Plant Responses To Internal And External Signals

Question 1

Etiolation

Answer 1

Morphological adaptions for growing in darkness; no green tissue being produced

Question 2

De-etiolation

Answer 2

when exposed to light, shoots and roots begin to grow normally

Question 3

Plant hormones

Answer 3

Coordinate growth, development and stimuli; ex: Auxin, Abscisic Acid, Cytokinin, Ethylene, Giberellins; produced in low concentration

Question 4

Tropism

Answer 4

Any response resulting in curvature of organs towards or away from a stimulus

Question 5

Significance of a tip of a plant.

Answer 5

The tip is the most responsible in absorbing light; therefore it determines curvature due to wanting light

Question 6

How did they conclude tip determines curvature?

Answer 6

Darwin and Darwin conducted an experiment:

No tip on plant/tip removed: no bending

Opaque Cap; no bending

Transparent Cap: bending

Opaque shield over curvature: bending (tip is not covered)

Question 7

Auxin

Answer 7

Refers to any chemical that promotes enlongation of coleoptiles; stimulates proton pumps in plasma membrane -> lower pH -> activate expansins (enzymes that loosen walls fabric and allowing cell to expand

Question 8

What causes apical dominance

Answer 8

Auxin flow from the shoot of a branch simulates growth in lower branches

Question 9

Cytokinins

Answer 9

Produced in actively growing tissues (roots, embryos, and fruits); work together w/ auxin to control cell division and differentiation; cytokinins, auxin, and strigactone interact in apical dominance

Question 10

Gibberellins

Answer 10

Growth promoting hormone that affects stem enlongation, fruit growth, and germination; produced in young organs; stimulate growth of cells and stems

Question 11

Which two hormones have to be present for fruit to develop?

Answer 11

Auxin and gibberellins

Question 12

What does the release of gibberellins do?

Answer 12

Signals seeds to germinate and endosperm to break down

Question 13

Abscisic Acid

Answer 13

Plays a role in seed dormancy; seed will only germinate in optimal conditions; ABA removed via rain, light or prolonged cold=dormancy broken; causes stomata to close rapidly when losing water (drought)

Question 14

Ethylene

Answer 14

Produced in response to stresses like drought, flooding, mechanical pressure, injury and infection

Question 15

Name 4 Effects of Ethylene

Answer 15

Mechanical stress, senescence, leaf abscission, and fruit ripening

Question 16

Mechanical stress

Answer 16

Ethylene causes triple response, ability of growing shoot to avoid obstacles-> slowing of stem enlongation, thickening of stem, horizontal growth

Question 17

Senescence

Answer 17

Programmed death of cells and organs; a burst of ethylene leads to apoptosis, programmed destruction

Question 18

Leaf abscission

Answer 18

Change in balance of auxin and ethylene control it; prices that occurs in autumn when a leaf falls

Question 19

Fruit ripening

Answer 19

Burst of ethylene production in fruit triggers ripening