Bio 304 Plant Exam Ii

Front 1

What are three common plant hormone responses?

Back 1

Auxin, gibberellins, ethylene

Front 2

What are three types of plant movements?

Back 2

Tropisms, nastic movements, and phytochrome-mediated responses

Front 3

What is the definition of a plant hormone?

Back 3

an organic compound produced at one site that regulates function at another site

Front 4

What are the five categories of plant hormones?

Back 4

auxin
gibberellins
cytokinins
abscisic acid
ethylene

Front 5

Know that there five characteristics of hormones make them difficult to study.

Back 5

-small conc.s make detection difficult
-effects vary from plant to plant
-slight changes in conc. cause different responses
-hormones interact with each other
-hormones activate genes

Front 6

What was the first identified hormone?

Back 6

Auxin was the first identified hormone, by Fritz Went

Front 7

Auxin causes ________ by _______.

Back 7

Auxin causes bending toward light by differential transport of chemicals from lighted side of plant to shaded side.

Front 8

What is the structure of auxin?

Back 8

an organic acid, IAA, or indole-3acetic acid

Front 9

How many forms of auxin are there?

Back 9

There are two synthetic auxins (2,4-D, NAA) and only one known naturally occurring auxin

Front 10

What kind of transport do auxins have?

Back 10

unidirectional (polar) in parenchyma, down shoots, up roots,
and nonpolar transport in phloem

Front 11

What is phototropism?

Back 11

a positive response to unidirectional light

Front 12

What happens when a leaf or fruit undergoes abscission due to a change in auxin?

Back 12

Normal leaves have high levels auxins which inhibits the abscission zone, a damaged leave has lowered auxin synthesis, and short days and cool nights cause ethylene production which blocks auxin synthesis.

Front 13

What does auxin do in regard to roots?

Back 13

auxin causes induction of adventitious roots

Front 14

What does very high concentrations of auxin (as an herbicide) cause?

Back 14

stimulates ethylene synthesis which can cause: epinastic growth (leaf curling and bending of shoot tips, eventual abscission of leaves and death of plant)

Front 15

What does epinasty mean? What causes it?

Back 15

epinasty is the downward curvature of a leaf, leaf part, or stem resulting from more rapid growth on the upper side of a petiole than the lower side in reaction to ethylene

Front 16

What does auxin do to some fruits?

Back 16

causes parthenocarpic(seedless) fruits in tomatoes, cucumbers, eggplant, strawberries

Front 17

What is auxin used for in tissue culture?

Back 17

root induction

Front 18

What are the sites of synthesis of gibberellins?

Back 18

young. actively dividing tissues, seeds

Front 19

Where are gibberellins in?

Back 19

both x and p

Front 20

What are four effects of gibberellins?

Back 20

1) hyperelongation of some plants (by both cell division and enlargment)
2) normal growth of dwarf varieties
3) regulates production of hydrolytic enzymes in seeds of cereals- initiates germination
4) parthenocarpic fruits (grapes, mandarin oranges, peaches and other plants not affected by IAA)

Front 21

What is cytokinesis?

Back 21

cell division

Front 22

What do cytokinins stimulate?

Back 22

cell division and shoot development in plant tissue cultures

Front 23

What is the site of synthesis of cytokinins?

Back 23

primarily root tips

Front 24

How are cytokinins transported?

Back 24

x (roots to shoots)

Front 25

What are the four effects of cytokinins?

Back 25

1) promotes cell division
2) shoot development in undifferentiated callus tissues
3) delays leaf senescence
4) counteracts inhibitory effects of IAA in apical dominance

Front 26

What is abscission?

Back 26

the process by which a plant intentionally drops one or more of its parts, such as a leaf, fruit, flower or seed

Front 27

What are the sites of synthesis for Abscisic acid?

Back 27

mature leaves, seeds

Front 28

How is abscisic acid transported?

Back 28

from leaves in P; from roots in X

Front 29

What are the two affects of abscisic acid?

Back 29

1) induction and maintenance of dormancy in seeds and buds
2) stomate closure

Front 30

What is ethylene's structure?

Back 30

a hydrocarbon gas

Front 31

What is the site of synthesis of ethylene?

Back 31

in any tissues experiencing physiological stress; ripening fruit

Front 32

How is ethylene transported?

Back 32

by diffusion from site of synthesis

Front 33

What is the effect of ethylene?

Back 33

fruit ripening, induces senescence and abscission

Front 34

What does endogenous mean?

Back 34

produced, originating or growing from within

Front 35

Is a plant's circadian response endogenous or a environmental response?

Back 35

endogenous ( not under external control but rather controlled by an internal clock that can be adjusted or "set" by external stimulii)

Front 36

What are tropisms?

Back 36

responses to environmental stimuli in which the direction of the response depends on the direction from which the stimulus is detected

Front 37

What are mastic movements?

Back 37

responses which are independent of the direction from which stimulus comes

Front 38

What is phototropism and what is its mechanism?

Back 38

movement of shoot apices toward lights; IAA is transported away from lighted side in response to blue light

Front 39

What is gravitropism?

Back 39

response to the pull of gravity- roots have a positive response and shoots have a negative response

Front 40

How does gravitropism work?

Back 40

occurs in root and shoot apices

special starch-containing plastids called amyloplasts (pr statolithes) may be involved, and IAA is thought to be involved

Front 41

What is thigmotropism?

Back 41

response to touch, usually +

Front 42

What hormones are involved in thigmotropism?

Back 42

IAA and ethylene

Front 43

What are thigmonastic movements?

Back 43

responses to touch but not in the direction towards or away from the touch; direction of movement always the same

Front 44

What are nyctinastic movements?

Back 44

sleep movements, nightly movements of leaves in many plants, esp. legumes

Front 45

What are photoperiodic responses?

Back 45

responses to changes in light-dark cycles

Front 46

What is the importance of photoperiodic responses?

Back 46

they enable plants to respond to seasonal environments

Front 47

What is an example of photoperiodic responses?

Back 47

flowering

Front 48

What are the three kinds of 'day' plants and their needs for flowering?

Back 48

Long-day plants: require lengthening days to flower
Short-day plants: require shortening days to flower
Day-neutral plants: flower whenever they mature regardless of the season

Front 49

The basic response to photoperiod is regulated by a receptor called _______.

Back 49

phytochrome

Front 50

T/F: plants that respond to daylength are not influenced with other factors (temp., state of development, etc.)

Back 50

F. frequent daylength is coupled with other factors

Front 51

Where are phytochromes found?

Back 51

not localized at site of flowering but found in all plant tissues (including roots)

Front 52

Which factor is more critical: length of light period or length of dark period?

Back 52

length of dark period

Front 53

What is the wavelength (color) required to cause a photoperiodic response?

Back 53

red, but any response stimulated by red light is inhibited by a subsequent exposure to far-red light- suggesting the existence of a reversible switch that depends on the wavelength striking it last

Front 54

What are the two forms of the photochrome receptor?

Back 54

Pr, which is sensitive to red light and Pfr that is sensitive to far-red light

these are convertible
Pfr causes red light responses
Pfr also convert back to Pr in the dark (which allows plant to tell the length of the dark period)

Front 55

What is the structure of phytochromes and how do they work?

Back 55

both forms of phytochrome are a molecule that consists of a light-absorbing chromophore attached to a large protein
the chromophore changes structurally when it absorbs light energy