Lecture 6: Phytohormones and the Regulation of Stress Tolerance in Plants

Question 1

Phytohormones

Answer 1

Plant hormones: signalling molecules produced by plants that regulate various physiological process. These include growth, development, differentiation, responses to environmental stimuli

Question 2

Stress tolerance in plants

Answer 2

The ability of plants to withstand and adapt to adverse environmental conditions (drought, salinity, extreme temperatures, nutrient deficiency) without significant damage to their physiological and metabolic functions

Question 3

Auxins

Answer 3

Play a crucial role in promoting
-cell regulation
-tissue differentiation
-apical dominance

Involved in various aspects of plant growth (i.e. phototropism+gravitropism

Question 4

Ethylene

Answer 4

a gaseous hormone that regulates various physiological processes:
-fruit ripening
-senescence
-response to stress

Often associated with the plant’s response to environmental and developmental cues

Question 5

ABA (Abscisic Acid)

Answer 5

involved in plant responses to environmental stresses (particularly drought), regulates:
-stomatal closure
-water conservation

Question 6

Biosynthesis, Effects, Signaling Pathway: Auxins

Answer 6

Biosynthesis: Apical meristems, young leaves

Effects: Promote cell elongation, inhibit lateral bud growth, influence tropic responses

SP: involves activation of specific receptors, leading to changes in gene expression and cellular processes

Question 7

Biosynthesis, Effects, Signaling Pathway: Ethylene

Answer 7

Biosynthesis: produced in response to various stresses and during certain developmental stages (ACC synthesis and ACC oxidase)

Effects: fruit ripening, leaf sensescence, stress response

SP: involves a receptor-mediated pathway, leading to transcriptional changes and physiological responses (can be inhibited by acting on receptor 1-MVG or pathway AVG)

Question 8

Biosynthesis, Effects, Signaling Pathway: ABA

Answer 8

Biosynthesis: produced in response to particularly drought

Effects: induces stomatal closure, promotes seed dormancy, enhances stress tolerance

SP: involves receptors and a signal transduction pathway that regulates ion channels and gene expression

Question 9

Classes of Hormones

Answer 9

-Auxins
-Ethylene
-ABA
-Gibberellins
-Cytokinins
-Jasmonic Acid
-Salicylic Acid

Question 10

Hormone Biosynthesis: Isoprenoid Pathway

Answer 10

Isopentenyl diphosphate:
-Cytokinins
-Brassinosteroids, Gibberellins, ABA, Strigolactones

Question 11

Hormone Biosynthesis: Amino Acids

Answer 11

1. Tryptophan: IAA
2. Methionine: Ethylene
3. Arginine: Polyamines

Question 12

Hormone Biosynthesis: Lipids

Answer 12

Linolenic acid: Jasmonic Acid

Question 13

Stress

Answer 13

Any factor that prevents the plant from achieving its full genetic potential
-can be biotic or abiotic.

Question 14

Acclimation

Answer 14

Homeostatic adjustment in response to changing environmental factors (reversible, metabolic, epigenetic)

Question 15

Adaptation

Answer 15

-Tolerance/Avoidance
-associated with permanent changes in the genome (IRREVERSIBLE)

Question 16

Strain

Answer 16

reaction inside a system. the magnitude can be a function of the duration of stress:
-return to

OLD: Elastic
NEW: Plastic
FAILURE: Collapse of homeostasis

Question 17

Osmoregulation

Answer 17

-when faced with water scarcity, plants regulate their internal osmotic pressure by accumulating compatible solutes (sugars, proline, etc.)

-Helps the cell maintain turgor pressure (needs to be positive otherwise plant will wilt): prevents water loss+dehydration

SUSTAINS cell structure and etc even with reduced water availability.

Question 18

Drought tolerant crops

Answer 18

-Corn: Traditional plant breeding
-Introduction of a transgenic trait: NGET
-ABA and drought: role in response to abiotic stress