Test 2 Flashcards
What are the main minerals a plant needs?
- Nitrogen
- Potassium
- Phosphate
- Sulfur
- Calcium
- Magnesium
Where do the minerals for a plant come from?
- decomposition of organic molecules
- the atmosphere
- weathering and erosion of rocks
What is the proximate source of nutrients?
- decomposition of organic molecules
- the most immediate source
What is the ultimate source of nutrients?
- Weathering and erosion of rocks
- the origin
What weathers and erodes rocks?
- Wind
- Water
- Acids
a) H20 + CO2 –> H2CO3/carbonic acid
b) plants
Nitrogen
- proteins, nucleic acids, phospholipids
- from decomposition and atmosphere
What affects decomposition rate?
- temperature
a) cold climates = slow decomp rate / warm climates = faster decomp rate - acids/pH
b) low pH/high acidity = slower decomp rate
c) high pH/low acidity = faster decomp rate
Atmosphere and Nitrogen
- plants cannot use N2
- rely on nitrogen fixation
Nitrogen fixation
- converting N2 to an organic molecule
- only prokaryotes can undergo nitrogen fixation
Fixation
- converting something from an inorganic state to an organic state
Phosphate
- phospholipids, ATP, NADP, NADPH, ADP, Nucleic Acids
- from decomposition and weathering
Igneous Rocks
- rock formed from molten rock
- very little phosphate
- granite
Sedimentary Rock
- rock formed from sediment and decomposed organic molecules
- lots of phosphate
- limestone
Sulfur
- found in some amino acids
- CoenzymeA
Potassium
- stomatal function
- rich in guard cells and area around them
Calcium
- found in cell wall
Magnesium
- found in chlorophyll
Cofactor
An inorganic substance that binds to an enzyme and activates and active site (only required for certain enzymes)
What minerals are cofactors?
- potassium
- calcium
- magnesium
4 Steps of Water and Nutrient Uptake
- movement of h2o and nutrients into cortex
- Movement of nutrients from cortex to xylem
- movement of h2o into xylem
- vertical transportation
Movement of H2O and nutrients into cortex
a) passive transport
- water and dissolved molecules seep between teh cells into the cortex
b) active transport
- selective uptake of specific nutrients by the epidermal cells
- draws water into cells because the cell is hypertonic compared to the hypotonic soil
Tonicity
Hypertonic
Hypotonic
tonicity - total solute concentration of a solution
hypertonic - higher solute concentration than a reference solution
hypotonic - lower solute concentration that a reference solution
Movement of nutrients from cortex to xylem
a) active transport across endodermis
- active transport through endodermal into xylem
Movement of H2O into xylem
- occurs through osmosis
- high solute concentration in xylem draws in water
Vertical Transportation
2 mechanisms
1. root pressure
2. transpiration
Root pressure
- hydrostatic pressure caused by pumping water into the xylem
- causes the water and nutrients to move up the xylem because xylem is highly lignified
- occurs in smaller plants
Transpiration
- caused by the evaporation of water due to the stomata and pulls water and nutrients up through the xylem tissue
Stomata functions
- transpiration
- gas exchange
3 Photosynthesis Mechanisms based on H2O Availabilty
C3, C4, and CAM
- differs by when and where carbon fixation occurs
- differs by when and where LDR and LIR occur
C3 Photosynthesis
- LDR and LIR occurs in mesophyll cells
Carbon fixing step: CO2 + RuBP (5C) + Rubisco –> 2 PGA (3C) –> Glucose - not good for xerophytes
Rubisco
- enzyme that binds to RuBP and catalyzes the rxn
- has low affinity to CO2
- requires a high [CO2]
- bad enzyme because it catalyzes photorespiration
Photorespiration
- RuBP (5C) + O2 + Rubisco –> 1 PGA (3C) + 1 PGAL
- PGAL is toxic
- bad for the plants
- rate of photoresp. increases a [CO2] decreases and [O2] increases
C4 Photosynthesis
- LDR occurs in mesophyll cells
- LIR occurs in bundle sheath
1. carbon fixing step; occurs in mesophyll cells: CO2 + PEP + PEP Carboxylase –> Malate (4C)
Malate then goes to the bundle sheath
2. occurs at the bundle sheath: Malate (4C) —> CO2 + Pyruvate (3C)
3. LIR, occurs in bundle sheath: CO2 + RuBP (5C) + Rubisco –> 2 PGA (3C) –> 4 Glucose
4. Pyruvate (3C) + ATP + Pi –> ADP + PPi + PEP (goes back to mesophyll cells)
What does C4 Photosynthesis allow / its function?
- It separates rubisco from the source of O2 (mesophyll cells)
- Allows plant to close stomata for a period of time
- creates a high concentration of CO2 around rubisco
CAM Photosynthesis
- common in cacti
- LDR and LIR occur in the same cell (either mesophyll cells or photosynthetic cortex)
1. carbon fixing step; at NIGHT; stoma is open: CO2 + PEP + PEP Carboxylase –> Malate (4C)
2. during the day; stoma is closed: Malate (4C) —> CO2 + Pyruvate (3C)
3. during the day; stoma is closed: CO2 + RuBP (5C) + Rubisco –> 2 PGA (3C) –> 4 Glucose
4. during the day; stoma is closed: Pyruvate (3C) + ATP + Pi –> ADP + PPi + PEP
In CAM photosynthesis, why is CO2 stored as malate?
At night, it allows the plant to keep a low [CO2], which permits the diffusion of CO2 into the plant.
Why is C4 more efficient than C3?
- Rubisco has a low affinity to CO2, so it requires a high concentration of CO2 to bind to it
- C3 requires the stomata to be open more frequently to have a high concentration of CO2
- In C4, CO2 reacts with PEP and PEP carboxylase, which has a high affinity to CO2, so it doesn’t require a high concentration of CO2
- The CO2 is then converted to malate and sent to the bundle sheath, creating a high concentration of CO2 around Rubisco
- this reduces the chance for photorespiration
Explain why CAM is more efficient than C3
- Rubisco has a low affinity to CO2, so it requires a high concentration of CO2 to bind to it
- C3 requires the stomata to be open more frequently to have a high concentration of CO2
- In CAM, the stomata is open during the night to allow the diffusion of CO2 into the cells while minimizing water loss.
- The CO2 is then stored as malate, which keeps the CO2 concentration low in the mesophyll cells, which allows CO2 to continuously diffuse into the mesophyll cells while the stomata is open.
- During the day, the stomata closes to prevent water loss, and the Malate stored is converted back to CO2 for use.
Phloem Transport
- from source to sink
- high pressure to low pressure
Phloem Transport: Source
- leaves, roots
- active transport of sugars from source to the phloem
- high [solute] ; hypertonic to the xylem
- draws water in from xylem creating a high hydrostatic pressure
Phloem Transport: Sink
- meristem, roots, flowers
- facilitated diffusion of sugars from phloem to sink
- hypotonic to xylem
- water is drawn from the phloem to the xylem through osmosis creating a low hydrostatic pressure
Reproduction: Gymmnosperms and Angiosperms
- reproduce through pollen
Pollen
- male gametophyte encased in sporopollenin
- allows for reproduction with lack of water
Pollen Dispersal
- 2 approaches
1. Wind Pollenation
2. Animal Pollenation
Wind Pollenation
- all gymnosperms
- 25% of angiosperms
- green
- small petals to allow wind flow
- large stigma and anther
- long style and filaments
- stems at the end of branches
- LOTS of pollen
- grow close together
- flower in early spring so other plants don’t block wind
Animal Pollination
- mutualism (plant gets fertilization and animal gets food: nectar or pollen)
- 75% of angiosperms
Major pollinators
- insects
- birds
- bats
Benefits of Animal Pollination for Plants
- more efficient pollen transfer (pollinator fidelity)
- efficient over greater distance
Pollinator Fidelity
- occurs when a pollinator visits the same flower species while foraging
Coevolutionary Trends in plant/pollinator interactions
- flower characteristics
- specialization
Coevolution
- reciprocal evolution of 2 interacting species
Flower Characteristic Trend
- color and odors
- color ranges from uv to yellow (insects cannot see red light)
- bat and moth pollinated plants are big white odiferous flowers
- bird pollinated plants are red or orange
Specialization Trend
- an obligate species specific relationship
- benefits:
a) guaranteed food supply for pollinator
b) very efficient pollen transport - requires a stable ecosystem
- ex: tropical ecosystems
Negatives of Self-Pollination
- reduces genetic variation within the population; limits ability to adapt to changing environment
- inbreeding depression
Inbreeding depression
reduction of fitness caused by increased expression of negative alleles
Positives of Self-Pollination
- guaranteed reproduction
a. harsh environments
b. pioneer species - inexpensive
a. typically reproduces smaller plants
Pioneer species
- a species that has adapted to rapidly colonize and survive in newly created habitats
- ex: islands, glaciers melting and leaving land behind
Mechanisms to Reduce Self-Pollination
- dioecious
- physical separation of male and female parts
- temporal separation
- self incompatability
Temporal separation
- different flowering times of male and female flowers
- ex: avocados
Self Incompatability
- ability to recognize its own pollen and prevent germination
Asexual Reproduction Examples
- runners
- rhizomes
- suckers
- apomixis
Runners
above ground lateral stems that produce plants
Rhizomes
below ground lateral stems that produce above ground leaves
Suckers
- new plants growing from a root system of an existing plant
- ex: pando
Apomixis
- asexual reproduction using sexual machinery
- no fertilization, no meiosis
- Sporophyte (2N) –> megasporocyte (in ovule; 2N) —> megaspore (2N) –> megagametophyte with egg (2N) –> embryo/seed (2N)
- –> = mitosis
Shade Tolerant Plant
- able to germinate and grow in the shade of an existing plant
- few large seeds
- seed has a lot of endosperm that allows the seedling to develop a decent root system and a few large leaves before it runs out of energy
- requires protection from predators
Where does germination occur?
in or on the ground
Shade Tolerant Plant Protection Mechanisms
- thick heavy seed coat
- promotes caching behavior - chemical protection
- ex: tanins
- polyphenolic compounds
- very tart
- bind to and inhibit digestive enzymes - masting
Caching behavior
- animals storing food for later use
- when seeds get buried, most will germinate because they are not eaten
Shade Intolerant Plant
- needs full light to germinate and grow
1. many very small seeds ; wind dispersed
2. fewer, slightly larger seeds ; fruit dispersal
Masting
- intermittent massive production of the seef crop by all the nut producing trees
- satiates (satisfies) the predator population
Germination
- embryo is very dry (5-20% h2o)
1. seed coat becomes permeable to h2o
2. embryo soaks up h2o, swells, and breaks seed coat
3. rapid transfer of energy from the endosperm to the apical meristems in the embryo
Universal Requirements for Germination
- water (not too much)
- oxygen
Other potential requirements for germination
- light (red)
- temperature
- scarification
- chemicals
Red Light for germination
- shade intolerant and/or pioneer species (need full light)
- red light is absent in shade and doesn’t penetrate deep into soil; tells plant that it is in an open area and close to the surface
Temperature for germination
- temp must be above some threshold value
- cold stratification
Cold stratification
- seed requires a threshold number of days below a certain temp (5 degrees celsius) before it can germinate after the temp exceeds threshold
Scarification for Germination
- chemical or physical damage to the seed coat
- ex:
a. wind blown seeds
b. digestive enzymes
c. serotiny
Serotiny
- heat from a fire is required for germination
Chemicals for Germination
- ex: chaparral habitat
- grass seeds require a chemical from the smoke to germinate
Growth in Response to the Environment
- 2 phenomena
1. tropism
2. photomorphogenesis
Tropism
- directional growth in response to an environmental cue
- 2 types
1. phototropism
2. gravitropism
Phototropism
- apical meristem detects blue light and sends auxin down the darker side of the stem
- auxin causes cell elongation in stem tissue
- stem bends towards the light
Gravitropism
- auxin from above ground apical meristem is sent to the columella cells through phloem
- columella cells directs auxin to lower side of root and inhibits cell elongation
- top side grows faster than bottom side and causes root to bend
Photomorphogenesis
- change in growth form in response to a change in the light environment
- controlled by the phytochrome system
- etiolation and de-etiolation
Etiolation
- rapid growth of seedling, producing a long, thin, pale stem with no branches and few pale leaves
- results from lack of red light
De-etiolation
- slow growth of seedling, producing a short, stout, green stem with big green leaves
- results from the presence of red light
Phytochrome system
- protein pigment complex in apical meristems and leaves
- comes in two forms
1. Pr (red light)
2. Pfr (far red light)
Pr phytochrome system
- inactive state
- sensitive to red light
Pfr phytochrome system
- active state
- sensitive to far red light
- causes or prevents a process
What happens to the phytochrome system if red light is present?
- if red light is present, the plant is in the open, and the plant is in the active state (Pfr)
- Pfr prevents etiolation, resulting in de-etiolated growth
What happens to the phytochrome system if red light is absent?
- if red light is absent, the plant is in the shade, and the plant is in the inactive state (Pr)
- results in etiolated growth
3 Types of Flowering Plants
- Short Day Plants
- Long Day Plants
- Day-Neutral Plants
Short Day Plants
- flower when conditions are good and the day length is shorter than some critical value
- spring or fall
Long Day Plants
- flower when conditions are good and the day length is longer than some critical value
- summer or late fall
Day-Neutral Plants
- flower when conditions are good
- tropical environment
- pioneer species
What does flowering depend on?
conditions and length of night
Why are pioneer species day-neutral plants?
- pioneer species adapt to rapidly colonize and survive in newly created habitats, so it is more efficient for them to reproduce as frequently as possible
Phytosystem affects on flowering: spring
- short day (Pfr state) / long night (Pr state)
- SDP flowers
- LDP does not flower
Phytosystem affects on flowering: summer
- long day (Pfr state) / short night (Pr state)
- SDP does not flower
- LDP flowers
Pfr affect on SDP
Pfr inhibits SDP from flowering
Pfr affect on LDP
Pfr induces LDP to flower
Hormone
- a chemical produced by one tissue (endocrine) that causes a response in another tissue (target)
- can by synergetic or antagonistic to each other
Synergetic hormones
hormones that work together
Antagonistic hormones
hormones that have opposing affects
5 Major Hormones
- Auxin
- Gibberellic acid (giberrellins)
- Cytokinins
- Abscisic acid
- Ethylene
Auxin produced by stem apical meristems
- induces cell elongation in stem tissue
- inhibits cell elongation in root tissue
- blocks branching in stem tissue
- induces branching in root tissue
Auxin produced from leaves
- inhibits abscission
Auxin produces from an immature embryo
- induces fruit development
- inhibits fruit abscission
- creates seedless fruit
Abscission
- the natural detachment of parts of a plant
2 Versions of Seedless Fruit (Parthenocarpy)
- natural mutation
- Adaptive Parthenocarpy
Natural Mutation of Seedless Fruit
- ovule or egg secretes auxin
Adaptive Parthenocarpy
- plant produces SOME seedless fruits
- seedless fruits are called decoy fruits
Decoy fruit
- seedless fruit produced by a plant
- has more flesh than a seeded fruit, so predators eat seedless fruit instead
Giberellic acid produced by stem apical meristems
- synergetic with auxin
- promotes cell division
Giberellic acid produced from maturing embryo
- in fruit
- causes rapid movement of energy and nutrients from endosperm
- second step of germination
Cytokinins
- produced from root apical meristems
- moves upward
- antagonist to auxin
Cytokinins in roots
- causes cell elongation and inhibits branching
Cytokinins in stem
- inhibits cell elongation and induces branching
Abscisic Acid secreted by early embryo
- blocks production of giberellic acid
- secreted during stratification
Abscisic acid produced from root AM in response to dry soil
- turns off potassium pumps on guard cells and closes stomata to reduce water loss
Ethylene secreted by mature embryo
- causes fruit to ripen
Ethylene produced by ripening fruit
- induces synchronized ripening within community
- causes fruit abscission
- antagonistic to auxin
What does it mean to ripen?
- breakdown of starch to sucrose/glucose
- breakdown of sclereids
- breakdown of tanins
3 Approaches to Plant Defense
- Physical defense
- Mutualistic defense
- Chemical Defense
Physical defense
- thorns (stem)
- spines (leaf)
- trichomes
- waxy cuticles
Mutualistic Defense
- plant provides food
- animal provides protection
Chemical Defense
4 types
1. oils (citronella oils repel mosquitoes)
2. resins
3. tanins
4. alkaloids (caffeine, morphine, cocaine, nicotine)
- cost benefit tradeoff
2 Approaches to Chemical Defense
- constituent approach
- inducible approach
Constituent Approach
- produce and store high quantities of chemical at all times
- oils, resins, and tanins
- long living plants
Inducible Approach
- produce and store small amounts of chemical
- can produce rapidly in response to an attack
- alkaloids (mobile, polar, volatile)
- short lived plants, shade intolerant plants, pioneer species
Allelopathy
- plants secrete chemicals into the ground that block the germination of other plants
- ex: maple trees
