Lecture 11:Physiology II Flashcards
Types of water potential are
additive
Water flows along water ____
water potential gradients: water will move from higher water potential to lower water potential
-ve attracting, +ve repelling
pure water= 0 Mpa dry air=-100 Mpa
water will move from pure water to air
Gravimetric water potential (gravitational)
height increases water potential
Ex. height increases water potential and water will move back down to lower water potentials
Osmotic water potential
increasing salinity decreases water potential
saltier means you have lower water potential and water will want to move in to decrease the salinity
Matric water potential
energy associated with attractive forces on surfaces of large molecules inside cells or on surfaces of soil particles
Increasing matric forces decreases water potential
Hydrostatic water potential (hydrostatic pressure, pressure potential, turgor potential)
High pressure increases water potential
water inside cell has strength for pressure and makes water want to move out
Photosynthesis for water balance in plants
Open stomata for CO2 to come in and make sugars for the start of photosynthesis
Water beings evaporating out of these cells
As losing water, creates water potential gradient for water to move from soil to air
Water moves toward
lower water potentials
When soil is dry,
water potentials decrease in plants and may cause damage
stomata can shut to stop losing water
damage can sometimes be repaired
since water potentials decrease, harder for water to move through water potential as plant has to be even more negative to get water to move through
Critical water potential: plants shut stomata when no rain causes
decreases transpiration and sacrifice photosynthesis to protect the xylem
Adaptations of terrestrial plants to dry soils (water relations)
Try to get more water out of the soil
Higher concentration of organic solutes to try to pull more water out of the soil
More root hairs to forage better within the soil to pull water out
Protecting roots: shed small roots during drought
deep roots: searching for other water sources:
Grow only in wet season
Close stomata
Store water (succulents)
Small leaves have less boundary layer and would be cooler, so evaporation is slower OR thick boundary layer so air next to plant is more humid
Water balance in microorganisms
Mostly iso-osmotic (similar water potential) to environment
Challenges environments for water balance in microorganisms
Estuaries, tide pools, saline lakes are constantly changing in salinity; cause a lot of change in the organisms –> spend energy on osmotic adjustment and changing solute concentration
Very dry environments for microorganisms
Difficult for microbes as much of terrestrial microbial activity is enhanced by water availability
Water balance in animals
movement, eating, drinking —-> greater control
Fish (teleosts): marine fish environment
Marine fish are hypoosmotic to (less salty than) the environment
Fish (teleosts): freshwater fish environment
Freshwater fish are hyperosmotic to (more salty than) the environment
Fish want to maintain their
salinity
less salty than the water in marine environments
more salty than water in fresh water
Fish have adapted behaviors and physiologies that help them slow the
natural movement of water
into their bodies (in fresh water)
out of their bodies (in salt water)
Terrestrial animals use skin as
barrier to water loss but prevents gas exchange with environment
Amphibians rely on
stable water supplies
Some organisms are desiccation tolerant meaning
ability of organism to survive and regain function after losing almost all of its water and drying out
What are the categories of energy in photosynthesis in terrestrial plants
C3 photosynthesis: most plants
C4 photosynthesis: corn, sugar cane, other warm climate grasses, few forbs, very few woody plants)
CAM (many succulents)
C3, C4, CAM are named for their difference in
first C compound made from CO2 and more important differences in timing/location of CO2 uptake from atmosphere and Calvin cycle
C3 photosynthesis: 3PG (phosphoglycerate 3C’s)
C4 photosynthesis: OAA (oxaloacetic acid: 4C’s)
CAM photosynthesis: malic acid and OAA
Rubisco
enzyme that is apart of productive Calvin cycle in taking CO2 to produce O2 and unproductive Photorespiration cycle in take in O2 and produce CO2
Low temperatures, Rubisco and photosynthesis more
High temperatures, Rubisco does Photorespiration
Photorespiration
inefficiency of photosynthesis with Rubisco
unproductive breakdown of things we are trying to build within the cell
process where rubisco uses oxygen instead of carbon dioxide during photosynthesis, leading to release of carbon dioxide and loss of fixed carbon
Photorespiration dependent on
relative percent of O2 vs. CO2
Higher CO2 concentration decreases photorespiration
(Lower O2 concentration increases photorespiration)
Lower CO2 increases photorespiration
(Higher O2 increases photorespiration)
Higher temperatures increase efficiency of O2 uptake and increase photorespiration
Is C4 or C3 better at high temperatures?
C4
Carbon moves through:
stomata –> mesophyll cells –> bundle sheath cells –> phloem
C3 photosynthesis
mesophyll cells have Calvin Cycle
Photosynthesis directly with CO2
C4 photosynthesis
bundle sheath cells (across waxy boundary) have Calvin cycle
builds up C concentrations before starting Calvin cycle
brings in CO2 into mesophyll cell and packs carbon into C4 which is broken back into CO2 to then run Calvin Cycle
C3 plants include
most northern grasses, most trees, shrubs
Ex. rice, wheat, cheatgrass
C4 plants include
mostly tropical and subtropical grasses, including most central TX grasses
Ex. corn, sugarcane, little bluestem
C4 photosynthesis decreases
photorespiration dramatically
Calvin cycle is moved to different cell and not exposing Rubisco directly to raw air with lots of oxygen compared to C3
Costs of C4 photosynthesis
Costs additional ATP
C4 not as beneficial at low temp and low light levels
Would be costly to switch back and forth: different cells have Calvin cycle so plants are either C4 OR C3 entirely
If C4 benefits do not outweigh the costs over whole year, becomes
unfavored (in comparison to C3)
We can infer ___ from ____ ratios of C3 and C4 plants
diets
isotope
Which has less 13C: C3 or C4
C3 (more negative %)
δ13C of tissues of a terrestrial animal tells us about
ratio of C3:C4 plants in diet
Question: what does δ13C of modern US: -16.4 and modern UK: -21.7 tell us about diet?
UK has more negative % so UK eat more C3 plants
USA has more positive % so US eat more C4 plants
How do C3 and C4 vs. CAM photosynthesis differ
Timing of CO2 uptake
C3 and C4 photosynthesis open stomata during day
Cam photosynthesis: open stomata at night and store carbon dioxide at night and fix during day
CAM photosynthesis (crassulacean acid metabolism)
Strategy for water conservation
Open stomata at night to lose less water- when air is humid
Run Calvin cycle during day
Common in arid/dry environments
Seen in tropical epiphytes (plants growing on plants)
Ex. Prickly pear, Agave, Pineapple
Plants can switch between C4 and CAM why?
Plants can be facultative in switching between the two when favorable
How do you think climate change (increasing CO2 and temperature) might influence the abundance of C3, C4, and CAM plants
Note that greater CO2 and lower temperatures decrease water limitation
Photosynthesis Type C3:
Better in __ CO2 concentrations
Better in ___ temperatures
Photosynthesis Type C4
Better in __ CO2 concentrations
Better in __ temperatures
Photosynthesis Type CAM
Better in __ CO2 concentrations
Better in __ temperatures
C3: Average, Average
C4: lower (build up Carbon concentration before Calvin cycle) , higher (lower photorespiration)
CAM: lower (since able to store in CO2 in stomata during night), higher
Heterotrophs
Organism that consumes other plants and animals for energy and nutrients
Does not make energy themselves
Tradeoffs for heterotrophs
Detritus abundant but low in useful compounds and nutrients
Living prey difficult to find and catch, but great to eat
Plants easy to find but less energy rich –> herbivores generally have to eat more volume than carnivores
Heterotrophs have many adaptations to
particular food sources
Ex. beaks for cracking seeds, humming birds with long flower tubes to access nectar, mosquito with straw mouth to pierce skin and suck blood, skimmers pick up fish with beak shape
Herbivores have much longer digestive tracts due to
They eat food low in nutrients and need lots of time to try to get those nutrients unlocked and broken down from the power quality food
Examples of how heterotrophs use tools for their benefit
Dolphin picks up a sponge from the environment protect their noses (rosta) while they poke at the floor to find fish
