Plants, Environment, Agriculture

How do we feed our future generations?

1. 1. Global population has tripled (1950-2020) yet we have harvested from the same amount of land

2. Crop production and yield has increased by

   • cultivating land covered in rainforests

   • enhancing food production from arable land

   • lowering food waste habits by humans

   • prioritizing staple crops > luxury crops

How can we increase yields and reduce environmental impact?

CURRENTLY:
1. monoculture = soil degradation, nutrient depletion, low biodiversity

2. bred/GMO crops = resistant weeds/crops

3. increase fertilizer = increased N2 into waters/algal bloom/eutrophication

4. pesticides = pest resistance, harms to human health

5. increased water usage

(Current Invasive Species) How can we control invasive species?

1. Stiga hermonthica = parasitic. attaches to plant roots and depletes nutrients

2. colorado beetle = attacks potato crops

3. wheat stem rust = hard to control. Some strains very resistant

Differences between traditional breeding and genetic modification

Traditional: crossing plants to produce offspring with desired traits
VS
Mutagenesis: changes in genome due to chemical exposure/radiation. Unpredictable and hard to assess
RNA interference: silencing targeted RNA
Transgenics: genetic material from one organism introduced into another. Recombinant DNA

How can plants contribute to energy crisis?

1. currently, 30% of maize is used for ethanol, when it could be used for food

2. miscanthus giganteus (C4!!) is a bioenergy crop grown on land unsuitable for food production, thus also preventing erosion

What new scientific approaches will be vital in the future?

1. antioxidant enriched tomatoes (reduces cancer/disease risk)

2. vitamin A enriched rice (immune health/vision)

3. converting non legumes to legumes (fixes N2)

Green Revolution

Modern agriculture techniques increase overall crop yield

C3 vs C4 cs CAM

C3 plants undergo photorespiration which is a wasteful process because O2 accumulates, and carbon is less efficiently converted to G3P in the Calvin Cycle. Thus, there is less photosynthetic activity. A majority of plants are C3, such as rice.
C4 plants shields O2 build up with closed stomata. Their "turbocharger" processes CO2 to G3P without O2 interference. C4 plants are much more efficient in hot/dry conditions, as CO2 is concentrated and photorespiration is minimized.
CAM plants take in CO2 when their stomata open only at night, when temps are lower and humidity is higher. This reduces the amount of water lost during transpiration, making CAM plants thrive the best in arid climates such as deserts.

Alexander von Humboldt

"Father of Ecology"

findings:

• Around the globe, plant morphology is different as you are in different parts of the world

• isotherms: lines on a map connecting points that have the same temperature

• isobars: lines on a map connecting points that have the same atmospheric pressure

Augustin de Candolle

findings:

• life forms and adapts because of temperature, moisture, and modular growth

• megatherm: organism that thrives in high heat biomes (ie rainforest)

• mesotherm: organism that thrives in middle heat biomes (ie grasslands)

• microtherm: organism that thrives in low heat biomes (ie forest)

• hekistotherm: organism that thrives in lowest heat biomes (ie tundra)

• xerophile: organism that thrives in the driest biomes (ie desert)

Vladimir Koppen

findings:

• classified biomes

Atmospheric Circulation

• In Hadley and Polar cells, lower air is pulled toward equator, and higher air moves toward poles. In Ferrel cells, lower air moves toward poles, and higher air is pulled toward equator. These cell movements induce the wetness and dryness of alternating biomes.

• closer to equator results in a faster speed of axis rotation, thus creating wind deflection

4 contrasting global biomes

1. desert

2. grasslands/savanna

3. tropical rainforest

4. tundra

Biomes

• alternate wet + dry

• altitude and latitude shift biome conditions

• affected by abiotic factors - precipitation, temperature, soil, geology

Contrasting global biome - 1. Hot Desert

• very dry, hot days/cold nights, thin/porous soils

• plant adaptations:

  1. C4 and CAM plants

  2. no leaves (cacti) means less surface area, thus less transpiration (water loss)

  3. morphology that can trap morning fog to hold onto moisturee

  4. light reflecting surfaces on plants instead of heat absorbing surfaces

Contrasting global biome - 2. Tundra

• cold - classified by permafrost, "permanently" frozen soil layer

• short growing season with moderate temperatures

• low-lying lands without trees

• plant adaptations:

  1. low meristems insulated by snow to keep themselves warm

  2. shifting to low optimal temperature

  3. dormancy by slowing growth to bear conditions

Contrasting global biome - 3. Tropical Rainforest

• canopies with different microclimates, thus different microecosystems

• highest biodiversity

• poor soil because nutrients/biomass all sitting above ground/in the canopies. Because of this, deforestation is especially destructive

• plant adaptations

  1. drip tips: large waxy leaves to rid fungus/mold otherwise growing from humidity

  2. prop roots: allowing transport in otherwise shallow soils

  3. epiphytes: plants growing on trees without interfering with the weak soil. They have no root system and absorb nutrients from the air

  4. adapting to low lighting due to canopies

Contrasting global biome - 4. Savanna

• grassland with scattered grasses and trees. Lots of herbivores

• plant adaptations:

  1. prickles/spines/thorns to deter herbivory

  2. indigestible/unpalatable structures (ex silica in grass)

  3. convergent evolution combatting similar issues

Anthropogenic biomes (Anthromes)

• terrestrial land following contemporary, human-altered transformations

• ex croplands, urban areas

Prehistoric/carboniferous forests

Had higher levels of CO2, lower levels of O2. Period of proliferation of all forms of life

Prokaryotic vs Eukaryotic Cells

Prokaryotic (Bacteria & archaea):

• nucleoid to store DNA

• plasmid for antibiotic resistance

• cell wall

• flagella for movement

Eukaryotic (eukarya):

• nucleus to store DNA

• peroxisomes to rid radicals/cancer cells

• mitochondrion to generate ATP

• (in plants) chloroplast & cell wall

Vascular system

• "plumbing" system in plants to transport water and minerals

• xylem: distributes water/minerals upwards, cool plants. Roots --> stem/leaves

• phloem: carries energy from photosynthesis down to roots. Leaves --> stem/roots

Evolution of photosynthesis

Photosynthesis evolved in bacteria. Eukaryotes began to photosynthesize via endosymbiosis of photosynthetic bacteria

Endosymbiosis

primary: cell takes in photosynthetic cyanobacteria. that cell now contains a chloroplast, and the chloroplast has a double membrane
secondary: a new cell takes in a primary endosymbiote. this secondary cell now contains a chloroplast

Evolution of land plants

1. First plants: Glaucophytes - unicellular, first photosynthetic organisms

2. Red Algae - multicellular, photosynthetic pigment, seaweed

3. Green Algae - freshwater algae that comprise phytoplankton. Green algae evolved so that zygotes wouldn't dry out on land

4. Charophytes - pond organisms with no vascular system

5. Land plants - land organisms with vascular system

Bryophytes

Nonvascular, simple land plants. Roots utilized for anchorage rather than water intake.
Liverworts, hornworts, moss.

Liverworts

Type of bryophyte with no stomata and slow photosynthesis by CO2 diffusion from atmosphere to cells.

Hornworts

Bryophyte with no leaves that fixes N2

Moss

diverse, first plants transporting sugar/water

Seed producing vascular plants: Angiosperms vs gymnosperms

Angiosperm = flowering, flat leaves, reproductive system in flowers, seasonal energy storage
ex apple tree, walnut tree, wheat
Gymnosperm = non flowering, needle leaves, reproductive system in cones, evergreen, lower CO2 turnover
ex pine, spruce

Evolution from Algae --> Angiosperm

1. Algae: photosynthetic ocean organism

2. (land) bryophytes: non-vascular land plants

3. (vascular) pteridophytes: seedless vascular plants

4. (seeds) gymnosperms: non-flowering vascular plants

5. (flowering) angiosperm: flowering vascular plants

Valivov Centers

Home origins of plants
Fertile Crescent: region with earliest domesticated crops

Top 5 grown crops

*Top 4 - 45% all grown crops

1. sugar

2. maize

3. rice

4. wheat

5. potato

Dietary components from plants

1. starches (potatoes, grasses)

2. sugar (cane)

3. vitamins (from leaves/stems)

4. protein (beans, legumes)

5. fats (nuts, oils)

Optimal qualities during domestication

1. tough stem (survives harvest)

2. large plant parts (optimizing growing resources)

3. color (antioxidants which lower disease/cancer risk)

Species

Individuals who:

• are capable of breeding

• producing fertile offspring

• have free exchange of genetic material

Speciation

two populations become genetically different/isolated from one another where they become unable to breed

Natural Selection

highest fitness will provide disproportionally more to future generations' gene pool because they are more likely to survive. "Survival of the Fittest"

classification

Kingdom, Phylum, Class, Order, Family, Genus, Species

Crop modification

examples:

1. modifying maize to have greater # of edible grains

2. increasing photosynthetic efficiency by altering angle of plant canopies to increase sun intake, CO2 absorbed and energy produced

3. modifying to have preferred color/taste/aesthetic of crops

Crop modification

examples:

1. modifying maize to have greater # of edible grains

2. increasing photosynthetic efficiency by altering angle of plant canopies to increase sun intake, CO2 absorbed and energy produced

3. modifying to have preferred color/taste/aesthetic of crops

Genetic diversity promotes

1. crop yield

2. quality

3. stress tolerance

Blight

parasitic fungus quickly infecting potatoes/tomatoes. No blight resistance can easily lead to famine

Plant likely to survive if

1. a lot of seeds w/ high germination likelihood

2. wide dispersion of seeds

3. qualities that deter interference by pathogens/predators

Successful crop/food cultivation

1. characteristics produced that are desired by the breeder

2. yields high volume of food

3. reliable crop spread and reproduction

4. disease/pest resistance

Ethnobotany

relationship between chemical properties/components of plants and indigenous use

Compound groups within ethnobotany

1. Glycosides - cardiac medicine. Strengthens heart/heartbeat

2. Alkaloids - Used for pain relief. N2 is a main component

3. Terpenes - essential oils and chemotherapy. Emitted by trees thus producing own microclimate

Bioremediation vs Phytoremediation

Bioremediation: microbes breaks downs and degrades organic pollutants

Phytoremediation: plants absorb/accumulate pollutants to remove them

Nutrients deemed essential if

1. an element-specific deficiency makes organism unable to survive/reproduce

2. element is directly involved in plant nutrition

Primary macronutrients

1. Nitrogen - comprises proteins/nucleic acids

2. Phosphorus - comprises nucleic acids, ATP, phospholipids

3. Potassium - involved in stomata opening, cell water balance, enzyme activation

SO2 effect in plants

Since humans have begun to clean SO2 out of atmosphere, plants who began to rely on it are now becoming sulfur deficient

Plant Response Curve (PRC)

Plants have an optimal range when responding to factors like temperature and nutrients. A surpassing the plant's limit of tolerance results in plant death. Different plants will have varying optimal ranges/responses

Effects of competition on PRC

species have to adapt to resource quantities that may be taken by other species. This results in a change in growth rate between species

Physiological Optimum vs Ecological Optimum

Physiological Optimum is the alleged optimum (when tested in a lab), whereas the ecological optimum is the optimum observed in nature, considering naturally occurring factors that affect it (ex competition)

High Nitrogen effects

• increase in species that thrive in N2 environment, wiping out anything else

• lower plant & animal biodiversity

• increased eutrophic waters/algal bloom

Limiting Factors Principle

if X element limits growth at a certain quantity, no other element's presence/quantity can create greater yield of that plant. With X element reaching a quantity past the plant's tolerance, it becomes indifferent to any other element

Cation exchange in clay particles

• CO2 from roots is released and mixes with H2O to form carbonic acid

• clay particles uptake H+ from carbonic acid and exchanges for a K ion that is given back to the root

Nitrogen Cycle

1. lightning fuses N2 + O2 into nitrates, which is rained into soil

2. N-fixing bacteria transform nitrates into ammonium (NH4)

3. Nitrifying bacteria oxidize NH4 to NO3

4. a) NO3 assimilates back into soil/roots

   b) Denitrification bacteria reduces NO3 back to N2 into atmosphere

   **anthropogenic mineral fertilizers adding excess N2 to this cycle

Amino Acid structure

amino group, side chain, carboxyl group

Mutualism of nitrogen fixation

N-fixing bacteria invade/colonize root cells to supply nitrate/ammonium to plants. In return, plants supply organic acids to the bacteria

Nitrogenase

enzyme used by N-fixing bacteria to fix N2. It reduces (adds H) N2 three times to create two molecules of NH3

Metallophytes

Plants capable of growing in soils with high amounts of heavy metals to avoid competition

Nutrients' movement due to

1. mass water flow leads to new root uptake

2. root moves to new area

3. diffusion. High concentration to low concentration

Phosphorus Cycle

1. rock erosion, mine extraction, and fertilizer all deposit phosphorus into bodies of water

2. dissolved phosphates are uptaken by plants in soils and organisms in surrounding waters

3. phosphates from organism decomposition goes to sediments, which becomes new rock through geologic uplift

Mycorrhiza fungi

produce hyphae/arbuscules, of a high surface area, which help with phosphorus transport in plants. (Greater surface area means a greater ability to gather material). The fungi concentrate metal ions in plant root tissue

Potassium (K)

maintains water balance/osmosis in a cell and performs special functions to open/close stomata. Therefore, less potassium means a greater chance of plant dehydration/drought.

Cell rehydration with potassium

Potassium is pumped into a dehydrated cell, so the cell is no longer flaccid and water can follow gradient to hydrate cell

Chlorosis

lack of chlorophyll in a plant (due to N2 deficiency). Leaves will begin to turn yellow

Types & effects of nitrogen deposition

1. wet deposition - ammonium (NH4) and nitrate (NO3) deposited via rain

2. dry deposition - physical contact with air/land

   *increased N2 deposition lead to increased harm (ex more insect damage on plants or less needle retention on trees)

Essential macronutrients in plants

N P K S Ca Mg

Serpentine soils

formed by weathered mineral containing high levels of toxic metals

Importance of Sulfur in plants

• in thiamine - Vitamin B10

• glutathione - chlorophyl synthesis

• biotin - strengthens hair (in humans)

Impacts of low Sulfur

• reduces formation of nodules in legumes. Thus less N fixation

• in wheat - leads to less gluten/poorer bread quality

Amino acid sulfoxides

• from sulfenic acid

• once-separated enzymes combine with sulfenic acid, producing eye-irritant sulfur oxide

• sulfuric acid burns the eyes. Eyes produce tears as response to wash acid away

Magnesium in plants

• component of chlorophyl - critical to photosynthesis

• phosphorus carrier

• part of protein synthesis

• Mg deficiency symptoms first appear in older/lower leaves

Calcium in plants

• Calcium Pectate - important in cell wall cementing for stability/structure

• sturdy bones (in mammals)

• component of amylase - catalyzes conversion of starch into sugar

Zinc in plants

• phytotoxin but needed in small amounts

• component of Carbonic Anhydrase - transforms CO2 to H2O and HCO3 (bicarbonate)

• (in mammals) supports immune function

• majority of plants’ enzyme activity levels decrease as Zn levels increase

Iron in plants

• oxygen in plants

• (mammals) need Fe to transport O2 in blood (hemoglobin)

• needed for N fixation

• component of Ferrodoxin: electron transfer in photosynthesis

Manganese

• catalyst in phenolic compound synthesis

• regulate proteins in plants

• needed in photophorylation

Sodium

• not essential for plants

• analogous to K (open/closing of stomata for water balance)

Chloride in plants

balances positive charges of K Ca Mg

Iodine

no major function in plants, but plants serve as carrier for animals

• Iodine helps with thyroid hormone production

Silicon in plants

• improves cell wall rigidity/structure

• forms barrier against parasitic fungi

• fights herbivory by making plants unpalatable/undigestible

Cobalt in plants

• synthesized by bacteria

• component of vitamin B12

• deficiency in humans - nervous system issues

Molybdenum

• component of nitrogenase

• helps with N fixation by root nodules —> important for legumes’ ability to fix N

• human deficiency —> developmental delay

Selenium in plants

• required for aiding disease resistance/antibody production

• low Se in soil/forage = land animals to develop White Muscle Disease (nutritional muscular dystrophy)

• plants are carriers for mammals —> Se is component of selenocysteine (human antioxidant)

Boron in plants

• affects plant reproduction

• deficiency - empty pollen grains, poor pollen vitality, stunted root growth/function

Nickel in plants

• vital component of urease

• catalyzes hydrolysis of urea into NH3 + CO2 (later absorbed into roots)

• Ni deficiency - build up of urea, necrosis (plant cell death) in leaf tips

• less Ni = less germination of seeds

Arsenic in plants

• metabolism of methionine (Amino Acid in DNA function)

• may be part of gene silencing

Aluminum in plants

• limits plant growth

• complicates phosphate —> phosphate deficiency

• harms root systems

meristems

dividing cell regions/points for plant growth

Optimal time to graze

plant quality and yield are at the same capacity, which produces maximum biomass for herbivores

Elongated tillers

• taller stems from reproductive development

• more likely to be grazed

Unelongated tillers

• shorter, compact tillers

Importance of grazing

• prevents grasses from growing high, drying up, oxidizing

• promotes biodiversity within soils

Ruminants

• ruminants have a specialized digestive system (rumen) to digest grasses/cellulose

• ex cows eat cud and regurgitate it into rumen

• ruminants revitalize grasslands

Oligophagous

certain animals’ food choice which is a few, related foods

monophagous

certain animals’ food choice which is one specific food only

Physical defense

• plant size can limit predators’ access to eat them

• abrasive plant tissues (though some predators adapt)

• silica making plant unpalatable

• hooks to trap insects

• hair/glands are physical/chemical deterrents

1. ex spines on nettle containing formic acid that injects anything that eats it

Chemical defense

• plant matter comprised of high cellulose, low nitrogen

• Glucosinolates - volatile oils released

• cyanide - released by plants, esp if leaf is crushed by herbivore