The Science of Plants in...

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

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

period

Evidence of crop cultivation

> 5,000

pea, barley, wheat, maize, millet,

lentil, beans, , rice, potato.

1,000 to

Sugar beet, sunflower, soybean,

alfalfa, onion, cotton.

< 1,000

rapeseed, coffee, rubber,

macademia nut.

barley, wheat,

lentil, pea

sugarbeet,

rapeseed

soybean.

millet,

coffee

cotton,

rubber

potato,

maize, bean

sunflower

alfalfa,

Macademia

1750 1800 1850 1900 1950 2000

Less developed

Developed

World Population

Food production has become more

dependable.

Improved transportation of food.

Raising family incomes to purchase

Improved housing and public hygene

and reduced infectious diseases.

Medical advances.

Saharan

Africa

Western

UrbanizationU

What, Where

and How

Industrial

Shifting

Trad. Intensive

Nomad/herd

Cereals Roots Pulses Oil Crops Vegatables Fruit

1955 = 1161.3 Ha

2005 = 1378.5 Ha

2005 +

+40%+36%

2005 +

People fed by a

single farmer

New better adapted and higher

yielding cultivars.

Better management of crops

and pastures.

Farm mechanism.

Inorganic fertilizers.

Pesticides.

eat –

let –

lm –

ut –

la –

ers –

Cereals Oilseeds Pulses

Roots Vegetable Fruits

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

SoybeanIL

WheatKS

BarleyND

Crop #1 #2 #3 #4 #5

Fresh Veg. CA

Proc. Veg. CA

Potato ID

Number 1 in the USA in:

Potato, Austrian winter pea, Wrinkled

pea , Small white/red bean , and Pink

bean production.

Lentils, Edible pea, and Garbanzo

Bean production.

Barley, Sugarbeet, Mint, Hops,

Onion production.

Carbohydrates - Wheat, potato, corn, rice, etc.◦ Simple carbohydrates and complex

carbohydrates

Lipids or fats◦ Three different types:

Triacylglyserol, Phospholipids, Cholesterol.

Protein.

Vitamins, Minerals, Water.

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

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

• 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

Reaction

CO2H2O

Reaction

Calvin

C6H12O6 = Glucose

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

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

Frequn

3/8 TT 2/8 Tt 3/8 tt

Parents TT x tt

Frequn

3/6 TT 2/6 Tt 1/6 tt

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

Soil borne

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

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

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

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).

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 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

Ti Plasmid

Gene of interest Selectable marker

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

Plant Scientists to

the Rescue

Oxygen

Carbon Dioxide

Carbon Dioxide Recycling With Biodiesel

Photosynthesis

Biodiesel

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

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