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1. Basic Botany, Plant Physiology,
and Environmental Effects on
Plant Growth
The University of Tennessee
Master Gardener Program
Updated January 2002
2. Objectives
To develop a basic
understanding of:
Botany
Plant Physiology
Environmental Factors that
affect Plant Growth
To apply this basic
understanding to home
gardening.
3. Topics
Plant Parts and Functions
Stems
Leaves
Buds
Roots
Flowers
Fruit
Seed
Plant Development
Photosynthesis
Respiration
Transpiration
Environmental Factors
Affecting Plant Growth
Temperature
Light
Water
4. Plant Parts
Reproductive
Flower Buds
Flower
Fruit
Seeds
Plant parts of sexual
reproduction
Vegetative
Roots
Stems
Leaves
Leaf Buds
Often used in asexual
reproduction (vegetative)
6. Stems
Stems support:
Buds
Flowers
Leaves
Stems transport:
Water
Minerals
Sugars
Nodes
The points where leaves
develop along a stem
Regions of high cellular
activity
The distance between nodes
(internode) is affected by:
Light (etiolation)
Water
Nutrients (N and micros)
Genetics
7. Nodes and Buds
Many plants develop one
or more buds at the nodes
(axillary buds)
Axillary buds may grow
into lateral branches
When pruning a plant it is
very important to make cuts
just above axillary buds:
Axillary buds grow
Wound heals quickly
When making cuttings,
they should be made just
below a node:
Many plants root more
easily at nodes, some only
at nodes.
Managing light, water,
nutrients, and genetics are
important to healthy
transplant production!
11. Types of Stems
Shoot
A young stem with leaves
present
Twig
A stem less than 1 year old
with no leaves present
(dormant)
Branch
A stem more than 1 year
old, with lateral buds
Trunk
A main stem of a woody
plant
Trees generally have a single
trunk
Shrubs often have 2 or more
trunks
Vines
A long trailing stem that is
able to support itself by
winding around other plants
12. Types of Stems and Modifications
Canes
A stem that lives only a
year or two
Contain a large amount pith
(soft tissue) in the center
Stem modifications
Above-Ground
Crowns
Stolons
Spurs
Below-Ground
Bulbs
Corms
Rhizomes
Tubers
All of these have buds or
leaves present
Can you think of examples
of these structures?
16. Vascular Tissue:
“The Plants Circulatory System”
Xylem
Transports water, nutrients, &
minerals from roots to upper
portions of the plant
Forms the “wood” of woody
plants
Phloem
Conducts sugars from leaves to
growing points, fruits, & storage
areas
Comprises much of the bark of
woody plants
Cambium
Cambium is the
meristematic tissue (the site
of cell division and growth)
It is located between the
xylem and phloem and
produces both tissues
Other meristematic tissue is
found at the apical bud,
where stem elongation
takes place
17. Arrangements of Vascular Tissue
“Dicots”
Vascular tissue form rings
Woody plants
“Monocots”
Vascular tissue arranged in
bundles
Grasses, Orchids, Lilies
Lack cambium tissue
between xylem and phloem
Stems of dicots tend to
grow in diameter, while
stems of monocots tend
not to increase in diameter
What does knowing about
these tissues reveal to you
about:
Damage to the bark of a
tree?
Grafting?
19. Life Span of a Stem
We often classify stems by
how long they live:
Annual
Produce seed and die within
1 year
Biennials
Produce vegetative structures
and food storage organs the
first year
Reproduction takes place the
second year and the plant
dies
When stressed, biennials can
go through the entire process
in 1 year (bolting)
Perennials
Live 3 or more years
Usually produce flowers and
seeds every year
Herbaceous Perennial
Shoots which die back to the
ground every year
“Biennial Perennials”
20. Leaves
Leaves:
Are attached to the stem by
petioles
Consist of:
Blade
Midrib
Smaller Veins
Function
To manufacture sugars in a
process called photosynthesis
Functions
Petiole:
Expands the leaf area and
orients the leaf
Blade:
Provides a large area for the
efficient absorption of light
Midrib and Veins:
Conducts water, sugar, and
other compounds throughout
the leaf
22. Outer Leaf Structure
Epidermis
Outer protective layer
Trichomes
Extensions of epidermis that
make leaves feel like velvet
Cuticle
Waxy layer (cutin) in some plants
that protects plants from:
Dehydration
Penetration by some diseases
Guard Cells
Special epidermal cells that are
capable of enlarging and
contracting
Stomates
Openings that develop between
enlarged guard cells
Usually on the underneath side of
the leaf
Regulate the passage of water,
oxygen, and carbon dioxide in
and out of the leaf
23. Inner Leaf Structure
Mesophyll
Where photosynthesis occurs
Is comprised of 2 layers
Palisade cells
Parenchyma layer
Palisade Cells
Dense upper layers of the leaf
Parenchyma Layer
Lower spongy area with
considerable air space
Chloroplasts
Actual site of photosynthesis
Found in the palisade cells and
the parenchyma layer
Some plants vary leaf
thickness with environmental
conditions
Special Leaves
Bracts
Tendrils
Cotyledons
28. Leaf Shape and Plant Identification
Leaves are one of the primary
characteristics in plant
identification
Veining
“Structure”
Shape
Margins
Arrangement
Leaf Veins
Veins are the continuation of
vascular tissue from the stem,
through the petiole
Veining Patterns
Parallel
Run parallel with length of
the leaf
Are connected by minute,
straight veins
Prominent in monocots
Net
Pinnate
Palmate
Prominent in dicots
33. Common Leaf Shapes
Acuminate: Tapering to a long, narrow point.
Acute: Ending in an acute angle, with a
sharp but, not acuminate point.
Obtuse: Tapering to a rounded edge.
Sagittate: Arrowhead-shaped, with two
pointed lower lobes.
Truncate: Having a relatively square end.
35. Common Leaf Margins
Entire: A smooth edge with no teeth or notches.
Serrate: Having small, sharp teeth pointed toward the apex.
Dentate: Having teeth ending in an acute angle, pointing
outward.
Crenate: Having rounded teeth.
Sinuate: Having a pronounced sinus or wavy margin.
Incised: Margin cut into sharp, deep, irregular teeth or incisions.
Lobed: Incisions extend less than halfway to the midrib.
Cleft: Incisions extend more than halfway to the midrib.
36. Leaf Arrangement
Leaf arrangement along the
stem
Rosulate
Basal leaves form a rosette
Short internodes
Opposite
Two leaves exactly opposite
Alternate
Steps or spiraled
Whorled
Circles of three or more leaves
Uses of Leaves
Food
Humans
Animals
Wild
Livestock
Ornamental
Color
Shape
Soil Amendments
39. Buds
Buds are undeveloped
shoots from which leaf or
flower parts arise
Bud Scales
Small, leathery, modified
leaves that cover buds
Bud Scale Scars
Scars formed when the bud
scales are removed
Used in plant identification
Types of Buds
Terminal – dominant
Auxin
Lateral or axillary
Adventitious
May originate from
internodes, leaves, or callus
tissue of stems or roots
Chilling Requirements
Bud Use
40. Roots
Principal Functions
Obvious
Absorb Water
Nutrient Uptake
Also
Transport water and nutrients
to the stem
Anchor / Support
Serve as storage organs
Propagation
Parts or Zones of Growth
Merisematic Zone
Where new cells are formed
Root Cap – protects root tip
Zone of Elongation
Cells increase in size and
push root
Zone of Maturation
Cells differentiate
Root hairs form – short-lived,
small roots - absorption
42. Root Systems
Two types of Root
Systems
Tap
Develops a main tap root
with various amounts of
lateral rooting
Fibrous
Develops small roots that
spread out in a mat-like
growth
Uses
Food
Humans
Fresh
Processed
Animals ?
Medicinal
Dried
Fresh ?
43. Flowers
Flowers are generally the
showiest part of the plant, but
they also serve a purpose
Sexual Reproduction
Color and / or
Odor
attracts pollinators (insects)
Flowers are least influenced by
environmental conditions;
therefore they are important in
plant identification.
44. Flower Parts
Sepals
Small, green leaf-like
structures at the base of the
flower that protect the
flower bud
Collectively – Calyx
Petals
Colored and aromatic part
Collectively – Corolla
The number of sepals and
/ or petals helps identify
the family or genera
Dicots generally have
multiples of 4 or 5
Monocots generally have
multiples of 3
Example
Members of the “Rose”
family have 5 petals and
sepals.
45. Reproductive Flower Parts
Female
Pistil (shaped like a
bowling pin)
Stigma (top)
Style (middle)
Ovary (bottom)
Placenta
Ovules – develop into seed
after pollination
Male
Stamen (flowers often have
a cluster of stamens around
the pistil)
Anther (pollen sac)
Pollen is produced by the
anther
Filament (“stem”) supports
the anther
47. Types of Flowers
Complete – all four parts
Incomplete – lacks one
part
Perfect – contains both
function pistils and
stamens
Imperfect – lacks a
functioning pistil or
stamen
Self-pollination
Cross-pollination
Monoecious – both male
and female flowers on one
plant
Dioecious – contains only
male or female flowers on
a single plant
50. What Is a Fruit?
Something you eat for
desert (not with the entrée)
Botanically, fruit is a
ripened ovary
Mature ovules (seeds)
Ovary wall (flesh)
Examples
Tomatoes, cucumber,
eggplant, beans
Types of fruit
Simple
Single flower – tomato
Aggregate (compound)
Single flower with many
ovaries – strawberry
Multiple
Tight cluster of many flowers
– pineapple
51. Seed Structure
Three Main Parts
Embryo – partially developed
plant in a dormant state
Radicle – embryonic stem
Hypocotyl – stem
Cotyledons – seed leaves
Plumule – underdeveloped stem
and leaves
Endosperm – food source
Seed Coat – protection from
insects, diseases, and germination
Seed Growth
Germination – resumption
of seed growth
Moisture
Oxygen
Favorable temperature
Light (sometimes)
53. Seed Germination and Storage
Most seeds require time
after maturity before they
will germinate.
Others will require:
Stratification
Scarification
Soaking
Time, time, time!
Storage
Seeds are living things!
They “live” longer when
maintained in a cool and
dry environment.
Keep seed packets air tight
(except beans ?)
Store in a refrigerator or
freezer
54. Plant Growth and Development
Three major processes
Photosynthesis
Respiration
Transpiration
55. Photosynthesis
Photosynthesis – “to put
together with light”
Requirements:
Light
Carbon Dioxide
Water
Suitable Temperature
Process – very complicated,
but a simple description
Carbon dioxide and water are
combined using solar energy
Simple sugars (glucose is
formed and oxygen is give off
(in the chloroplasts)
Simple sugars are then
converted into more complex
sugars and starches; and stored
All green tissue is capable of
photosynthesis, but most takes
place in the leaves
What limits photosynthesis?
56. Respiration and Transpiration
Respiration is the
“opposite” of
photosynthesis
Carbohydrates are broken
down and the energy
released is used for life
processes
As night-time
temperatures increase,
respiration increases
Transpiration is the process
by which plants loose water
vapor
90% of the water entering a
plant is transpired
Water movement is important
in moving nutrients, minerals,
sugars, and other compounds;
as well as maintaining turgor
pressure and evaporative
cooling
58. Photosynthesis vs. Respiration
Photosynthesis
Produces sugars
Stores energy
Releases oxygen
Uses water
Uses carbon dioxide
Occurs in sunlight
Occurs in chloroplast
Respiration
Uses sugars for energy
Release energy
Uses oxygen
Produces water
Produces carbon dioxide
Occurs in dark and light
Occurs in all cells
60. Temperature
Temperature is the main
environmental factor affecting
plant growth
Germination
Cool-Season vs. Warm-Season
Hardiness
Cold – Desiccation
Heat
Growth and fruit set
Temperature influences quality!
62. Light
Three principal
characteristics:
Quantity
Intensity or brightness
Phototropism
Quality
Color or wavelengths
Red and blue light are most
important
Green is reflected by the
plant
Duration
Photoperiod – amount of time
a plant is exposed
Short-Day
Flower during long nights
Mums and poinsettia
Day-Neutral
Not influenced by day
length
Ever-bearing strawberries
Long-Day
Flower during short nights
Most summer plants
64. Water
Water comprises most of
all living things!
The plant is no different!
Main component of
protoplasm – the living part
of the cell
Water Acquisition
Root hairs
Vascular tissue
Stomates
Quality
Low in salts
Temperature
Quantity
Too much
Diseases
Too little
Wilting
Special structures
Leaves