Lecture 7

Question 1

abiotic stressors

Answer 1

light, high temperature, water deficit, salt stress, cold, anaerobic stress, oxidative stress,

Question 2

adaptations for life is stressful environments

Answer 2

constitutive mechanists to tolerate or resist stress

Question 3

acclimation to stress

Answer 3

induced mechanisms to tolerate or resist stress

Question 4

example of stress adaptation

Answer 4

saguaro cactus is tolerant of water deficits due to morphology: barrel shaped photosynthetic stem, reduced surface area, stores water in barrel

Question 5

example of stress acclimation

Answer 5

spinach is tolerant to drought by accumulation of osmoprotective compounds which when produced reduce the water potential inside the plant cells reducing water loss down the gradient

Question 6

water deficit

Answer 6

caused by saline soils, cold or freezing temperatures, drought; low available water potential in soil

Question 7

response to water deficit

Answer 7

close stomata
regulate of stress response gene expression
accumulation of osmolytes and LEA proteins

Question 8

ABA and adaptation to stress

Answer 8

aba is involved in regulation of stomata opening and regulation of ABA-dependent stress response gene expression

Question 9

ABA stomata signalling pathway

Answer 9

1 Roots perceive low water potential
2 ABA is synthesized in roots and shoots
3 ABA travels in xylem to leaves
4 ABA is perceived by guard cells
5 Signaling
6 Stomata close

Question 10

ABA independent stomata opening process

Answer 10

phototropic receptors recognize blue light at sunrise and signal stomata to open

Question 11

LEA proteins (dehydrins)

Answer 11

late embryogenesis abundant proteins; hydrophilic, coat intracellular macromolecules to prevent aggregation of macromolecules as water level drops in cell, abundant during embryogenesis and seed maturation because seed maturation requires desiccation, mitigate low water levels by binding to water in water stressed plants;

Question 12

LEA proteins rice example

Answer 12

transgenic LEA rice grew well under water stress conditions compared to wt

Question 13

osmolyte accumulation in response to water stress

Answer 13

accumulation of compatible solutes to maintain water content even if water potential in soil drops; lowers water potential in cells allowing increased water uptake; some drought plants use this response very effectively

Question 14

compatible solutes

Answer 14

don’t interfere with cellular structure and function; inert

Question 15

osmolyte protective function

Answer 15

compatible solutes protect proteins, membranes, from build-up of physiologically damaging and denaturing ions during water deficit

Question 16

mechanism of desiccation resistance in resurrection plants

Answer 16

LEA proteins; osmoprotective sugars: 50% of hydrated plant weight is octulose which can quickly be turned into sucrose during dessication

Question 17

ROS

Answer 17

reactive oxygen species; produced during respiratory and photosynthetic electron transport, produced in response to stress, toxic, produced by reduction of molecular oxygen, reactive, strips electrons from biological molecules

Question 18

causes for ROS production

Answer 18

high light, extreme temperatures, ozone pollution, pathogen infection, drought, salinity,

Question 19

Ascorbate

Answer 19

vitamin C is a major antioxidant in plants; high concentrations in chloroplast, present in leaf apoplast

Question 20

RT-PCR

Answer 20

Reverse Transcriptase Polymerase Chain Reaction;
1 obtain mRNA from plant tissue
2 add RT to make cDNA of mRNA
3 add Taq polymerase to make second strand of cDNA
4 add gene specific primers and let Taq amplify specific cDNA
5 run gel electrophoresis and observe bands of specified cDNA

Question 21

SOD and APX

Answer 21

superoxide dismzutase and ascorbate peroxidase; antioxidant enzymes which when over expressed can increase tolerance to heat or cold induced oxidative stress

Question 22

Freezing damage:

Answer 22

ice crystals damage and kill cells–frozen water is unavailable causing drought conditions–freezing and thawing cycles block/interrupt xylem with air bubbles

Question 23

conifers conical or scale like leaves

Answer 23

conical or scale like leaves; shed snow, reduce surface area, thick waxy cuticle, retain leaves through winter allowing photosynthesis to begin immediately in spring

Question 24

conifers dehydrin LEA proteins

Answer 24

accumulate in leaves and trucks in winter, prevent aggregation and denaturation of macromolecules in cells

Question 25

conifers tracheids

Answer 25

adapted for efficient conduction of water even in dry/cold conditions– torus prevents air bubbles from flowing to next tracheid–water can still flow through other tracheas even in winter

Question 26

3 evolutionary solutions for angiosperms to fight cold

Answer 26

1 drop leaves seasonally, shut down water transport
2 thinner water conducting vessels and tracheas to reduce air bubble formation
3 overwinter as seeds or storage organs

Question 27

cork bark

Answer 27

reduces water loss in hot dry climates; full of Suberin (wax)

Question 28

xerophytes

Answer 28

likes dry conditions; needs little water; 2 types: succulents and non succulents

Question 29

succulent

Answer 29

stores water in various organs in cells with large vacuoles

Question 30

non succulents

Answer 30

various morphological features including small leaves, deep roots, thick cuticles, sunken stomata, many trichomes

Question 31

sunken stomata

Answer 31

trichomes line stomatal cavity and trap damp air creating microclimate limiting transpirational water loss in open stomata

Question 32

atmospheric bromeliads

Answer 32

tillandsia species; obtain water from atmosphere through modified trichomes

Question 33

torrey pine

Answer 33

pine species in sandy soil of San Diego desert; extensive long root system and obtain water from summer fogs that role in off coast through grooves in needles which condense water vapour and directs it down groove onto soil around trunk. produces its own rain

Question 34

flooding

Answer 34

too much water around roots results in oxygen deprivation or anaerobic stress

Question 35

aerenchyma

Answer 35

internal long distance gas transport pathways made up of cortical tissues that form gas filled spaces; constitutively formed in wetland species; formed by cell expansion and separation; surrounded by water-impermeable endodermis

Question 36

corn aerenchyma

Answer 36

acclimation; develops as a result of programmed cell death in root cortical cells in response to flooding

Question 37

adventitious roots

Answer 37

grow in response to flooding (O2 deprivation); grow at soil surface where oxygen levels are higher

Question 38

what stress tolerating traits would be beneficial to Ontario’s major crops for example soybeans?

Answer 38

drought tolerance due to the hotter and dryer summers

over-expressed SOD and APX antioxidant genes to cope with increasing air pollution especially near cities

Question 39

lithops

Answer 39

living stones; 2 succulent xerophyte leaves

Question 40

CAM plants

Answer 40

take in CO2 at night and store it until day time for photosynthesis reducing water loss because stomata are closed during the day,

Question 41

prickly pear cactus

Answer 41

shallow roots to collect water from fog

Question 42

air plants

Answer 42

live on other plants for support, they don’t have roots, they have

Question 43

blue agave

Answer 43

tequila plant; sunken stomata

Question 44

ponytail palm

Answer 44

succulent roots, water storage root above the surface, ponytail shaped

Question 45

spanish moss

Answer 45

tillandsia air plant grows on trees