off until they have withered and died.
Bulbs are classified as tunicate and non-tunicate
bulbs.
Tunicate bulbs have a thin papery covering
which is actually a modified leaf (narcissus, daffodils
amaryllyis, tulips and onions). This helps protect
the bulb from drying out and mechanical damage.
Non-tunicate bulbs (various lilies) do not have
the papery covering. They have to handled with
care.
Corms are another kind
of below ground stem.
Bulbs and corms are
composed of the same
tissue, but they are not
the same.
A corm is a solid mass of stem tissue with a
terminal bud on top. In additional to the terminal
bud, axillary buds are produced at nodes.
It is protected against injury and water loss by dry
leaf bases similar to the tunic in true bulbs
(gladiolus, Watsonia, Tritonia, Freesia,
and African lily).
Some plants produce a modified stem called a
tuberous stem (tuberous begonia and cyclamen).
These stems are short, flat, and enlarged. Buds
and shoots arise from the crown, and fibrous
roots grow from the bottom.
Other plants (dahlias and sweet potatoes) produce
underground storage organs called tuberous roots.
These are often confused with bulbs and tubers,
however, these are root tissue and not stem tissue.
They do not have nodes or internodes.
Stems and Propagation Aboveground stems with nodes and internodes
can be used to create new plants.
Below-ground stems are also good propagative
tissue. Rhizomes can be divided into pieces,
bulblets or cormels can be removed from the
parent, and tubers can be cut into pieces
containing eyes.
Types of plants and their stems Trees have one or two main trunks and are usually
taller than 12 feet while shrubs have many main
stems and are usually less than 12 feet tall. Both
have large amounts of hardened xylem in the core.
Herbaceous or succulent stems contain lessor
amounts of sapwood - may only live a year and
re-grow from the crown.
Canes are stems with relatively large pith. They
live only 1-2 years (roses, grapes, blackberries,
and raspberries). For fruit production it is good to
know which canes to prune.
Vines-have long trailing stems.
Some vines grow along the ground while others
need a structure to grow on. Twining vines circle
a structure for support.
Some circle clockwise (hops and honeysuckle),
while other circle counterclockwise (pole beans
and Dutchman’s pipe).
Climbing vines are supported by either aerial
roots (English ivy and poison ivy), by slender
tendrils that encircle an object (cucumber,
gourds, grapes, and passion flower), or by tendrils
with adhesive tips (Virginia and Japanese creeper).
Stems as food-The edible portion of several plants,
such as kohlrabi, is an enlarged edible, succulent
stem.
The edible parts of broccoli are composed of stem
tissue, flower buds, and a few small leaves.
The edible part of a potato is a fleshy underground
stem.
The edible part of cauliflower is actually
proliferated stem tissue.
Buds-A bud is an undeveloped shoot from which
leaves or flower parts grow.
Buds of many plants require a cold period before
they start to grow in the spring-central Florida
peaches require 250 hours (chill units) below
45 degrees).
A leaf bud is composed of a short stem with
embryonic leaves. Leaf buds are often less plump
and more pointed than flower buds.
Terminal buds are located at the apex of a stem.
Lateral (auxillary) buds are located on the sides
of a stem and usually arise where a leaf meets a
stem (an axil).
Adventitous buds arise at sites other than the
terminal or axil, such as roots, stem internode,
edge of a leaf blade, or callus tissue at the end of
a stem or root.
Buds as food
Cabbage and head lettuce are unusually large
terminal buds.
Succulent axillary buds are the edible parts
of Brussels sprouts.
The fleshy basal part of the flower bud’s bract
is eaten in globe artichoke along with the stem.
Broccoli is probably the most important crop
in Horticulture as the flower bud is eaten along
with the stem and small leaves.
Leaves
Function and structure
The main function of
the leaf is to absorb
sunlight to manufacture
plant sugars through
photosynthesis.
A leaf is held away from the
stem by a petiole and it is
attached to the stem at a
node. Where they meet is a
leaf axil which contains a
bud or buds.
Some leaves have hair-like
extensions called pubescence.
The cuticle is part of the epidermis and produces
a waxy layer called cutin which protects the leaf
from diseases and dehydration.
x
Guard cells regulate
the passage of
CO2, O2 and water
through tiny openings
called stomata.
Types of leaves
Scale leaves-are found on rhizomes and buds,
which they enclose and protect.
Seed leaves-(cotyledons) on embryonic plants.
They store food for the developing seedling.
Spines and tendrils-such as those found on
barberry and pea plants, protect a plant or help
support its stems.
Storage leaves-on bulbous and succulent plants.
Bracts-brightly colored (dogwoods and poinsettias).
Leaf venation-monocots.
Parallel veined-mostly grasses (monocots) where
the veins run essentially parallel to each other,
(base to apex) except such plants as banana, calla
and pickerel-weed, whose veins run laterally from
the midrib.
Leaf venation-dicots
Pinnate veins-veins extend laterally from the
mid-rib to the edge (apple, cherry and peach).
Palmate veins-principle veins extend outward,
like the ribs of a fan (grapes and maples).
Leaves shape and plant identification
lanceolate-longer than wide,
tapering toward apex/base
linear-several times longer
than wide-same width
cordate-heart shaped-turns
in an forms a notch where
petiole is attached
ellipitical-2-3 x as long as
wide-tapers to acute or
rounded apex at base
ovate-egg shaped
Leaf edges
entire-smooth edge
crenate-rounded teeth
dentate-teeth ending in an
acute angle pointing outward
serrate-small sharp teeth
pointing toward the apex
incised-cut into sharp
deep,irregular teeth
lobed-incisions extending
less than half way to
midrib
Leaf base shapes
Cuneate-wedge shaped; triangular with the narrow
end at the point of attachment.
Obtuse-tapering to a rounded point.
Cordate- turning in and forming a notch
Leaf apex shapes
Acute-ending in an acute angle, with a sharp,
but not acuminate point.
Accuminate-tapering to a long narrow point.
Obtuse-tapering to a rounded edge.
Simple leaves-the leaf blade is single continuous unit.
Compound leaves-are composed of several separate
leaflets arising from the same petiole. Some leaves
are doubly compound.
opposite-leaves are position across from each other.
alternate-leaves are arranged in alternate steps along
the stem, with only one leaf at each node.
whorled-leaves are arranged in a circles along the
stem.
rosulate-leaves arranged in a rosette around the stem,
with extremely short internodes.
Leaves as food-the leaf blade is the principal edible
part of several horticultural crops, including chives,
collards, dandelions, endives, kale, mustard, parsley,
spinach, Swiss chard and other greens.
The edible part of leeks, onions and Florence fennel
is a cluster of fleshy leaf bases.
The petiole is the edible product in celery and
rhubarb.
Flower Structure
Collectively the sepals
are called the calyx.
Petals may contain
perfume-collectively the
petals are called the
corolla.
The flower is very important for plant identification.
Flowers of dicots typically have 4-5 sepals and or petals.
Monocots typically come in 3’s or multiple of 3’s.
Types of flowers
If a flower has a stamen, pistil, petals and sepals,
it is called a complete flower. If one of these
parts is missing, then it is called an incomplete
flower.
The stamen and pistal are the essential parts of
a flower for seed production. If it contains both
stamens and pistal, then it is called a perfect
flower.
If either the pital or stamen is missing, then it is
called imperfect pistillate or staminate.
Plants with imperfect flowers are classified as:
monoecious-have separate male and female
flowers on the same plant (corn and pecan).
dioecious-species have separate male and female
plants (holly, ginko, papaya and pistachio)
Types of inflorescences:
Some plants bear only one flower called a solitary
flower.
Most inflorescences belong to one of two groupsracemes and cymes. Racemes bloom from the
bottom up while cymes bloom from the top down.
Pollination-is the transfer of pollen from an
anther to a stigma, either by wind or by
pollinators.
A chemical in the stigma stimulates pollen to
grow a long tube down the style to the ovules
inside the ovary.
When the pollen reaches the ovules, it releases
sperm, and fertilization typically occurs.
Cross-pollination-combines genetic material from
two parents.
Fruit
Fruit consists of fertilized, mature ovules (seeds)
plus the ovary wall, which may be fleshy as in an
apple, or dry and hard as in an acorn.
In some fruit the seeds are enclosed within the
ovary (apples, peaches, oranges, squash and
cucumbers.
In others, the seeds are situated on the outside of
the fruit tissue (corn and strawberries).
The only part of the fruit that has genes from both
parents is the seed. The rest is maternal.
Types of fruit
Simple-develops from a single ovary (cherries,
and peaches (drupe), pears and apples (pome),
and tomatoes (berry).
Tomatoes, squash, cucumbers, and eggplants all
develop from a flower and are considered to be
fruits.
Other types of simple fruit are dry. There wall
is either papery or leathery and hard (peanuts/
legume, poppies/capsule, maples/samara, and
walnuts/nut).
Types of fruit
Aggregate fruit-develops from a single flower with
many ovaries (strawberries, raspberries, and
blackberries).
The flower is a simple flower with one corolla, one
calyx, and one stem, but it has many pistils or
ovaries.
Each ovary is fertilized separately. If some ovules
are not pollinated successfully, the fruit will be
misshapen.
Types of fruit
Multiple fruits are derived from a tight cluster of
separate, independent flowers borne on a single
structure.
Each flower has its own calyx and corolla.
Examples are pines, pineapples and figs.
Seeds
Embryo-is a miniature plant in an arrested state of
development.
Endosperm-is a built in food supply.
Seed coat-hard outer covering which protects the
seed from disease and water loss.
Germination
Germination is a process whereby a seed goes from
a dormant state to an actively growing state.
Before this happen the seed must have water,
oxygen and a favorable temperature.
Some seeds such as celery also require light, while
others require darkness.
Radicle-is the first part of the seedling to emerge
from the seed. It develops the primary root and
grows downward.
Hypocotyl-is the structure between the radicle and
the first leaf-like structure and grows upward.
Cotyledons-encase the embryo.
Seed dormancy-because seeds are reproductive
structures, they have many mechanisms to ensure
their survival.
There are two types of seed dormancy:
seed coat dormancy-a hard seed does not allow
water to penetrate. A process called scarification
is used to break this dormancy.
embryo dormancy-these seeds must go through
a chilling before they will germinate.
Other factors affecting germination:
age of the seed
seedbed preparation
planting depth
moisture
Plant Growth
and Development
Photosynthesis
Respiration
Transpiration
The above 3 items
drive plant growth
Photosynthesis=‘s
carbon dioxide+water+sunlight=‘s Sugar+Oxygen
photosynthates-after producing carbohydrates,
the plant uses them for energy, stores them, or
builds them into complex compounds (oils/proteins).
The plant uses them when light is limited or stores
them in roots or fruit.
Photosynthesis occurs in the mesophyll in
chloroplasts which contain chlorophyll.
Chlorophyll is the pigment that makes leaves green.
It is responsible for trapping light from the sun.
Respiration
Carbohydrates (sugars and starches) made during
photosynthesis are converted to energy which the
plant uses for cell growth and building new tissue.
This chemical process in which sugars and starches
are converted to energy is called oxidation and is
similar to burning wood or coal to produce heat.
Controlled oxidation in a plant is called respiration.
Respiration does not depend on light so it goes on
during day and night.
Photosynthesis
• produces food
• stores energy
• uses water
• uses carbon dioxide
• releases oxygen
• occurs in sunlight
Respiration
• uses food
• releases energy
• produces water
• produces carbon dioxide
• uses oxygen
• occurs in the dark as
well as the light
Transpiration
When a leaf’s guard cell shrinks, it stomata open
and water is lost. As water is lost through the
stomata, more water has to be taken in through
the roots.
Transpiration is a necessary process for plants and
accounts for about 90% of the water that a plant
uses. Transpiration is affected by temperature,
humidity, and wind or air movement.
Transpiration is necessary for several things:
•Transporting minerals throughout the plant.
•Cooling the plant through evaporation
•Moving sugars and plant chemicals.
•Maintaining turgor pressure.
Environmental Factors Affecting Plant Growth
These factors affecting plant growth include include
light, temperature, water, humidity, and nutrition.
It is important to know how these factors affect
plant growth and development.
With a basic understanding of these factors, you
may be able manipulate plants to meet your needs.
By recognizing the role of these factors, you may be
better able to diagnose problems caused by
environmental stress.
Light - Quality, Quantity and Duration
Quantity - refers to intensity or concentration and
varies with the season.
Quality-light quality refers to the wavelength.
Sunlight supplies the complete range of wavelengths.
Plants absorb blue and red light. Blue light is mainly
responsible for vegetative growth. Red light when
combined with blue light encourages flowering.
Knowing which light source to use is important to
know for manipulating plant growth.
Duration or photoperiod refers to the amount of
time the plant is exposed to light.
It was first believed that day length was the main
factor affecting plant flowering. However, it was
later found out that it was the length of darkness.
Plants are classified into 3 day length categories:
•Short day length plants flower when they are
exposed to less than 12 hr. sunlight (mums, X-mas
cactus, poinsettias)
• Long day plants flower when the day length
exceeds 12 hours. This includes most summer
flowering plants and vegetables.
• Day neutral plants flower regardless of day
length such as tomatoes, corn, cucumber, and
some strawberry cultivars.
• Some plants don’t fit any category, but may
respond to combinations of day lengths such as
petunias.
Temperature
Generally may speed up most processes to a point.
When combined with day length, it may affect the
change from vegetative to reproductive.
Germination:
Generally cool-season crops (spinach, radish,
lettuce) germinate best at 55-65 degrees F. Warm
season crops germinate best at 65-75 degrees F.
Flowering:
Sometimes day length in combination with
temperature can be used to manipulate flowering.
Christmas cactus can be forced to bloom by
exposing it to more than 12 hours of darkness each
day and a temperature of 50-55 degrees F.
Crop quality:
Low temperatures reduce energy use and increase
sugar storage. Citrus is sweeter after cold
weather.
Adverse temp. may cause stunted growth and poor
quality. High temperatures cause bitter lettuce.
Thermoperiod - refers to daily temperature change.
Plants grow best when daytime temperature is 10 to
15 degrees higher than nighttime.
Under these conditions plant build-up and break
down tissues at an optimum temperature with
respiration at a nighttime minimum.
Temperatures higher than needed increases
respiration sometimes greater than photosynthesis
so photosynthates are used faster than they are
made.
Breaking dormancy - cold period
Hardiness - ability to withstand cold. Less daylight
and cooler temperatures stimulate plants to
reduce photosynthesis and ship nutrients to twigs,
buds, stems and roots.
Water and humidity - needed for photosynthesis,
respiration, turgor pressure, solvent for nutrients,
cooling factor, regulator for stomatal opening,
pressure to help roots move through soil and a
medium for biochemical reactions.
Plants In Communities
Ecology-interaction between plants is important for
gardeners. The study of this interaction is called
plant or landscape ecology.
Plant succession-as plants mature you may find that
some plants will have to be replaced.
Allelopathy-when some plants produce compounds in
their leaves, roots, or both that affect the growth
of other plants.
Plant hormones and growth regulatorsAre chemicals (natural and synthetic) that affect
flowering, aging; root growth; distortion and killing
of leaves, stems and other parts; prevention and
promotion of stem elongation; color enhancement of
fruit; prevention of leafing and leaf fall, and many
other conditions.
There are five groups of plant-growth-regulating
compounds:
1. Auxins cause several responses to plants.
a. bending toward a light source
(phototropism).
b. downward root growth (geotropism).
c. promotion of apical dominance
d. flower formation
e. fruit set and growth
f. formation of adventitious roots
Auxin is the active ingredient in most rooting
compounds.
2. Giberellins-stimulate cell division and elongation,
break seed dormancy and speed germination.
3. Cytokinins-occur in both plants and animals.
They promote cell division and are often used in
sterile for growing plants from tissue culture.
They are also used to delay aging (senescence).
4. Ethylene-it it only found in the gaseous form.
It induces ripening, causes leaves to droop
(epinasty) and drop (abscission), and promotes
senescence.
5. Abscisic acid (ABA) is a general plant-growth
inhibitor. It induces dormancy and prevents seeds
from germinating; causes abscission of leaves,
fruits and flowers; and causes stomata to close.
High concentration of ABA in guard cells during
drought stress probably play a role in closure.
THE END