CHAPTER 31 PLANT RESPONSE TO INTERNAL AND EXTERNAL SIGNALS

Question 1

what are plant hormones?

Answer 1

chemical signals that modify or control one or more specific physiological process within a plant.

Question 2

what is tropism?

Answer 2

any response resulting in curvature of organs toward or away from a stimulus

Question 3

what is phototropism?

Answer 3

plant response to light observed that the grass seedling could bend toward light only if the tip of the shoot was present and exposed to light

Question 4

what are the main plant hormones?

Answer 4

auxin, cytokinins, gibberellins, abscisic acids, ethylene

Question 5

what is auxin?

Answer 5

produces in shoot tips and is transported down the stem, cell elongation, increasing the activity of proton pumps to loosen the cell walls including a lower ph activating expansions loosening the cell walls to grow longer

Question 6

what is cytokinins

Answer 6

stimulate cytokinesis, working together with auxin to control cell division and differentiation

Question 7

what is gibberellins?

Answer 7

many effects, seed germination and fruit growth

Question 8

what is abscisic acid?

Answer 8

contributes to seed dormancy, drought tolerance

Question 9

what is ethylene?

Answer 9

associated with apoptosis, triggers ripening fruit producers can control ripening by picking green fruit and controlling ethylene

Question 10

what is photomorphogenesis?

Answer 10

light triggering many key events in plant growth and development

Question 11

what is an example of a light receptor?

Answer 11

photochromes

Question 12

what is photochrome receptors?

Answer 12

exist in two reversible states with the conversion of Pr (photo red light) to Pfr )photo triggering many development responses

Question 13

red light

Answer 13

the conversation of Pr to Pfr sunlight increases the ratio of Pfr to Pr.
helps to flower, promote growth

Question 14

what is far-red light?

Answer 14

triggers the conversion of Pfr to Pr, Pfr reverts Pr in the dark.
captures more sunlight increase growth

Question 15

what is photoperiod?

Answer 15

the relative lengths of night and day, is the environmental stimulus plants use most often to detect the time of year

Question 16

short-day plant

Answer 16

plants that flower when a light period is shorter than a critical length. are governed by whether the critical night light sets a minimum number of hours of darkness.

Question 17

long-day plants

Answer 17

plants that flower when a light period is longer than a certain number of hours

Question 18

day-neutral plants

Answer 18

is controlled by plant maturity, not photoperiod

Question 19

critical night length

Answer 19

responses to photoperiod are actually controlled by the night length, not day length

Question 20

what is gravitropism

Answer 20

environmental stress due to gravity, shoots show negative gravitropism by growing upward
- plants may detect gravity by settling of STATOLTHS dense cytoplasmic components

Question 21

mechanism stimuli

Answer 21

gravity,light, movement, sun, touch

Question 22

thigmotropism

Answer 22

is the growth in response to touch

Question 23

environmental stress

Answer 23

stress can be abiotic (nonliving) flooding heat or biotic (living) pathogens