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Flashcards in Auxin Deck (35):
1

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

tip

2

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

bending

3

chemical identity of auxin

indole-3-acetic acid (IAA)

4

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

0.5 nm

5

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

shoots

6

primary synthesis sites

shoot apical meristems and young leaves

7

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

gene expression

8

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

axial

9

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

shoot tip to root tip

10

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

diffuses

11

polar transport requires

metabolic energy

12

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

phloem translocation

13

major site of polar transport is the --

vascular parenchyma tissues

14

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

chemiosmotic model

15

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

secondary active transport

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+)

efflux

17

important components of the auxin efflux carrier complex

PIN proteins

18

auxin promote growth in stems and coleoptiles while inhibiting

root growth

19

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

10-12 minures

20

full response requires -- and above optimum concentration auxin becomes inhibitory

sucrose

21

auxin stimulates growth by increasing the -- of the cell wall

extensibility

22

m

wall extensibility

23

Y

yield threshold

24

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

expansins

25

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

phototropism

26

coleoptile stimulated by light will transport IAA --

laterally

27

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

basipetally

28

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

curvature toward light

29

gravitropism also involves -- redistribution of auxin

lateral

30

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

small auxin up-regulated RNAs (SAURs)

31

dense plastids detect gravity

amyloplasts = statoliths

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

ER

33

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

starch sheath

34

-- cells causes redistribution of auxin

gravity sensing

35

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

lower