Plant growth responses to soil physical constraints.
Scottish Crop
Research Institute
Valentine T.A., Karley A.J., Binnie K., Post J., Young M., Wright G., Marshall B., Hallett P.D., McKenzie B.M., Bengough A.G.
Environment Plant Interactions, Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA
[email protected]
Background
Root growth can be constrained by soil physical properties such as soil strength. This can lead to smaller variable yield and
decreased water and nutrient uptake. Plants respond to these constraints by changes in overall root structure and responses at
the individual meristem level such as increasing border cell production. We are studying a range of traits within a selection of
barley cultivars, to investigate how different rooting types overcome these constraints.
Soil physical properties
(A) Soil strength (penetrometer resistance)
increases as soil dries, and is greatest in
compacted soil.
A
B
C
30
6
Penetration Resistance, MPa
5
4
Thin sections of ploughed soil: Pore space appears
black (B; using polariser & analyser) or white (C;
light field). Thus visible porosity and its distribution
can be quantified (D). This is however only a
fraction of overall porosity
3
2
Compacted
Deep Plough
Minimum Tillage
Zero Tillage
Plough
1
0
10
25
50
D
25
Visible porosity (%)
Soil strength depends
on soil type, water
content and soil
structure (A). Soil
structure can be
influenced by different
tillage treatments (B-D)
200
20
Full
15
X10 mag
10
5
0
Compact
Deep
Plough
Min till
No till
Plough
Treatment
Water Potential, kPa
Early seedling properties
60
50
40
8
30
6
4
20
2
10
0
0
600
500
400
300
200
100
140
Root:Shoot
Branching
Angle
0.10
80
0.08
60
0.06
0.04
40
0.02
20
0.00
0
Fanfare
Pastoral
Pipkin
0
Border cell numbers have also been
assessed in a range of cultivars (C)
2
Bo 1/5
w
m
a
C n
h
D ime
er
ka
Fa d o
H n fa
ar
un re
o~
ijo
H
S9
2
Li
M na
eh
ol
a
M
or
ex
O
Pa ptic
st
or
a
Pi l
pk
in
Su
m
o
100
2/
120
/1
0.12
Dual thin gel layer plates (A) are being
used to assess seedling root depth
and inital root angle (B).
o
Root:Shoot Ratio
0.16
C
700
Border cell number
B
10
0.14
800
70
Depth
Length
B8
3
12
Root Length, mm
14
Branching Angle,
Root Depth, mm
16
A
Culitvar
Sumo
Mature plant above and below ground traits
Cultivar and mutant barley lines
have been assessed for developmental traits, e.g time to tillering,
number of tillers and distribution
of fresh weight across above and
below ground portions of the
plants.
B
A
0.3
C
0.2
Bowman
A - Greenhouse set up for
barley
B - Example above ground
barley portion and seed head
at harvest.
C - Principle components
Graph show relative expression of BPW
analysis
of fresh
weight
(involved
in water
uptake) and GAPDH, in
distribution
between
roots of plants
grownbarley
in soil at a range of
water and
availabilities
cultivars
mutants (Main
tiller, remaining tillers,
leaves, seed heads, total
root)
D - Root harvesting from
specific depths
E - Variation in rooting depth
between cultivars. Cumulative fresh weight of root
E
material (from top through to
100cm depth).
0
PCO2 (16.16%)
B83
-0.5
Westminister
Bowman - mutant 2
Bowman - mutant 6
0.1
Bowman - mutant 1
Bowman - mutant 3
Kenia
Golden promise
Optic- root mutant 2
Optic - root mutant 3
Troon
Bowman - mutant 5
0
-0.1
0
0.5
1
Optic - root mutant 1
Derkado
-0.2
-0.3
-0.4
20
Cumulative depth
40
60
Troon
80
100
Bowman - mutant 4
-0.5
B83
1
Derkado
3
4
PCO1 (71.97%)
Westminister
Optic
Optic - root mutant 1
Optic - root mutant 2
Optic - root mutant 3
6
Bowman
7
Bowman - mutant 1
Bowman - mutant 2
8
Bowman - mutant 3
9
Bowman - mutant 4
Bowman - mutant 5
Bowman - mutant 6
Acknowledgements
Future work
5
4.5
Relative mRNA level (BPW / GAPDH)
Plants with specific root traits and combinations of traits
will be used to assess their relative importance on the
plants’ ability to overcome physical constraints.
Plants will be assessed under differerent soil types,
compaction levels and water availability.
Expression of genes linked to responses of plants to
soil conditions will be explored.
Golden promise
5
10
-0.6
Kenia
0
2
Cumulative fresh root mass (g)
Optic
D
4
3.5
3
2.5
2
1.5
1
0.5
0
5
50
Soil water tension
500
mRNA levels of
BPW obtained by
quantitative RT-PCR
in plant roots grown
under different water
availability, in soil
cores. BPW is
involved in water
uptake
This work is supported by Scottish Executive
Environment and Rural Affairs Department.
Barley cultivars and mutants were obtained from
collections of Barley maintained by Genomics
Programme SCRI. - See also reference Caldwell,
D., McCallum, N., Shaw, P., Muehlbauer, G.J. &
Waugh, R. (2004) A structured mutant population
for forward and reverse genetics in barley
(Hordeium vulgare L.). Plant Journal 40, 143-150.