Auxin

Question 1

Darwins concluded that there was a signal that was produced in the – and moved to the growth zone

Answer 1

tip

Question 2

Went showed that a chemical could be collected from the coleoptiles which cause – in the absence of light

Answer 2

bending

Question 3

chemical identity of auxin

Answer 3

indole-3-acetic acid (IAA)

Question 4

molecular distance of – between a fractional positive charge on the aromatic ring and a negatively charged carboxyl group

Answer 4

0.5 nm

Question 5

IAA biosynthesis is associated with rapidly dividing and growing tissues, especially –

Answer 5

shoots

Question 6

primary synthesis sites

Answer 6

shoot apical meristems and young leaves

Question 7

IAA is transported into the cytosol and nucleus where it binds to a receptor and the complex regulates –

Answer 7

gene expression

Question 8

roots and shoots show – polarity which is independent of orientation with respect to gravity

Answer 8

axial

Question 9

polar transport is the principal cause of an auxin gradient extending from

Answer 9

shoot tip to root tip

Question 10

polar transport proceeds from cell to cell: exits through plasma membrane – across cell wall and enters next cell through plasma membrane

Answer 10

diffuses

Question 11

polar transport requires

Answer 11

metabolic energy

Question 12

velocity of polar transport is faster than diffusion but slower than –

Answer 12

phloem translocation

Question 13

major site of polar transport is the –

Answer 13

vascular parenchyma tissues

Question 14

polar transport depends on proton pumping out of the cell and into the cell wall

Answer 14

chemiosmotic model

Question 15

IAAH diffuses into the cell or IAA- is pumped into the cell by – via an H+ IAA- symporter

Answer 15

secondary active transport

Question 16

once IAA- enters the cytosol, it accumulates and then – occurs via special transporters driven by the negative membrane potential (relative to the cell wall, which has accumulated H+)

Answer 16

efflux

Question 17

important components of the auxin efflux carrier complex

Answer 17

PIN proteins

Question 18

auxin promote growth in stems and coleoptiles while inhibiting

Answer 18

root growth

Question 19

for excised tissues, addition of auxin stimulates growth after a lag period of about

Answer 19

10-12 minures

Question 20

full response requires – and above optimum concentration auxin becomes inhibitory

Answer 20

sucrose

Question 21

auxin stimulates growth by increasing the – of the cell wall

Answer 21

extensibility

Question 22

m

Answer 22

wall extensibility

Question 23

Y

Answer 23

yield threshold

Question 24

proteins in cell walls that loosen cell walls under acidic pH by weakening the hydrogen bonds between polysaccharides in the wall

Answer 24

expansins

Question 25

growth toward light and is expressed in all shoot and some roots

Answer 25

phototropism

Question 26

coleoptile stimulated by light will transport IAA –

Answer 26

laterally

Question 27

once IAA reaches shaded side it is transported – to the elongation zone, stimulating cell elongation (by acidifying the cell wall)

Answer 27

basipetally

Question 28

acceleration of growth on the shaded side and slowing of growth on the illuminated side causes –

Answer 28

curvature toward light

Question 29

gravitropism also involves – redistribution of auxin

Answer 29

lateral

Question 30

gravitropism causes a rapid differentiation in the expression of auxin-stimulated mRNA –

Answer 30

small auxin up-regulated RNAs (SAURs)

Question 31

dense plastids detect gravity

Answer 31

amyloplasts = statoliths

Question 32

statoliths fall through the cytoplasm and trigger the stimulus by either interacting with the cytoskeleton or by exerting pressure on the – at the bottom of the cell

Answer 32

ER

Question 33

stimulus is triggered occurs in shoot’s – which is a layer of cells that surrounds the vascular tissue or in root cap

Answer 33

starch sheath

Question 34

– cells causes redistribution of auxin

Answer 34

gravity sensing

Question 35

– concentrations of auxin in the upper side of a horizontal root causes more rapid growth and bending downward

Answer 35

lower