Plant hormones

Question 1

hormones

Answer 1

signaling molecules carry info from cell to cell

Question 2

Auxins

Answer 2

lengthen shoots and apical dominance

• decrease abscission/leaf dropping
• fruit formation

Question 3

Ethylene

Answer 3

ripen fruit (is a gas)

Question 4

ABA

Answer 4

Abscisic Acid – induce dormancy
- drought tolerance by
closing stomata

Question 5

Positive feedback loop with fruit ripening

Answer 5

one fruit ripens 
ethylene gas released into air 
recieved by other fruits near by 
other fruits ripen 
increase stimuli 
repeat

Question 6

seed dormancy

Answer 6

mature seed produces ABA
1. induces production of proteins to resist dehydration
2. induce seed dormancy
(Stop growing, block mitosis, uses way less energy)

Question 7

in order to germinate (get out of dormancy)

Answer 7

ABA levels must come down

1. heavy rain washes ABA out of seed
2. light and cold exposure may also be needed

Question 8

Auxin concentrations control

Answer 8

gene transcription (what gene is activated)

Question 9

genes controlled regulate

Answer 9

cell differentiation

Question 10

Auxin only produced in the

Answer 10

apical meristem

Question 11

Auxin is transported down the shoot by

Answer 11

Polar transport (much faster than diffusion)

Question 12

Apical meristem =

Answer 12

tip of root/shoot that is growing : doing mitosis

Question 13

why is auxin mechanism polar

Answer 13

Polar because auxin transport proteins are only located at the base of the cells.
(at one pole

Question 14

Acid Growth

Hypothesis

Answer 14

High concentration of Auxin cause elongation of apical cells (growth)

Question 15

why called acid growth hypothesis

Answer 15

Called Acid Growth because high Auxin conc. causes protein pumps to actively transport H+ out of the cell (making the cell wall low pH)

Question 16

Effects of high H+ conc. in cell wall

Answer 16

Membrane potential created (voltage across memb.)
Memb. Pot. Induces ion uptake by cell
Cell becomes hypertonic
Osmosis increases turgor pressure
Low pH
Activates expansin :

Question 17

expansin

Answer 17

Enzymes that break crosslinks (H-bonds) btwn cellulose fibers
Allows cell wall to expand

Question 18

cell growth based on light

Answer 18

Under uniform light cells grow equally

Directional light causes dark side cells to elongate more