Plant Responses to the Environment - Hormones

Question 1

what to the physiological effects of hormones depend on (5)

Answer 1

• hormone concentration
• tissue type
• tissue age
• presence of other hormones
• environment

Question 2

mixing of hormones results in… (2)

Answer 2

• wide range of effects

- can differentiate concentrations and tissue location

Question 3

what physiological processes are regulated by gibberellins (3)

Answer 3

• seed germination
• cell elongations (with auxins)
• flowering

Question 4

seeds

Answer 4

• structures that protect the embryo and serve as energy source for the seedling upon germination

Question 5

components of seed (4)

Answer 5

• aleurone
• endosperm
• embryo
• seed coat

Question 6

seed aleurone

Answer 6

• source of amylase enzyme used to break down starch into sugars

Question 7

seed endosperm

Answer 7

• surrounds the embryo and store energy in the form of starch and other nutrients

Question 8

seed embryo (2)

Answer 8

• the multicellular organism before it emerges from the seed

- source of gibberellins

Question 9

seed coat

Answer 9

• semi-hard covering that creates a barrier between environmental factors and the embryo

Question 10

what are the requirements of seed germination (5)

Answer 10

• rehydration
• oxygen
• suitable temperature
• remobilization of energy reserves
• facilitated by red light (Pfr)

Question 11

how does Pfr affect germination

Answer 11

• increases the amount of GAs

Question 12

how does Pr affect germination

Answer 12

• decreases the amount of GAs

Question 13

what does abscisic acid regulate

Answer 13

• multiple plant responses to stress, including seed dormancy and stomatal closure

Question 14

when does ABA interfere with the germination pathway by GA (3)

Answer 14

• ABA inhibits synthesis of amylase in the aleurone layer
• no nutrients are available for germination
• germination is delayed

Question 15

how does ABA control stomatal closure (2)

Answer 15

• ABA synthesized in the roots in response to stress (dehydration) will travel using xylem and promote stomatal closing
• the roots are the first to detect lack of water

Question 16

how does ABA affect the solute potential of stomatal guard cells

Answer 16

• makes it less negative

Question 17

senescence (3)

Answer 17

• involves degradative biochemical processes and leads to death
• can be triggered by the environment or as a natural response to aging
• associated with low accumulation of CKs in leaf tissue

Question 18

seasonal senescence (2)

Answer 18

• plant decides when leaves are not worth it to be maintained
• leaves senesce to make better use of the nutrients

Question 19

sequential senescence (2)

Answer 19

• older leaves that are not as efficient are killed

- nutrients are used for younger tissue

Question 20

what will result from treatment of senescing leaves with cytokinins (2)

Answer 20

• delayed senescence

- leaves stayed greener for longer

Question 21

ripening (2)

Answer 21

• transition of fruits from physiological maturity to senescence
• facilitates reproduction by facilitating seed dispersal and preparing the seed-bearing organ for detachment from the plant

Question 22

stages of ripening (3)

Answer 22

• cell division until the right amount of cells is achieved
• cell expansion until the right size is achieved
• ripening

Question 23

climacteric fruit (2)

Answer 23

• ethylene-dependent fruits; require ethylene for production

- can ripen after harvesting

Question 24

non-climacteric fruits (2)

Answer 24

• ethylene-independent fruits; require ABA, and not ethylene, for production
• only ripens in the plant

Question 25

ethylene (4)

Answer 25

• simplest structure of all plant hormones
• gaseous, non-polar, hydrophobic molecule that freely diffuses across the plasma membrane
• production is autocatalytic
• activates multiple aging-related processing

Question 26

how is ethylene autocatalytic (2)

Answer 26

• production is linked with a respiratory burst
• once the hormone levels reach a threshold level, it is able to activate its own synthesis; presence of ethylene activates synthesis of more ethylene

Question 27

what age-related processes does ethylene activate (3)

Answer 27

• ripening, senescence, abscission

Question 28

abscission

Answer 28

• separation of the organs from the plant

Question 29

to avoid premature ripening, what conditions would you store fruit

Answer 29

• to avoid respiratory bursts: high CO2/low O2 concentrations

Question 30

what will result from placing two ripening fruits next to each other

Answer 30

• acceleration of ripening of both fruits

Question 31

ethylene promotes fruit ripening by enhancing the expression of: (4)

Answer 31

• chlorophyll degradation enzymes
• fruit softening enzymes
• fruit sweetening enzymes
• senescence associated genes