18. Phytohormones - Auxin

Question 1

hormone

Answer 1

chemical messengers, coordinate cellular functions

Question 2

what is the difference between animal hormones and plant hormones?

Answer 2

animal: usually very specific hormones that come from one tissue type and act on one tissue type, many many different hormones, only certain cells can make hormones

plant: comparatively few hormones that have more numerous effects, most cells can produce them and can act on most cells

Question 3

went and thinman:

Answer 3

defined phytohormones
produced in one part and transferred to another, inducing a specific physiological response, coordinates organ activityc

Question 4

classical plant hormones

Answer 4

auxin
Gibberellins
ethylene
cytokinins
abscisic acid

Question 5

more newly discovered phytohormones

Answer 5

bassinosteroids, salicylates, strigolactones, jasmonates

Question 6

1890s: Darwin

Answer 6

goal: studies phototropism

model: covers coleoptiles with a hat

results: finds that they no longer bend towards the light

conclusion: must be some receptor in the tip that senses light and causes movement, defines phototropism

Question 7

phototropism

Answer 7

orientation of a plant in response to light

Question 8

positive phototropism

Answer 8

moving towards light

Question 9

negative phototropism

Answer 9

moving away from light

Question 10

1913: boysen-jensen

Answer 10

model: cut tip off and put other material between tip and rest of the coleoptile (agar, butter, rock, nothing), shielded bottom half

results: only the agar and control bent

conclusion: the compound that is involved in phototropism is water-soluble

Question 11

1919: paal

Answer 11

model: cut the tips off coleoptiles and put them back on asymmetrically under uniform light

results: only the asymmetric tips moved

conclusion: the signal from the tip promotes growth and the light changes its distribution, lopsided replacement of the tip causes bending even under uniform light

Question 12

1930: fritz went

Answer 12

goal: purify compound

model: concentrate auxin in agar blocks by putting cut coleoptile tips onto cubes, puts the agar block onto coleoptile stems, performs a bending assay

results: angle of curvature is proportional to amount of auxin in the block

conclusion: more cmpd = more bending

Question 13

cholodny-went theory of tropic curvature

Answer 13

asymmetric light/gravity initiates lateral relocaiton of auxin, resulting in differential growth

ie. because of uneven light, aucin concentrates and causes bending

Question 14

which side of a bent plant has more auxin?

Answer 14

shaded side

Question 15

lateral relocation of auxin causes plant cells to:

Answer 15

elongate

Question 16

auxin ___ cell elongation on shaded side

Answer 16

promotes

Question 17

1930s: H.G. van der Weij

Answer 17

model: cut the middle of the coleoptiles and puts them upside down, replaced tip with agar block

results: even with the top being an agar block and the middle cut, if it is in the right direction, auxin will move. if upside down, auxin will NOT move

conclusion: polar transport of auxin (meaning auxin only moves from cells at the top towards the bottom, bottom cells are not specialized/equipped to move auxin)

Question 18

gravitropism

Answer 18

growth response to a change in orientation relative to gravity

Question 19

shoots grow ____ center of gravity and roots grow ___ center of gravity

Answer 19

away from ; towards

Question 20

positive gravitropism

Answer 20

growing towards center of gravity, roots

Question 21

negative gravitropism

Answer 21

growth away from center of gravity, shoots

Question 22

auxin affects both:

Answer 22

gravitropism and phototropism

Question 23

what scientist was polar transport of auxin?

Answer 23

HG van der weij

Question 24

what scientist discovered phototropism/documented it?

Answer 24

darwin

Question 25

what scientist purified auxin/bending assay?

Answer 25

fritz went

Question 26

what scientist repositioned the tip/uniform light?

Answer 26

paal

Question 27

what scientist found auxin to be water-soluble/agar blocks?

Answer 27

boysen-jensen

Question 28

what is a coleoptile?

Answer 28

a young shoot tip of grass/cereal that has a hard protective sheath

Question 29

statoliths

Answer 29

starch containing plastids/amyloplasts that naturally sediment at the bottom of the cell

Question 30

how do plants detect gravity?

Answer 30

sedimentation of statoliths trigger cell membrane receptors which it interprets as the bottom/down

Question 31

statocytes

Answer 31

gravity sensing cells on root caps