F ... 24 - Plant Hormones

Question 1

plant hormones act in __ concentrations.

Answer 1

very low (10^-6 M or below)

Question 2

plant hormone pathway

Answer 2

synthesized in one tissue, transported, acts in another

Question 3

plant hormones regulate ___

Answer 3

many aspects of dev

Question 4

Hormones rarely __

Answer 4

act alone.

Question 5

five classic hormones

Answer 5

1. auxin
2. cytokinin
3. ethylene
4. abscisic acid
5. gibberellin

Question 6

“new” hormones

Answer 6

brassinosteroids - growth / expansion
jasmonic acid, salicylic acid - defense
strigolactones - branching

Question 7

auxin

Answer 7

POLAR transport from shoot tip. (apical dominance)
controls cell elongation / division, fruit dev.
several tropisms

Question 8

how does auxin growth (elongation) occur?

Answer 8

“loosening” of cell wall via proton pump

Question 9

auxin suppresses ___

Answer 9

lateral branching

[high} = vertical growth
[low] = removed tip... branching occurs

Question 10

auxin transport is unique among hormones because…?

Answer 10

specifically protein mediated… cellular influx / efflux

occurs in parenchyma, shoot tip downward

Question 11

auxin agricultural uses

Answer 11

herbicide (2,4-D)

tissue culture propagation

Question 12

Auxin:Cytokinin ratio in culture propagation…

Answer 12

determines differentiation.

high (A:C) - roots
low (A:C) - shoots
= - callus

Question 13

cytokinins

Answer 13

promotes cell div (formed in roots, up thru xylem)
delays senescence
organogenesis
sink/source
vascular dev

Question 14

ethylene

Answer 14

smallest hormone (gas)
fruit ripening
abscission of leaves
growth (triple response)
inhibits cell expansion

Question 15

ethylene’s triple response in seedlings

Answer 15

1. hypocotyl length
2. hypocotyl width
3. apical hook

Question 16

ABA

Answer 16

abscisic acid

Question 17

abscisic acid

Answer 17

dormant tissues, growth inhibitor
produced in response to stress
causes stomatal closure
NOT involved in abscission!

Question 18

Why is ABA important in stressful conditions?

Answer 18

increases resp… prevents premature germination of seeds in cold, drought, water/salt stress conditions.

Question 19

GA

Answer 19

gibberellic acid

Question 20

gibberellic acid

Answer 20

many compounds, few active… produced in shoot apex
dramatic stem growth
enzymatic breakdown of starches during germ

Question 21

GA discovered with…

Answer 21

Foolish rice disease

Question 22

GA in plant development

Answer 22

stem elongation
seed storage breakdown… dev / germ
promotes fruit set and parthenocarpy
flowering in long day plants

Question 23

parthenocarpy

Answer 23

seedless fruit

Question 24

brassinosteroids

Answer 24

growth stimulator (internode elongation) from pollen (500 lbs!)

Question 25

jasmonic acid (JA)

Answer 25

stimulates: defense against pathogens, wound response, ripening
inhibits: seed/pollen germ, root growth

Question 26

SA

Answer 26

salicylic acid

Question 27

JA

Answer 27

jasmonic acid

Question 28

salicylic acid

Answer 28

disease resistance, flowering induction

Question 29

strigolactones

Answer 29

produced from carotenoids, shoot branching

striga

Question 30

hormone perception / signaling

Answer 30

1. hormone binds to receptor
2. signal
3. binding / activating hormone regulated genes

Question 31

varied effects of hormones

Answer 31

1. interaxn with other hormones / signals
2. amount
3. sensitivity of tissue to hormone
4. condition of plant ( age / stress )