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The Science of Plants in Agriculture Pl.Sci 102
Lectures: M,W 10:30-11:20
Lab.: Tues – 6th Street Glasshouse
Introduce the role of plants in agriculture
with emphasis on world and USA
production. Overview the principles of
plant structure, growth and development
and management of our major agricultural
crops. Examine cropping systems,
sustainable agriculture and issues relating
to biotechnology, integrated pest
management, and environmental impacts.
Why are plants
important?
How did the worlds land become
inhabited with plants?
Why did agriculture begin?
Where and when did our agricultural
crops evolve?
What events have molded the genotype of
our crops since cultivation?
Tracheophytes
(vascular plants)
Bryophytes (non-
vascular plants)
Seeded
Seedless
Angiosperms
Gymnosperms
FernsClub mosses
Mosses
Hornworts
Liverworts
Fresh
water
alga
Time Period Event
2,500 m. 1st bacteria
500 m. 1st land plants (fungi & liverwort)
400 m. 1st gymnosperms
200 m. 1st angiosperms, 1st mammals, dinosaurs
rule the world
25 m. Monkeys and apes
3 m. Lucy
1 m. Homo sapiens
Time Scales
Why did humans become farmers and
not remain hunter/foragers?
“Natural selection favors plant types which would have greatest chance of survival, reproduction, and distribution of progeny”
“Human selection is the result of conscious decisions by the farmer or plant breeder to keep progeny from a certain parent over others”
When Did Crops Evolve
Time
period
Evidence of crop cultivation
> 5,000
years
pea, barley, wheat, maize, millet,
lentil, beans, , rice, potato.
1,000 to
5,000
years
Sugar beet, sunflower, soybean,
alfalfa, onion, cotton.
< 1,000
years
rapeseed, coffee, rubber,
macademia nut.
barley, wheat,
lentil, pea
.
sugarbeet,
rapeseed
..
rice,
soybean.
millet,
coffee
.
cotton,
rubber
.
.
potato,
maize, bean
.
sunflower
.
alfalfa,
apple
.
.
Macademia
0
1
2
3
4
5
6
1750 1800 1850 1900 1950 2000
Bil
lio
ns
Year
Less developed
Developed
World Population
Food production has become more
dependable.
Improved transportation of food.
Raising family incomes to purchase
food.
Improved housing and public hygene
and reduced infectious diseases.
Medical advances.
0
20
40
60
80
100
120
South
Asia
Saharan
Africa
East
Asia
Western
Asia
Latin
Am.
North
Am.
UrbanizationU
rban
Rura
l
What, Where
and How
Industrial
Shifting
Trad. Intensive
Nomad/herd
0
100
200
300
400
500
600
700
800
Cereals Roots Pulses Oil Crops Vegatables Fruit
1955
2005
1955 = 1161.3 Ha
2005 = 1378.5 Ha
0
2
4
6
8
10
12
14
Cereals Roots Pulses Oil Crops Vegatables Fruit
1955
2005 +
42%
+80%
+1
30%
+40%+36%
+1
23%
0
50
100
150
200
250
300
350
Cereals Roots Pulses Oil Crops Vegatables Fruit
1955
2005 +
17%
+62%
+1
6%
-18%
-30%
+2
8%
People fed by a
single farmer
New better adapted and higher
yielding cultivars.
Better management of crops
and pastures.
Farm mechanism.
Inorganic fertilizers.
Pesticides.
0
100
200
300
400
500
600
700M
aiz
e –
59
6 m
Mt
Ric
e –
59
3 m
Mt
Wh
eat –
58
2 m
Mt
Ba
rley
–1
36
mM
t
So
rgh
um
–6
0 m
Mt
Mil
let –
27
mM
t
So
yb
ean
–1
62
mM
t
Oil
pa
lm –
98
mM
t
Co
con
ut –
40
mM
t
Ca
no
la –
40
mM
t
Dry
bea
n –
20
mM
t
Oth
ers –
20
mM
t
Cereals Oilseeds Pulses
0
50
100
150
200
250
300
350
Roots Vegetable Fruits
Po
tato
–3
02
mM
t
Ca
ssa
va
–1
70
mM
t
Sw
eet
po
tato
-1
38
mM
t
Gra
pes
–6
0 m
Mt
Ban
an
a –
58
mM
t
To
ma
to -
10
0 m
Mt
Ca
bb
ag
e -
50
mM
t
On
ion
-5
0 m
Mt
Ora
ng
es -
66
mM
t
Ap
ple
-6
0 m
Mt
Crop Area M acre
Yield Value Mill US$
Corn 80.9 160.4 Bu/a $ 23,032
Soybean 73.9 42.5 Bu/a $ 16,098
Wheat 59.7 43.5 Bu/a $ 7,192
Barley 4.5 69.4Bu/a $ 839
Fresh Veg. 1.9 - $ 9,815
Process Veg. 1.3 - $ 1,392
Potato 1.2 391 cwt $ 2,564
Crop #1 #2 #3 #4 #5
CornIA
19%
IL
18%
NE
11%
MN
9%
IN
8%
SoybeanIL
16%
IA
16%
MN
8%
MO
7%
NE
7%
WheatKS
15%
ND
14%
MT
8%
OK
8%
WA
7%
BarleyND
33%
MT
17%
ID
21%
WA
17%
CO
3%
Crop #1 #2 #3 #4 #5
Fresh Veg. CA
49%
FL
9%
AZ
8%
GA
4%
TX
4%
Proc. Veg. CA
68%
WA
6%
WI
6%
MI
6%
OR
2%
Potato ID
32%
WA
23%
WI
7%
OH
6%
CO
6%
0
200
400
600
800
1000
1200
1400
Number 1 in the USA in:
Potato, Austrian winter pea, Wrinkled
pea , Small white/red bean , and Pink
bean production.
Number 2 in the USA in:
Lentils, Edible pea, and Garbanzo
Bean production.
Number 3 in the USA in:
Barley, Sugarbeet, Mint, Hops,
Onion production.
Food
Carbohydrates - Wheat, potato, corn, rice, etc.◦ Simple carbohydrates and complex
carbohydrates
Lipids or fats◦ Three different types:
Triacylglyserol, Phospholipids, Cholesterol.
Protein.
Vitamins, Minerals, Water.
2005
Growth and Development
of Plants
• Manipulate plant growth, and optimize and
predict production.
• Genetically modify plants to increase
productivity or quality.
• Determine the effects of pests and diseases
on plant growth to develop natural resistance.
• Determine how plants grow to discover ways
to kill them (herbicides).
• Cell wall: provides protection and structure.
• Plasma membrane: controls movement of minerals, metabolites and water into and out of the cell.
• Chloroplast: site of photosynthesis, starch biosynthesis and starch accumulation.
• Golgi apparatus: site of synthesis of polysaccharides such as hemicellulose needed for cell walls.
• Mitochondria: site of all biochemical reactions of respiration.
• Endoplasmic reticulum: site of protein synthesis.
• Vacuole: site for storage of proteins.
• Nucleus : site of the majority of the genetic information (DNA) and is the site of transcription
Apical
Meristem
Ground tissues
Dermal tissues
Vascular tissues
Ground tissues
◦ Parenchyma
◦ Collenchyma
◦ Sclerenchyma
Dermal tissues
◦ Epidermis
◦ Stometes
◦ Hairs/tricomes
Vascular tissues
◦ Phloem
◦ Xylem
Ground tissue
Vascular tissue
Dermal tissue
There are three
primary regions of
shoot and root development
• Region of cell division -
apical meristem.
• Region of cell elongation.
• Region of cell maturation.
Reproduction, Seeds and
Propagation
Self-
pollinator
Out-pollinator
Flowers
Seed Treatments
Germination
enhancement
Fungicides
Insecticides
• Auxins
• Cytokinins
• Gibberellins
• Ethylene
• Abscisic acid
• Brassinosteroids
• Jamonic acid
• Auxins: stimulates cell elongation, mediates
tropism.
• Cytokinins: stimulates cell division, in ratio with
auxins regulate meristematic cell division.
• Gibberellins: breaks seed dormancy.
• Abscisic acid: stimulates the closure of stomata.
• Ethylene: is associated with fruit ripening.
• Brassinosteroids: regulate plant stature.
• Jasmonic acid: give a response to wounding of
plants and associated with pest resistance.
Phototropism
2,4-Dichlorophenoxyacetic acid (2,4-D)
The ratio of auxin to cytokinin in a
tissue dictates growth of axillary
meristems
• High auxin / Low cytokinins =
meristem remains dormant.
• Low auxin / High cytokinins =
meristem starts to under go cell
division and starts to grow.
GA3 Control
Ethylene
Regulate cell expansion and are one of the most important hormones that regulate stature.
Without them, plants are tiny dwarves, with reduced vasculature and roots, and are infertile.
They also regulate senescence or aging.
Brassinosteroids
• Major functions is in regulating plant growth include growth inhibition, senescence, and leaf abscission.
• It has an important role in response to wounding of plants plant resistance.
• When plants are attacked by insects, they respond by releasing JasmonisAcid, which inhibits the insects' ability to digest protein.
• It is also responsible for tuber formation in potatoes, yams, and onions.
Jasmonic Acid
Solar Energy
Ionosphere
Stratosphere
Troposphere
• Ozone in the upper atmosphere serves
as a protective shield by absorbing most
of the harmful ultraviolet radiation.
• Atmospheric gases do not absorb much
of the sun‟s radiation between 400 and
700 nm.
• This is notable because this band of
radiation is called photosynthetic active
radiation.
• This is the most important for life on
Earth.
Light Intensity
Light Spectrum
Light Quality
• Light affects plant processes in the range
of 380 to 800 nm.
• Photosynthesis requires a narrower band
than this.
• Blue light (440 um) and red light (680
um) are more effective than green light
(520 um)
• As a result green light is reflected more –
hence green plants.
• Seed germination in light sensitive seeds.
• De-etiolation, greening of young
seedlings
• Stem growth in plants that are competing
for light with their neighboring plants.
• Related to plant receptors called
phytochrome.
• R:FR ratio detected by a plant is
dependant on how close and how big are
neighboring plants (competition).
• R:FR ration is high (no competition) =
compact plants with dark leaves.
• R:FR ratio is low (neighbor competition)
= taller plants, with light green color,
necrosis leaves, weak!
Day-length response in plants.
Can affect:◦Flowering
◦Bud dormancy in woody plants
◦Formation of vegetables (i.e. storage
organs like rutabaga, potato, etc.)
Plants can be either:◦ Long day plants (LDP), or short night plants.
◦ Short day plants (SDP), or long night plants.
◦ Day neutral plants (DNP), which are neutral to day (or night) lengths.
Day lengths plants have a critical day length (CDL) which must be satisfied in order that the plant will flower.
• Atmospheric gasses are composed of
78% nitrogen (N2) = 780,000 ppm.
• 21% oxygen (O2) = 210,000 ppm.
• 0.035% carbon dioxide (CO2) = 350
ppm.
Gases
• All plants have a minimum temperature
below which there is no plant growth –
often below 4oC (39oF).
• Plants also have a maximum
temperature limit whereby plants cease
to function – usually no higher than
50oC (122oF).
Photosynthesis in plants converts light energy in the form of photons into chemical energy in the
form of ATP and NADPH
The energy stored in ATP and NADPH can then be used to convert CO2 and H2O (water) into simple
sugars
An added bonus of photosynthesis is the
production of O2 (oxygen) by the plant
Photosynthesis
Light
Reaction
Dark
Reaction
NADPH
& H+
NADP+
CO2H2O
Light
Reaction
O2
Light
Calvin
Cycle
ATP
ADP
Pi
C6H12O6 = Glucose
light
6CO2 + 12H2O C6H12O6 + 6 H2O + 6O2
energy
Photosynthesis
Why is soil important for the
majority of agricultural crops?
Soil is critical as a holding for
plants, and supplies water and
nutrients that are critical for
photosynthesis and plant
function.
Soil Profile
Soil Types
Soil Particle Size
Dried
Waterlogged Field capacity
Water Movement
Water PotentialAir -95
Leaf -0.8
Stem -0.7
Root -0.6
Soil -0.4
• Calcium
• Potassium
• Magnesium
• Nitrogen
• Sulfur
• Phosphorous
• Boron
• Iron
• Copper
• Nickel
• Chlorine
• Zinc
• Manganese
Macro Nutrients Micro Nutrients
N-Deficiency
P-Deficiency
K-Deficiency
A gene is a DNA sequence coding for a
single polypeptide, t-RNA or r-RNA
Promoter region Gene Sequence Terminator region
DNA RNA protein
nucleic nucleic amino
acids acids acids
So changing the nucleic acid sequence of DNA can result in changing the amino acid
sequence of a protein
• Genotype v Phenotype
• Homozygous v Heterozygous
• Dominant v Additive
Genetic modification of crop plants.
Increase productivity.Have better end-use
quality.Can be produced with
fewer input costs, with greater profit.
Types of Cultivar
Pure line.
Out breeding populations.
Clones.
Hybrids.
Breeding Objectives
Genetic Variation
Selection
•People
•Politics
•Economics
What factors are
to consider in
setting Breeding
Objectives?
Identify or create
genetic variability
Select for desirable
recombinants
Plant Breeding Operations
Identify or create genetic variability
[4x = 44]
Seedless Watermelon
[2x = 22] x
[2x = 22][3x = 22] xMale Sterile
Identify or create
genetic variability
Select for desirable
recombinants
Plant Breeding Operations
Parents TT x tt
F1 Tt
F2
Frequn
TT
¼
Tt
½
tt
¼
F3
Frequn
TT
¼
TT1/8
Tt
¼
tt1/8
tt
¼
3/8 TT 2/8 Tt 3/8 tt
Parents TT x tt
F1 Tt
F2
Frequn
TT
¼
Tt
½
tt
¼
F3
Frequn
TT
¼
TT1/8
Tt
¼
tt1/8
3/6 TT 2/6 Tt 1/6 tt
X
Segregation
Which pests and diseases affect crops
Effect of plant pests and diseases
Types of plant resistance
Mechanism for pest and disease
resistance
Pest management systems.
Air borne
fungi
Soil borne
fungi
Bacteria
Viruses
Eelworms
Insects
Other, Incl
Mammals
Reduce useable yield.
•All diseases and pests.
Reduce end-use quality and
storability.
•Most crops, especially fruits and
vegetables.
Susceptible Host
Pathogen
Favorable
environment
No
disease
No
disease
No
disease
No
disease
No
disease
No
disease
Disease
Vertical resistanceControlled by a single gene.
Results in distinct resistance classes.
Resistance is usually absolute (yes or no).
Horizontal resistance.Controlled by multiple genes.
Results in continuously variable levels of resistance.
Usually resistance is not absolute.
AvirulentUnable to overcome the resistance and
hence unable to infect or injure the host plant.
Virulent Able to overcome the resistance and hence
able to infect or injure the host plant.
For each resistance gene in the host plant
there is a gene in the pathogen that
determines whether the pathogen is:
Relationship between
resistance genes and
virulent genes is called
Locks & Keys
Locks (dominant resistance genes)
can only be opened with the right
keys (recessive virulent genes).
Easy to manipulate genetically.
Identification of resistant phenotypes is easier.
Race specific.
Resistance tends not to be durable for some disease types.
Advantages
Disadvantages
Horizontal resistance more durable than vertical resistance.
Ability to control a wide spectrum of races.
New pathotypes have difficulty overcoming all resistance loci.
Advantages
Probability of combining all (or many) resistance alleles into a single genotype are low.
Disadvantages
Resistance due to lack of infection.• Hypersensitivity
• Mechanical
Downey Mildew
(Peronospora parasotica)
Susceptible Resistant
Resistance due to lack of spread
after infection.• Antibiosis: Plant resistance that reduces,
survival, growth, development, or
reproduction of pests feeding on the plant.
• Antixenosis: Plant resistance that reduces
pest preference or acceptance of the plant.
Russian wheat aphid
Resistant plants exhibit less leaf
rolling, lower aphid population
increase and lower reduction in
plant biomass.
Resistant varieties combine
both, antibiosis and
tolerance.
Escape: Plant morphology avoids disease.
Tolerance: Plant “resistance” that results in a plant suffering less injury or yield loss than a susceptible plant when both are equally infested.
Harvest date
Final infection
Final infection
Using genes from Bacillus
thuringiensis (B.t.).
What is a weed?
Yield loss as they compete for:
• Interceptable light.
• Water.
• Nutrients.
Harbor Pests:
• Over winter insects, host to diseases
and cause infection.
Reduce Crop quality
• Weed seed contamination.
Mechanical:
• Non-selective herbicidal cultivation.
• Inter-row cultivation.
• Hand weeding.
Cultural:
• Inter-cropping.
Biological
• Insects.
Chemical
Group Description
1
Foliar, monocots, ACCase (Acetyl CoA Carboxytase) inhibitors,
binds to ACCase and disrupts fatty acid synthesis, which leads to
membrane degeneration (i.e. Hoelon, Assure II).
2Foliar and soil, dicots, ALS (Acetolactate synthase) inhibitors, binds
to ALS and disrupts synthesis of branched amino acids (i.e. Beyond).
3Soil applied, mainly dicots, Tubulin inhibitors, interferes with cell
division (Treflan).
4Foliar, mainly dicots , synthetic auxins, upsets plant growth regulator
balance by mimicking an increase of auxins (i.e. 2,4-D).
5,6&7Foliar and soil, mainly dicots, binds to a pigment in photosystem II
and disrupts photosynthesis (Triazine, Sencor).
9
Foliar, nonselective, EPES inhibitor, binds to EPES synthase and
disrupts pathway, which is responsible for producing the precursors of
aromatic amino acids (i.e. Roundup).
Biological control:• Encourage natural preditors and parasites.• Biopesticides.
Cultural control:• Resistant cultivars; trap crops; intercropping.• Cultivation & tillage; crop rotation, timing.
Mechanical & Physical control:• Screens; traps.
Reproductive & Genetic control:• Introduce harmful pest genes; mass release of sterile
insects.
Chemical control:• Pesticides used in an appropriate manner; hormones.
Produced by bacteria as a
defense mechanism against
phages. Enzymes act like
scissors by cutting phage
DNA at specific sites.
P1
P2
P1 P2 F2
Molecular Markers
R S R S S R R R S R
Marker assisted selection.
◦ Difficult to evaluate characters.
◦ Quantitative Trait Loci (QTL‟s)
DNA finger printing to identify genotypes (or cultivars).
◦ To secure proprietary ownership.
◦ Select parents with known genetic distance.
Cytological information (mainly in interspecific hybrids).
Saturated gene mapping.
Possible to transfer single genes from other species and non-plants into plant.
Have transgenes expressed and to function successfully.
Bypass natural barriers which limit sexual gene transfer.
Allow breeders to utilize gene from completely unrelated species.
Create new variability beyond that currently available in germplasm.
Tumor Producing Nopaline
Synthesis
T-DNA
Ti Plasmid
Gene of interest Selectable marker
T-DNA
Ti Plasmid
Promotor
Check functionality of tranformed plants
Select cells that have been transformed
Regenerate whole plants from single transformed cells
Develop a suitable construct
Develop a mechanism to transfer the gene into the target plant
Find a desirable gene
Myths and concerns regarding
GM crops.
• Pharmaceuticals from plants.
• Health issues.
• Environmental issues.
• Legal and ethical issues.
Population explosion.
Soil quality.
Air quality.
Water quality.
Pesticides in the environment.
Genetic diversity.
Acid Rain
Water Erosion
Wind Erosion
Toxins
Monsanto (US)
Dupont (US)
Syngenta (Swiss)
Group1 Limagrain France)
Land O'Lakes (US)
KWS Ag (Germany)
Bayer Crop Sci (Germany)
Sakata (Japan)
DLF-Trifolium (Denmark)
Takii (Japan)
$4,964,000,000
$396,000,000
$347,000,000
$391,000,000
$,524,000,000
$702,000,000
$917,000,000
$1,226,000,000
$2,018,000,000
$3,300,000,000
Top 10 = 68%, Top 4 = 53%. Top 3 = 47%, Monsanto = 23% world seed
2007
Data
Plant Scientists to
the Rescue
Oil
Oxygen
Carbon Dioxide
Water
Carbon Dioxide Recycling With Biodiesel
H2O
H2O
H2O
Photosynthesis
Biodiesel
Plant
Feed Stock
Switch grass
Wood chips
Hybrid Poplars
Household trash
Wheat Straw
Renewable, reduce imports
Lower air emissions
Biodegradable
Biodiesel smells yummy!
Lubricants
Surfactants
Engine Oils
Paints and printing inks
Dep. of Ag. Warning:
Plows and disks can harm
agriculture and the
environment
Reduced grower inputs
Reduced fuel emissions
Avoids soil erosion
Improved soil structure
Avoids soil compaction
Improved water holding
More earth worms
Drip Irrigation
Fertilizer placement
Biological pesticides.
Pesticides derived from natural materials.◦ Either animals, plants, bacteria, or minerals.
Examples: garlic, mint, Brassica plants, baking soda.
There are over 175 registered biopesticide active ingredients and over 700 biopesticidal products.
Microbial (microorganism) pesticides.◦ Bacterium, fungus, virus, protozoan, or alge)
◦ Most widely know is Bacillus thurengiensis.
Plant pesticides.◦ Breakdown products from plant tissues.
◦ Walnut trees and allelopathy.
◦ Bt resistant plants.
Biochemical pesticides.◦ Non-synthetic pesticidal compounds.
◦ Plant growth regulators and pheromones.
Usually less toxic than synthetic compounds.
Generally affect only one specific pest, in contrast to broad-spectrum pesticides.
Often are effective in very low quantities.Often decompose quickly, and hence
avoiding pollution problems.Most effective as one part of a IPM
system.
Efficacy - they don‟t work.◦ Multiple „snake oil‟ products are
available.
Expensive.◦ Rather synthetic pesticides are
cheep.
Usually multiple biopesticidesare needed to be effective.◦ Usually require IPM systems
Plant Breeder
Biochemist
Cytogeneticist
Biotechnologist
Ecologist
Geneticist
Horticulturalist
Marketing Specialist
Physiologist
Production specialist
Plant protection
Food scientist
Agricultural sales
Irrigation specialist
Recreational hort.
Farmer
Have a Very Merry
Christmas and Good
Luck to you all in 2011