Root traits governed by biological and environmental...
Transcript of Root traits governed by biological and environmental...
Breeding for root traits: a new frontier
Critical functions
Functional traits still poorly understood
Dynamic
High C costsDon Tremain, Tree with rootsGetty Collection
Talk outline Plant strategies belowground: root trait
evolution
Effects of plant management and environment on root dynamics & functioning
(UC Davis walnut research & breeding program)
(USDA corn & sunflower water deficit research )
Root system structure
1st order
2nd
(3rd)
Coarse roots (structural support, plumbing)
Fine roots (physiologically active, ephemeral)
Evolved plant strategies below ground
What can we learn from natural selection?
Mature tree traits
SRL
(m g
-1)
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
QAQR
AS
AN
FG
BL
CG
CO
PV
PS
Fast Slow
SR
L (m
g-1
)
0
50
100
150
200
250
300 (a)
SRLFast > Slow
(P<0.05)
Seedling traits
• faster root proliferation• more soil explored
Root morphology
Comas et al. 2002; Comas & Eissenstat 2004
PV0.00
Aceraceae Fagaceae PinaceaeAN AS TCQR QA
Fast-growing seedlings
Fast Slow
Consistency Index = 0.44
= m g-1SRL
- Unordered linear parsimony- Square-root reconstruction- Tree based on APGII 2003
Comas & Eissenstat 2009
Comas et al 2012 IJPSCenozoicPaleo-geneCretaceousTriassicPermianCarboniferous
Paleozoic Mesozoic
Jurassic Neo-gene
Cenozoic
300 200 100 0 MY
0.13-0.400.40-0.680.68-0.960.96-1.241.24-1.511.51-1.791.79-2.072.07-2.352.35-2.622.62-2.902.90-3.18
Phylogenetic pattern
Distance from each node to root of the tree (MY)
0 100 200 300 400
Diam
eter (m
m)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4Paleozoic Mesozoic Cen.
Comas et al 2012 IJPS
Evolution in root diameter
R2 = 0.83P < 0.05
Lower [CO2]Greater stom. densityHigh leaf vein density
Thinner roots = less cortex for less impedance to water movement?
Roo
t len
gth
dens
ity
(cm
/cm
3 )
6
4
2
20 40 60 80 100 SRL (m/g)
Comas et al 2012 IJPS, data from Withington et al 2006
Trade-offs between morphology & RLD
R2 = 0.69P < 0.05
Conclusions• Within close relatives, longer SRL and thinner
roots allow fast-growing species to exploit soil pockets more quickly (with higher costs but faster returns on these costs)
• Root morphology more ‘hard-wired’ than physiology
• Evidence suggests that angiosperms evolved thinner roots with longer SRL, potentially to increase water uptake & transport, and out compete plants in upland habitats
NE US vineyards• Juice grape production
• Lake Erie region, NY
• Soil: Chenango gravelly loam
• Training: high-wire bilateral cordon
• Minimal pruning to reducecosts and raise crop yield
• Issues with alternate-bearing vines
Vitis labruscana Bailey cv Concord
Effects of plant management and environment on root dynamics & functioni
Balanced growth theory - does irrigation compensate for root growth?
Irrigated vs non-irrigated?
Competing sinks - do roots compete with fruit for plant carbon?
Minimal vs heavy pruning? Timing?
Questions
• Roots compete with fruit for plant carbon
• Root growth is bimodal - major root flush in spring with a smaller root flush in fall
Conventional wisdom in grape
Mullins MG, Bouquet A. Williams LE. 1992. Biology of the Grapevine.
• 25-yr-old vines, treatments initiated in 1991
• Completely randomized block design; 2x2 factorial
• experimental unit = 5 vines plus 2 as buffer
• study duration = 4 years (1997-2000)
• roots observed with minirhizotrons
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Block 4Block 1
Block 3Block 2
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xexperimental vinesbuffer vinesroot tubes
Experimental layout
Root production
Ave
rage
tota
l roo
t pro
duct
ion
(mm
cm
-2 y
r-1)
0.0
0.5
1.0
1.5
2.0
2.5
NI Irr NI Irr
Dry years Wet years
Comas et al. 2005 New Phytologist
Root distribution in dry years
1997
1998
Dep
th (c
m)
1999
2000
Mean fine root production (%)0.0 0.2 0.4 0.6 0.8 1.0
0 - 20
21 - 40
41 - 60
61 - 80
81 - 110
*
**
**
0 - 20
21 - 40
41 - 60
61 - 80
81 - 110
0 - 20
21 - 40
41 - 60
61 - 80
81 - 110
0 - 20
21 - 40
41 - 60
61 - 80
81 - 110
Non-irrigatedIrrigated
(wet)
(dry)
(dry)
(wet)
Comas et al. 2005 New Phytologist
Timing of root production
1997
0.00
0.02
0.04
0.06 Heav/NIHeav/IrrMin/NIMin/Irr
1998
New
root
s (m
m c
m-2
)
0.00
0.02
0.04
0.06
1999
0.00
0.02
0.04
0.06
2000
Mar Apr May Jun Jul Aug Sep Oct Nov
0.00
0.02
0.04
0.06
Comas et al. 2010 AJGWR
(wet)
(dry)
(dry)
(wet)
Root production rate
Comas et al. 2005 New Phytologist
0.00
0.01
0.02
0.03
Vine phenology
Bud dev Flwr dev Frt dev Frt ripe Sht dormBud dev Flwr dev Frt dev Frt ripe Sht dorm
Rat
e of
root
pro
duct
ion
(mm
cm
-2 d
-1)
0.00
0.01
0.02
0.03
0.00
0.01
0.02
0.0319971998
1999 2000
Wet yearsDry years
Heav/NIHeav/IrrMin/NIMin/Irr
Ear dev Frt set Frt dev Frt ripe Sht dorm Ear dev Frt set Frt dev Frt ripe Sht dorm
v
vbl
bl
v
bl
vbl
(cm)
Mea
n fin
e ro
ot p
rodu
ctio
n (m
m c
m-2
d-1
)
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
Apr May Jun Jul Aug Sep Oct0.0
0.5
1.0
1.5
0 - 20
21 - 40
41 - 60
61 - 80
Apr May Jun Jul Aug Sep Oct
81 - 110
Root phenology & distribution
Comas et al. 2005 New Phytologist
Minimally pruned Heavily prunedDepth
Conclusions
• No evidence of C limitations on root growth
• Amount & timing of root growth is controlled by both plant and environment (canopy development & soil moisture)
Whi
te ro
ots
(%)
0255075
100
% white % dark Plot 1 Zero
Root age (weeks)0 1 2 3 4 5 6 7 8 9
TTC
redu
ctio
n (A
g-1
DW
)
0
10
20
30
40
50
60
70
80
0
5
10
15
20
25
30
35
40
45
50
55
RespirationTTC reduction
Respiration (nm
ol O2 g -1 D
W s -1)
(a)
(b)
Comas et al. 2000 New Phytologist
Root metabolism with age
0
20
40
60
80
100
120
140
White Brow n Black Control
TTC
redu
ctio
n (A
g-1
d.w
t.)
Root pigmentation
3902408 Jul 97 30 Mar 981 Nov 97
White Brown Black
Metabolic decline w/ pigmentation
1 mm
Comas et al. 2000 New Phytologist
• Other work has shown nutrient uptake capacity declines quickly with root age (P in apple, Bouma et al 2001; N in grape, Volder et al 2005); What about water uptake?
• Young roots have high C costs but greatest nutrient acquisition capacity
• Apples vs oranges (Eissenstat 1999)
• Other environmental factors, especially temperature effects on root growth & function?
Root functioning with age
• Some broad generalizations may hold (fast growth, drought adapted = long SRL, thin diameters)
• Complexity in root functioning demands in-depth knowledge of the system breeders are breeding for
• What root traits do plants need to sustain yields under different types of drought? Different strategies for different species?
Implications & future directions
Acknowledgements
Root evolutionKevin Mueller, Univ MinnesotaLyla Taylor, Univ of SheffieldPeter Midford, NESCentHilary Callahan, Barnard/ColumbiaDavid Beerling, Univ of Sheffield
Grape ResearchDavid Eissenstat, PSUAlan Lakso, Cornell Laurie Anderson, Ohio WesleyanRick Dunst, Cornell Vineyard Lab
Funding sourcesUSDA/CSREES Eastern & Western Viticulture ConsortiumNSF IOSNESCent
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
bloomveraison
harvest
bloom
veraisonharvest
bloom
veraison
harvest
bloom
veraison
harvest
1997
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1998
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1999
Roo
ts p
rese
nt (
mm
cm
-2)
0.00.20.40.60.81.01.21.41.6
2000
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
0.00.20.40.60.81.01.21.41.6
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
B. Brown rootsA. White roots C. Total roots
Heav/NIHeav/Irr
Min/NIMin/Irr
(wet)
(dry)
(dry)
(wet)
Standing root populations veraison
veraison
veraison
veraison
Comas et al. 2005 New Phytologist