MB&B Exam 3

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:

1. Grow plants that have variation.

2. Look for good traits

mating plants

combining 2 or more plants with desirable traits and finding offspring with all desired traits

Steps:

1. Identify desired traits (can come from natural or induced variants)

2. Mate variants with individual desired traits

3. 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:

1. 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

1. Weighed soil

2. Planted willow sapling

3. 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

1. Ferment sugars from corn, rice, wheat, and sugarcane to make ethanol

2. Extract oil from oil-storing seeds: peanut, soy, sunflower, jatropha

3. —>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

3. Burning fossil fuels increases amt of C12O2 in the atmosphere and decreases concentration of C13O2

4. Human burning fossil fuels has caused a lower ratio of C13O2 to C12O2

Water

1. warmer temps will change location of these sources

   1. 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

1. normal crop plants have shallow roots bc we water them all the time

2. 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

1. in 1963, scientists discovered that pollution from factories was causing rain to become more acidic

   1. in 1980s acid rain entered public consciousness, but we now hear very little about this

2. acid rain is caused by presence of nitrogen dioxide and sulfur dioxide in the atmosphere

3. acid rain was causing forest and ecosystem damage due to heavily populated areas and factories

4. problem was recognized and solved using a combo of science and policy changes

   1. Science: scientists discovered acid rain and linked it to pollution emitted from factories

   2. Awareness: in the 1980s the media picked up on story and alerted public to issue

   3. 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

   4. 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