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Leaves
- collect carbon to make the plant grow
- site of photosynthesis: “exchange” gases by pulling CO2 out of air combined with light and water to make sugars and give off oxygen
- do it to build themselves
Stem
supports plant; has tissues to transport sugars, water, and nutrients from leaves down to roots or vice versa
Flavor Savr Tomato
first commercially grown GMO; prompted public outcry
Plant Domestication
similar set of traits were selected in all crops throughout history
Gigantism of harvested organs
larger fruits or seeds
High Harvest Index
ratio of grain to total shoot dry matter
Seed dormancy
seeds unable to germinate
seed non-shattering
shedding of seeds when they ripen
Adaptation to photoperiod
measure daylength to flower at specific time of year
Resistance to Diseases & Pests
immunity and other defense mechanisms
Eliminate toxic compounds
many plants make poisons to deter predators
Pharming
re-breeding beneficial compounds into crops that was previously bred out in favor of larger or sweeter fruits
Natural Variation
spontaneous mutations in DNA that change the physiology of the plant. Altered plants w good traits can be selected and propagated
Induced Variation
treating plants w chemicals, radiation, transposable elements that cause DNA mutation to occur faster than normal, then select plants with desirable traits
Steps:
Grow plants that have variation.
Look for good traits
mating plants
combining 2 or more plants with desirable traits and finding offspring with all desired traits
Steps:
Identify desired traits (can come from natural or induced variants)
Mate variants with individual desired traits
Examine offspring and choose the plant with both desired traits
Problem of Natural or Induced Variation
Random chance of finding good traits
Problems of Mating Plants
Long generation time- ~2/year-wheat
Lots of genes- 20,000-30,000!
Random assortment of gene
Green Revolution Improvements
- higher yield, but only in proportion to added fertilizer (nitrogen)
- semi-dwarf to support added weight for mechanical harvest, avoid “lodging” (drooping)
- lower tillering (branching) to develop energy to fruits
- maturity synchronized and early flowering independent of day0length fast generation times
- disease resistance
Biological Effects of Green Revolution
Non-sustainable use of resources
Shift to high intensity farming: resource-intensive (water, fertilizers, pesticides), MONEY
Natural resources exhausted: soil and water pollution
Social and Economic Effects of Green Revolution
globalization of agri markets (end of susbsistence farming)
food security (population increases, depletion of petroleum and water resources)
reduced farm labor: rural to urban migrations
economic: need credit to purchase inputs & seeds, rich-poor gap widens, crop failure creates catastrophic debt
Genetic Engineering
adding DNA sequences that produce desired traits—commonly referred to as GMOs
Steps:
Targeted transformation of genetic material into plant (via agrobacterium or biolistic). This
adds new DNA into a plant genome
Problems with Genetic Engineering
- not culturally accepted
- all crops are genetically modified; genetic crosses mixes genes from each parent; genetic engineering introduces 1 or few defined genes into crop w other traits already optimized; no mixing
- both introduce “traits” but differ in how much and what accompanies them
- potential for escape of harmful species
- patented control over food supply
Corn Borer Problem
- corn borers were eating corn crops
- bacillus thuringiensis naturally produce toxin crystals that kill corn borers when eaten
- spore produces a crystal that dissolve and activate toxins in gut of caterpillar
- Bt corn: Bt plant products contain the bacteria gene that produces the toxin that kills the caterpillars
- non-carcinogenic or toxic to humans bc we don’t have the receptor; humans ingesting 1000mg/days for 5 days show no ill effect; UV light degraded: does not pollute environment; prevents insecticide spraying on fields (prevents pollinator deaths)
Bt Crops
Contain the bacteria gene that produces the toxin that kills the caterpillars
Non-carcinogenic or toxic to humans- we don’t have the receptor
Humans ingesting 1000mg/day for 5 days show no ill effect
UV light (sunlight)-degraded- does not pollute environment extensively
Prevents insecticide spraying on fields- prevents pollinator deaths
“Roundup Ready” Problem
weeds compete for limited water, light and nutrients
observation: glyphosate kills plants by preventing amino acid (protein) production; gplyphosate binds to EPSPS or 5-enolpyruvyl-shikimate synthase
modified EPSPS does not bind to glyphosate
problems: natural variation occurs, so weeds are starting to survive
potential problem 2018: evidence that roundup may cause cancer
Barrier Cells
cuticle, epidermis, stomata
Cuticle & Epidermis
protective layer against insects and evaporation of water
Stomata
“mouth” in Greek; they open and close to allow exchange of gases
Energy Cells
Spongy & Palisade mesophyll; contain chloroplasts which contain chlorophyll and do the photosynthesis
Spongy Mesophyll
has holes for efficient gas exchange
Palisade Mesophyll
highly densely packed cells at the top bc they collect light from the sun
Transport Cells
veins
Veins
pump water from the ground and sugars throughout the plant
Distinct Features of Plant Cells
have fiber cell wall made of cellulose
have chloroplast
Combustion
experiment to prove that there are gases in the air
fuel source uses oxygen, goes through combustion to yield heat, H2O, and CO2
photosynthesis is opposite of combustion: it takes water and CO2 and creating fuel and O2
plants are only living organisms that can do this
Jan Baptist von Helmont
tried to figure out how plants generated biomass
Weighed soil
Planted willow sapling
Weighed willow sapling and soil after 5 years
Result: Sapling gained 164 pounds, soil had the same mass
hypothesized that there were micronutrients in the water that contributed to biomass, didn’t know about photosynthesis
Joseph Priestly
in sealed chamber burning candle and mouse dies
when he added plant, the mouse and candle was still alive
hypothesized that plants use/exchange gas: lead to discovery of O2 and that atmosphere is made up of many gases
Dephlogisticated air
Air that can support life
Phlogisticated air
Air that cannot support life
Jan Ingen-Housz
did same chamber, plant, mouse experiment with a difference: there was no light, and the mouse died
hypothesized that plants need light to convert gases
Photosynthesis
converts gas into sugar
6CO2 + 6H20 —(light)> C6H12O6 + 6O2
Chlorophyll
traps light as energy; collects light and points it toward CO2 and water like a rubber band
Chloroplasts
contain chlorophyll
Simple Sugars (glucose, fructose, sucrose)
use for their own growth or to store in fruit so seeds have burst of energy when they germinate
Storage Sugar (starch)
put it in chloroplasts and seeds to keep long term source in case they run out of simple sugars
Cell Wall
composed of glucose-based molecules cellulose/pectin/lignin
Cellulose
most abundant biopolymer on Earth (there’s more carbon in it than any other biopolymer)
Lignin
second most abundant biopolymer on Earth
Protein
sugars put towards biomolecules of protein to assist RNA, DNA, and RuBisCO
RuBisCO
protein that helps with photosynthesis; also most abundant protein on Earth
Drop-In
fuel we can put into gas tanks
Wood
burns cell wall material
pros:
125,000 years ago the control of burning wood ss fire lead to increased protection from predators and microbes, increased warmth, and nocturnal activity
Readily available
Still used
Renewable
cons:
Health risks associated with inhaling smoke
Greenhouse gas emissions
Conversion to other useful sources of energy is difficult
1st Generation Biofuel
fermentation of foodstocks to make ethanol or use of plant oils for biodiesel
Ferment sugars from corn, rice, wheat, and sugarcane to make ethanol
Extract oil from oil-storing seeds: peanut, soy, sunflower, jatropha
—>Blend fuel-grade seed oils for diesel or ethanol into gasoline
pros:
Conventional methods used to produce fuel
Clean burning=less health hazard/less greenhouse gas emission
Renewable- we can grow more corn
cons:
Competition with foodstocks- fuel prices drive food prices and vice versa
2nd Generation Biofuel
fermentation of non-food biomass
glucose is converted to complicated polymers to protect them from outside organisms
cut up the biomass into small pieces
heat it
treat w chemicals to split cellulose molecules apart to make accessible to enzymes
they’ve developed enzymes to go in and break up cellulose like termite
purify those enzymes and treat those cellulose so that they are broken down into sugars
then it goes through 1st gen process
pros:
Clean burning=less health hazard/less greenhouse gas emission
Less competition with foodstocks
Biomass is highly abundant
Renewable
cons:
Unconventional methods used to produce fuel
Need industrial processing plants and enzymes for digestion
Fermentation
gives off CO2 as byproduct
distillation (extracting ethanol from mixture): you treat it with nutrients, store it and bring to market
solid byproducts can be used for animal feed
process is energy intensive
3rd Generation Biofuel
biodiesel produced directly in microorganisms
Microorganisms (algae) are modified to produce high yields of oil (lipids)
Algae are grown in “bioreactors” at high density using non-potable water
Converting sunlight energy as oil rather than sugar
pros:
No competition with food supply
Can be used in vehicles that are diesel powered
cons:
New biotech needed to produce oil in high quantities
New industrial methods
Fossil Fuels
pros:
It is estimated that phytomass (plants) is 1000X zoomass (animals) - are a PLANT derived fuel
Fossil fuels include coal, oil, and natural gas
High energy in small package
cons:
Millions to hundreds of millions of years to form
Health hazardous emissions
700k-2.2mil deaths per year in China due to air pollution
Greenhouse gases leading to climate change
Giant Miscanthus
grass species that can grow well in poor soil and little water
trying to grow them so they won’t compete with biomass
C12O2
lighter and more abundant isotope of carbon; preferred by plants
C13O2
heavier and less abundant isotope; less preferred by plants
Anthropogenic Reason
Burning fossil fuels increases amt of C12O2 in the atmosphere and decreases concentration of C13O2
Human burning fossil fuels has caused a lower ratio of C13O2 to C12O2
Water
warmer temps will change location of these sources
plants are moving toward north and south, where more access to this exists
Light
moving crops away from equator changes productivity
1. current croplands will be affected by change in plant composition as those places will be increasing dry, moving plants away from equator
2. we will also have to move crops away from equator
a. but moving plants northward changes the yield as the change in location can change the plant cycle
Temperature
plants have optimal growing/reproductive temps
1. growing seasons are being affected by high temps during growing season
2. in Japan, ppl have been tracking emergence of cherry blossoms for past ~800 years
Reforestation Drones
when equipped with seedling canisters, can plant 300 seedling canisters in 1 hectare in 18 mins
Harnessing Plants Initiative
normal crop plants have shallow roots bc we water them all the time
Dr Joanne Chory is trying to bioengineer crops
Suberin
a complex but stable (lasts for hundreds of years) chain of carbons naturally occurring in plants
Ideal Plants
can capture carbon and store it in the ground through enlarged systems of suberin-rich roots store carbon deep in the soil and resist decomposition to release significantly less CO2
Acid Rain
in 1963, scientists discovered that pollution from factories was causing rain to become more acidic
in 1980s acid rain entered public consciousness, but we now hear very little about this
acid rain is caused by presence of nitrogen dioxide and sulfur dioxide in the atmosphere
acid rain was causing forest and ecosystem damage due to heavily populated areas and factories
problem was recognized and solved using a combo of science and policy changes
Science: scientists discovered acid rain and linked it to pollution emitted from factories
Awareness: in the 1980s the media picked up on story and alerted public to issue
Policy: in 1990s, govt under George Bush became involved and implemented policy (Clean Air Act) which set goals for reduction of pollution emission based on scientific evidence
Action: those goals were met and the problem was avoided
Kudzu Vine
was brought in as erosion control mechanism
spread over and grew over tops of other plants
now populates US and kills off native species
Wheat Rust Disease
along coast of Africa, disease started affecting the wheat
Found wild resistant wheat cultivar
Crossed “high producing” with “resistant” and got high producing and resistant wheat
We need to maintain “gene pools”
Salicylic Acid
compound from willow tree; pain relievers (aspirin, ibuprofen, etc) are all derivatives of compound
Internal Signals
communicate from cell to cell or tissue to tissue
Aspirin (or acetyl salicylic acid)
Plants make this as a way to communicate that they are under attack
plant hormone that triggers defense response
Plant Biotic Interactions
defend themselves: poison intruders
make themselves attractive: scents to attract pollinators, predators, or seed dispersers
Pathogenic
many (~99%) plant chemicals are for defense
Tannins
cause astringency (dryness) to detract herbivores
Anthocyanins
red color of strawberries attracts herbivores to spread seeds
Fennel
sends signals to attract the braconid wasp; braconid wasp lays eggs in cocoons of moths and butterflies and kills it
Symbiotic
Plants and microbes or animals are using each other for survival
Roots
collect nitrogen, nutrients, and water from soil
Nitrogen
Important for many plant processes because needed for amino acids and nucleic acids
Rhizobia
plant bacteria that form symbioses with plants and convert nitrogen gas from the air into usable nitrogen
Nitrogen Cycle
Denitrifying bacteria convert nitrogen in atmosphere into nitrate which plants pick up
nitrifying bacteria convert ammonia to nitrite and nitrite to nitrate
denitrifying bacteria will use nitrate and give back nitrogen into the atmosphere
plants that form symbiotic relationship with denitryfing bacteria: plants take nitrogen and give bacteria water and sugar
animals then eat plants and get its nitrogen
decomposers take nitrogen from bodies of dead organisms and return it to soil
Synthetic
humans are exploiting plant-microbe interactions to make GMOs and to biopharm
Biopharming
using plants as biological factories to produce biomolecules for human health
pros: inexpensive, stable in storage, not using transgenic animals
cons: Potential contamination of food supply or environment
Agrobacterium
causes crown gall; used to create transgenic plants (GMOs)
bacteria can associate w plant cell and inject its DNA into plant cell and incorporate into plant chromosome
P. Infestans
killed potatoes everywhere and caused Irish Potato Famine; most destructive pathogen of potato ($6.7 bn/ur)
causes potato late blight
Irish potato famine
oomycete model organisms, hemibiotrophic
adopts rapidly to overcome control measures and bred resistance
Potatoes
underground tubers highly effective at nutrient storage
ranks second to soybean in protein produced per acre and ranks first in energy and protein production; single potato provides 50% of the recommended daily allowance of vitamin C, compared with 0% for rice and wheat, 21% of potassium, 12% of fiber, and balanced protein
True Tubers
plants that are modified plant stems found underground; potatoes most common example of true tubers
Lumper
Ireland’s exclusive potato variety prior to the famine; grow well in wet conditions of Ireland
were produced asexually using their “eyes” which can make a new plant—one potato can yield 6 potato plants
Monoculture
plants propagated through asexual reproduction
Asexual Reproduction
offspring are genetically identical to parent
pros: fast, good for stable/safe environments, no partners needed nearby
cons: monoculture, lack of genetic diversity, leaves plants at risk for disease
Sexual Reproduction
offspring are genetically distinct from either parent
Budding
form of asexual reproduction in which a new individual develops from an outgrowth or bud due to cell division at one particular site
Vegetative Propagation
underground stems that shoot up another plant (ex. bamboo rhizomes)
Fragmentation
a form of asexual reproduction where an organism breaks into smaller parts or fragments, each capable of growing independently into a new organism (ex. cutting off a branch, treating it with a bit of hormone and it will grow roots)
Oomycete life cycle
zoospores are produced and released from sporangia
zoospores infect leaves
zoospores infect tubers
lesions develop on leaves
sporangia, formed on diseased seedlings and leaves, are dispersed to healthy leaves
seedlings produced by infected tubers become diseased
devastating bc sporangia are quickly spread by wind
Masting
synchronized flowering and seed production of a population of plants resulting in a massive sexual reproductive event-usually after long periods of time
Mautam, “Bamboo Death”
masting for bamboo occurs every ~48 years
environmental conditions do not control masting
all bamboo from melocanna baccifera flower in the same year regardless of where they are on earth; we don’t know how this works
provides a fitness advantage: monocultures are bad when pests evolve/are introduced
why do they mast together in the same year?
scientists hypothesize that rodents eat any seeds that drop early, so if they drop them all together, there will be too much fruit for rodents to eat, pushing sexual reproduction of bamboo together 48 years apart