Abiotic Interactions

Question 1

Main examples of primary abiotic affects on plant growth

Answer 1

light, water, CO2, O2, soil nutrient content and availability, temperature and toxins

Question 2

Define ideal plant growth conditions

Answer 2

conditions that allow the plant to achieve maximum growth and reproduction potential measured by components of total biomass

Question 3

Define stress

Answer 3

any environmental condition, abiotic or biotic, that prevent the plant from achieving full genetic potential (growth and reproduction)

Question 4

explain competition within plants/plant processes when under optimal growing conditions vs. when under stress conditions

Answer 4

optimal = minimal competition because can grow and reproduce where see fit
stress = competition present between reproduction and growth, where plants will likely use energy to reproduce even if not at full size

Question 5

Define annual vs. perennial plants

Answer 5

annual = plants that complete a life cycle in a single season
perennial = plants that have multiple seasons to produce seeds

Question 6

How would annual vs. perennial plants use their energy differently for growing and reproducing

Answer 6

annual plants would adjust to focus on reproducing as many viable seeds as possible
whereas perennial plants would adjust to ensure optimal storage of resources and enable surviving to the next season

Question 7

Define acclimation

Answer 7

improvement of a response with repeated exposure to a stress that is a non-permanent change that is epigenetic instead of genetically passed down

Question 8

Define adaptations

Answer 8

changes in a population over many generations due to natural selection that are heritable changes

Question 9

How does the stress, temperature, affect plants

Answer 9

increase temperature increases fluidity (and vise versa)
and fluidity disrupts the coupling between protein complexes resulting in reactive oxygen species that can cause cell damage

Question 10

What is plants most limiting resource, explain

Answer 10

water
97% lost to transpiration
1% used for metabolic processes (photosynthesis)

Question 11

Define water deficit

Answer 11

caused by intermittent to continuous periods without precipitation

Question 12

Define drought

Answer 12

term for a period of insufficient precipitation resulting in plant water deficit

Question 13

How does the stress, water deficit, affect plants

Answer 13

cell dehydration occurs and affect basic physiological processes (Ex. cell turgor)
also induces ABA accumulation which promotes stomatal closure, reducing water loss and gas exchange and inhibiting photosynthesis

Question 14

Define osmotic stress

Answer 14

due to salinity and results in water deficit symptoms

Question 15

Define cytotoxicity

Answer 15

toxic to living cells that results from accumulation of toxic ions interfering with nutrient uptake

Question 16

Define halophytes vs. glycophytes

Answer 16

halophytes = salt tolerant plants with genetic adaptations to saline conditions
glycophytes = plants not adapted to saline conditions that show growth inhibition and leaf discolouration

Question 17

How does the stress, salinity, affect plants

Answer 17

cytosolic Na increases and ions become cytotoxic and can cause protein degradation and membrane destabilization in the plant

Question 18

Explain the effects of salinity occurring in 2 phases

Answer 18

fast response = reduction in shoot growth, leaf expansion, and inhibition of lateral bud form
slow response = accumulation of toxic Na in leaves and inhibits photosynthetic and biosynthetic processes.

Question 19

What do extreme temperatures do to the plant

Answer 19

melt or harden RNA and DNA secondary structures which can cause protein buildup and degradation

Question 20

explain the effects of freezing temperature causing ice crystals

Answer 20

ice crystals can be lethal and likely form in apoplast because they have a higher freezing point.
ice crystals in apoplast decrease water potential causing the cell to become more negative and unfrozen water moves from the cell and causes plasma membrane to contract and pull away from the wall
plasma may become damaged and symplast loses 90% of osmotic active water

Question 21

how does the stress, flooding, affect plants

Answer 21

oxygen decreases in the roots because air in the soil is replaced by water.
causes less energy production and slowing of many processes resulting in acidification of cytosol and toxicity from ethanol accumulation.

Question 22

why should you not rapidly increase oxygen levels after flooding

Answer 22

because ROS will increase and can cause damage to plant root cells

Question 23

Define anaerobic stress and results

Answer 23

the absence of oxygen that can cause cell death within hours-days depending on the degree of genetic adaptation of the species

Question 24

Define light stress

Answer 24

occurs when high light intensity overwhelms capacity of photosynthetic machinery

Question 25

What do plants do to increase light capture

Answer 25

1. add more light harvesting chlorophyll units to PSII 2. increase number of PSII relative to PSI to enhance light capture and energy transfer

Question 26

How does the stress, high light, affect plants

Answer 26

overwhelms ability to convert energy into sugars and can results in producing ROS and causing cell damage

Question 27

How does excess UV radiation affect plants

Answer 27

disrupts photosynthesis, damages DNA, and induces formation of ROS

Question 28

How does the stress, heavy metals, affect plants

Answer 28

uptake and disrupt photosynthesis, mineral utilization, and enzymatic functions

Question 29

heavy metals can mimic _____

Answer 29

essential metal ions

Question 30

explain aluminum as an essential metal

Answer 30

it is a major component in soils but becomes toxic in acidic solutions and can cause stunted growth

Question 31

essential nutrients can be...

Answer 31

toxic and cause stress in excess

Question 32

explain the acclimation of a single stress vs. a combination of stresses

Answer 32

they can be different!

Question 33

Explain the difference in acclimation of heat on it's own vs. heat and drought

Answer 33

heat = increase plant stomatal conductance so leaves lose heat by open stomata and heat vs. heat and drought = stomata are closed to reduce lose of water and cause leaf temperature to increase

Question 34

explain the results of heavy metal or salinity with heat

Answer 34

enhanced transpiration (to cool down) could result in enhanced uptake of Na or heavy metals

Question 35

Examples of benefits of combinations

Answer 35

drought and ozone, ozone and UV, high CO2 and drought

Question 36

What is cross-protection

Answer 36

sequential exposure to different abiotic stresses that results in accumulation of the same general response proteins and metabolites and they persist after the stress conditions has reduced

Question 37

stress can cause signaling pathways to (sensing)

Answer 37

damage if not adapted, receptor activation to either phosphorylation or secondary messengers

Question 38

what developmental program is activated in response to stress

Answer 38

phenotypic plasticity

Question 39

What are the 5 main ways leaves show phenotypic plasticity to stresses

Answer 39

1. leaf structure 2. orientation 3. rolling 4. trichomes 5. waxy cuticles

Question 40

Explain how leaf structure/area changes in response to stress

Answer 40

flat for optimal surface for production of photosynthates and increase in surface area for evaporation and absorption

Question 41

Explain how orientation (and rolling) changes in response to stresses

Answer 41

parallel or perpendicular to sun to reduce damage also rolling and wilting of the leaves changes interception of radiation and reduces damage

Question 42

Explain how trichomes change in response to stress/display phenotypic plasticity

Answer 42

hair-like epidermal cells, can be densely packed and reflect radiation and reduce evaporation to keep leaves cooler however disadvantage is in pubescent leaves they reflect needed light for photosynthesis

Question 43

Explain how the cuticle responds to stress/ displays phenotypic plasticity

Answer 43

consists of a multi-layer of waxes and hydrocarbons on the epidermis that reflects light, restricts diffusion of gases and water, and deters pathogens

Question 44

Specifically, ____ structures are sensitive to stresses such as

Answer 44

protein structures temperature, pH, light, etc.

Question 45

Define molecular chaperone proteins

Answer 45

proteins that physically interact with other proteins to facilitate protein folding, reduce misfolding, and stabilize tertiary structures

Question 46

Define heat shock proteins

Answer 46

a unique chaperone protein type that synthesizes in response to many stresses. ex. to heat stress, they improve thermal tolerance that would otherwise be lethal

Question 47

Define late embryogenesis abundant (LEAs)

Answer 47

proteins that accumulate with response to dehydration during later stages of seed maturation.

Question 48

Define hydrophilins

Answer 48

a group of proteins with strong affinity for water and have molecular shielding which reduce aggregation of sensitive proteins

Question 49

Define dehydrins

Answer 49

proteins that accumulate due to stress, serve as molecular shielding and cryoprotectants

Question 50

____ and ____ can send distress signals to the _____ to influence stress responses

Answer 50

chloroplast and mitochondria nucleus

Question 51

What is the response of ABA hormone

Answer 51

most rapid response in drought conditions that controls stomatal closure and guard cell turgor

Question 52

when water is limited, ____ reduces before the _____ is affected

Answer 52

leaf expansion photosynthetic activity

Question 53

What regulates the shoot:roots ratio and how does it change with stress

Answer 53

ABA controls it it increase with roots growing at the expense of leaves

Question 54

Define osmotic adjustment

Answer 54

capacity for plants to accumulate solutes and use them to lower water potential during osmotic stress

Question 55

what are the two main ways of osmotic adjustment

Answer 55

one with vacuole and one with cytosol

Question 56

Explain the uptake of ions during osmotic adjustment

Answer 56

plants take up ions from soil mainly into vacuole, then other solutes accumulate in cytosol to maintain equilibrium between 2 compartments

Question 57

Define compatible solutes

Answer 57

organic compounds that are osmotically active in the cell but do not destabilize membranes or interfere with enzyme functions like ions do

Question 58

Define aerenchyma

Answer 58

tissue formed by root cells separated by prominent air-filled spaces in plants well adapted to wetland conditions

Question 59

What happens in the response to ROS accumulation during many stresses

Answer 59

they are detoxified by specialized enzymes and antioxidants (accept electrons from ROS and neutralize them) by ROS scavenging processes

Question 60

What are the 2 main ways to cope with toxic metals and metalloid ions and explain each

Answer 60

1. exclusion = ability of plants to block uptake of toxic ions preventing reaching toxic levels which involves the activation of plasma membrane and ion transport proteins 2. internal tolerance = biochemical adaptations that enable plants to tolerate, chelate, or compartmentalize with elevated concentrations of potential toxic ions (hyperaccumulation = internal tolerance to toxic ions, but rare)

Question 61

Define/explain supercooling

Answer 61

occurs during rapid freezing in protoplast when water remains liquid below its theoretical freezing point

Question 62

Define antifreeze proteins

Answer 62

specialized proteins that limit growth of ice crystals by binding to them to slow their growth