Abiotic Stess

Question 1

Phases of stress

Answer 1

Alarm phase
Recovery phase
Hardening phase (acclimation)
Exhaustion phase

Question 2

Adaption

Answer 2

A genetically determined level of resistance acquired by a process of selection of many genes

Question 3

HD START protein

Answer 3

Homeodomain START transcription factor

Deeper more lateral roots, reduced stomatal density, higher abscisic acid, resistance to oxidative stress

Question 4

Stress resistance mechanisms

Answer 4

Avoidance
Tolerance
Acclimation

Question 5

Drought resistance mechanisms

Answer 5

Desiccation postponement (tissue hydration maintained)
Desiccation tolerance (function while dehydrated)
Drought escape (complete lifecycle in wet season)

Question 6

Water deficit

Answer 6

Water content of a tissue or cell that is below the highest water content exhibited in the most hydrated state

Question 7

Lines of defense against drought

Answer 7

Decreased leaf area
Deeper root growth
Stomatal closure (hydropassive/hydroactive)

Question 8

Water deficit inhibits photosynthesis

Answer 8

Dehydrates mesophyll cells and impairs metabolism

Question 9

Comparable solutes

Answer 9

Neutrally changed at physiological pH
Don’t interfere with enzyme function
Proline, glycine betaine

Question 10

Cooling strats

Answer 10

Paraheliotropism/diheliotropism
Reflexive wax
Leaf size

Question 11

ABA stress responsive genes

Answer 11

Osmoprotectants
Oxidative stress responses (peroxidase)
Movement of water and ions (aquaporins)
Membrane and protein stabilization (LEAs)

Question 12

LEA proteins

Answer 12

Late embryogenesis proteins
Protects cell membrane (prevent crystallization of important molecules during desiccation)
Hydrophilic

Question 13

Temperature compensation point

Answer 13

Temp at which amount of CO2 fixed by photosynthesis equals the amount of CO2 released by respiration in a given time

Question 14

Signaling pathways for thermotolerance

Answer 14

ABA and SA signalling
Ethylene biosynthesis
Calcium signalling

Question 15

Chilling injury

Answer 15

Disrupts starch conversion to sugars
Less CO2 exchange
Less photosynthesis
Destruction/degradation of chlorophyll

Question 16

Chilling causes

Answer 16

Increased amount of desaturase enzymes

More unsaturated fats

Question 17

Ice nucleation

Answer 17

Process by which water molecules form a stable ice crystal

Question 18

Dehydration

Answer 18

Water moves from protoplast to extracellular ice

Question 19

Antifreeze proteins

Answer 19

Bind to ice surface to slow or prevent more ice formation

Thermal hysteresis proteins

Question 20

Sodicity

Answer 20

High Na+ content
Injures plants
Degrades soil structure

Question 21

Salinity

Answer 21

Determined by electrical conductance

Question 22

Osmotic effects of salt stress

Answer 22

Low osmotic potential

Less soil water potential

Question 23

Salinity vs soil desiccation

Answer 23

Total amount of water available

Question 24

Salt stress and ion toxicity primary effects

Answer 24

Na+, Cl-, SO4 2- accumulate in injurious concentrations
Deactivate enzymes
Plant membrane stability affected
Photosynthesis inhibited

Question 25

Salt stress and ion toxicity secondary effects

Answer 25

Disruption of cell membrane integrity

Cell death

Question 26

Salt reduction strats

Answer 26

Casparian strip - ion movement restriction into xylem
Actively extrude Na+ into xylem
Specialized salt glands on leaf surface
Adjustment of water potential
Changes in gene expression

Question 27

Toxic trace element adaption

Answer 27

Exclusion
Internal tolerance
Hyperaccumulation (protection against herbivory)