lesson 5

Question 1

plant sensory systems

Answer 1

-pigment molecules can absorb light and initiate a response
2 types of responses: Phototropism and photomorphogenesis

Question 2

phototropism

Answer 2

-directional growth response to light

Question 3

photomorphogenesis

Answer 3

nondirectional, light-triggered plant development
*phytochrome molecule
=phytochrome red Pr (inactive)
=phytochrome far-red Pfr (active)

Question 4

growth responses and phytochrome

Answer 4

-seed germination
-shoot elongation
-plant crowding

Question 5

seed germination

Answer 5

sunny conditions promote buildup of Pfr

Question 6

shoot elongation

Answer 6

etiolation-shoot elongation (slender and pale to conserve energy)

Question 7

plant crowding

Answer 7

plant height will increase quickly under shaded competition

Question 8

other light effects

Answer 8

-phototropism
-circadian clocks

Question 9

phototropism

Answer 9

-directional growth of stems
-phototropins 1 and 2 blue light receptors
-increase exposure to light for phtosynthesis

Question 10

circadian clocks

Answer 10

24 hr cycle rhythms
affect leaf position

Question 11

responses to gravity

Answer 11

gravitropism
amyloplasts

Question 12

gravitropism

Answer 12

response of plant to the gravitational field of the earth
roots bend toward center of gravity (positively gravitropic)
stems bend away from center of gravity (negatively gravitropic)

Question 13

amyloplasts

Answer 13

starch containing plastids
auxin: plant hormone

Question 14

responses to mechanical stimuli

Answer 14

-thigmomorphogenesis
-thigmotropism
-reversible responses to touch (turgor pressure, pulvini)

Question 15

thigmomorphogenesis

Answer 15

plants change form in response to mechanical stimuli

Question 16

thigmotropism

Answer 16

directional growth in response to contact

Question 17

responses to H2O and temperature

Answer 17

-extreme conditions may promote dormancy
-organ abscission
*abscission zone
*protective layer
*separation layer
-seed dormancy

Question 18

hormones and sensory systems

Answer 18

hormones are involved with plant function and development
*chemical signal
-8 major types
-Focus on
*auxin
*cytokinins
*ethylene
*abscisic acid

Question 19

auxin

Answer 19

-make cell walls soft to allow expansion
*stem elongation
-produced in shoot tip (apical meristem)
-many auxin forms
*synthetic auxin is used as herbicide

Question 20

cytokinins

Answer 20

-produced in root tip
-interacts with auxin (opposition)
*promotes cell division and differentiation
*promotes growth of lateral buds in shoots
*inhibits lateral root formation

Question 21

ethylene

Answer 21

-gaseous hormone
-promotes fruit development (ripening)
*breakdown of complex sugars
*chlorophyll degradation
*soften cell walls
*release of volatile compounds
-CO2 slows down fruit ripening

Question 22

abscisic acid-growth suppressant and dormancy

Answer 22

-helps maintain dormancy (buds and seeds)
-counteracts the effects of some other hormones (auxin and gibberellins)
-influences stomatal opening and closing)

Question 23

gibberellins

Answer 23

-class of 100+ hormones
-stem elongation (w/auxin)
-increased internode length
-flowering

Question 24

brassinosteroids

Answer 24

-appear similar to animal steroid hormones
-cell elongation (bending of stems)
-delayed senescence
-reproductive development

Question 25

oligosaccharins

Answer 25

-defense signaling -organ development

Question 26

strigolactones

Answer 26

-affect plant shape (w/auxin and cytokinin) -derived from carotenoid pigments -inhibit axillary buds

Question 27

transition to flowering

Answer 27

-phase change: process of becoming competent *juvenile phase *adult phase

Question 28

flower production

Answer 28

four genetically regulated pathways 1. light dependent (external cues) 2. temperature-dependent (external cues) 3. gibberellin-dependent (internal mechanisms) 4. autonomous pathway (internal mechanisms)

Question 29

light-dependent pathway

Answer 29

-photoperiodic response -short day plants and long day plants -facultative plants

Question 30

photoperiodic response

Answer 30

*24 hr cycle * adaptation to changing seasons

Question 31

-short day plants and long day plants

Answer 31

actually respond to amount of uninterrupted darkness

Question 32

facultative plants

Answer 32

photoperiod not absolute

Question 33

advantages of photoperiodic control of flowering

Answer 33

-ensures optimal abiotic conditions -synchronize with pollinator availability -may avoid competition for resources -utilized by commercial growers *photoperiod manipulation

Question 34

temperature-dependent pathway

Answer 34

vernalization: period of chilling -ensures flowering occurs after a cold period *better environmental conditons

Question 35

mechanics and regulation of light signaling

Answer 35

-gibberelin-dependent pathway -autonomous pathway

Question 36

gibberelin-dependent pathway

Answer 36

require increase in hormone levels

Question 37

autonomous pathway

Answer 37

-internal cues (nutrition important) -genetic factors common to all pathways