Growth, yield and photosynthetic

responses to elevated CO2 in

wheat

Robert M Norton

Regional Director IPNI, ANZ

Saman Seneweera,

Sabine Posch,

Greg Rebetzke,

Glenn Fitzgerald

Australian Wheat Production

Spring Wheats – sow May, harvest December

by 2050

1-2oC warmer

50-100 mm drier

Projected climate – 2050 - A1B

Future is unclear for Australian

wheat production?

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Modeled impact of climate change on

wheat yields in the Victorian Mallee

(Grace, 2006)

CO2 * Temperature * Water

Crop growth, yield and quality are affected by all these factors

• To assess the impact of climate change on the wheat industry, need to assess the interaction of these three factors.

• Ecosystem and biotic impacts on production systems.

Adaptation strategies in response to changing climate

Effects of elevated CO2

• In C3 plants – CO2 & O2 compete for active sites on „RuBisCO‟ shift to increase gross photosynthetic C fix and reduce C loss in photorespiration.

• In both C3 and C4 plants, stomatalaperture narrows reducing water use.

• Therefore C increases & Wdecreases so TE increases.

• Increase in CO2 from 350 ppm to 550 ppm increases TE by 50%.

• This all seems simple and positive

Ainsworth & Long 2005 New Phytologist

Photosynthetic rates increased in

response to short term CO2

enrichment.

BUT when exposed to eCO2 for

extended periods, photosynthetic rates

decline. This process is known as

“acclimation”.

Various morphological, biochemical

and molecular adjustments.

Decline in plant N

RuBisCO content lower

RuBisCO activation higher

Increased Tillering

Ecosystem responses eg PNL,

pathogens)

Photosynthetic acclimation to eCO2

Seneweera et al 2005 Journal of Crop Improvement 13-31-52

2010

2100

aCO2

eCO2

Australian Grains Free Air Carbon Dioxide

Enrichment Facility (FACE)

• Located at Horsham in Western Victoria – 36oS.

• aim to answer the fundamental question of how the supply of N and

water interact with higher temperatures under elevated CO2 in

relatively low yield potential situations ie 1 to 4 t/ha

• Experimental treatments– FACE CO2 – ambient (~380 ppm) &

550 ppm

– Water – rainfed & irrigated (+50 mm)

– Sowing time – early sown (June 18) & late sown (August 22) – generates +5oC during flowering

– Nitrogen – low and supplemented –managed in response to water supply (Yitpi only)

– Cultivar - Yitpi and Janz

4 replicates

Each ring 12 m

16 m in 2009 et seq.

Spread over 5 ha site

Central CO2 Sensor,

Wind Speed &

Direction

CO2 Controller Fumigation tubes

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Seasonal Water Supply (Rain + Supplements)

Experimental Treatments – 2007, 2008, 2009

Above Ground Biomass (g/m2)

• Very few interactions among

the main treatments

– ie CO2*TOS*Water*Cultivar

• TOS and water responses

followed what would be

expected.

• CO2 increased growth at all

stages by 25-30%.

• CO2 produced more shoots per

plant.

Year Stage aCO2 eCO2

2007 Tillering 73 84

Anthesis 490 612

Maturity 656 802

2008 Tillering 167 205

Anthesis 706 917

Maturity 760 992

2009 Tillering 80 99

Anthesis 550 654

Maturity 551 730

2009 heat wave *+35oC for 2

weeks in November

Grain Yield and Yield Components

• Again,very few interactions

among the main treatments

– no CO2 response in TOS2

2008

• TOS and water responses

followed what would be

expected.

• CO2 increased yield from 2.52

t/ha to 3.22 t/ha (27%)

• In 2008, HI declined under

eCO2 with TOS2 but not in

TOS1

• CO2 increased kernel weight in

2 of 3 years but not kernel

number.

Year aCO2 eCO2

2007 Yield 258 323

SkNO 4.0 4.6

KNO 25.3 27.3

KWt(mg) 31.3 32.9

2008 Yield 247 310

SkNO 2.5 2.6

KNO 17.9 18.3

KWt(mg) 31.1 32.4

2009 Yield 252 332

SkNO 3.7 4.0

KNO 31.4 33.1

KWt(mg) 22.9 24.3

Root growth @ Anthesis(mean of both sowing times and water treatments)

Root Dry Weights to 100 cm

aCO2 = 587 ± 52 g/m2 - 12% of tops

eCO2 = 860 ± 52 g/m2 - 14% of tops

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aCO2

Effects of eCO2 on growth & N demand

(2008 data)

Factor

[CO2]

(mol/

mol) GS30 GS65 GS90

Plant N (%) 550 3.69 1.90 1.56

-5% 380 3.77 2.05 1.63

N Uptake (g/m2) 550 7.47 17.24 15.73

+23% 380 6.11 14.28 12.73

Kernel N% 550 3.04

-3% 380 3.15

Similar response in all 3

years

Evidence of acclimation

Decline in grain protein

content of ~1% in each

experiment

Changes in quality and

mineral content (on-going

study).

Yitpi & Janz did not show

significantly different

responses to eCO2

Modeling of Impacts - Upscaling

No Adaptation

Adaptation - Cultivar Differences

• Literature

– Indeterminate types more

responsive (soy, wheat)

– N fixing more responsive

– Vigerous more responsive

– NR‟ase implicated in acclimation

• Ziska compared an “old” &

“new” culitvar in OTC‟s

• Concluded that

responsiveness to eCO2 is

related to “indeterminacy” ie

the ability to set added

heads/seed sites.Marquis – released 1908 (clear bars)

Oxen – released 1996 (gray bars)

At two plant densities (low/high),

Cultivar Effects

• Yitpi v Janz

– Very little difference in response to eCO2

– Some canopy differences early, but otherwise nothing

• 2008/2009

– Glasshouse reponses of a range of cultivars –Tillering & Photosynthetic responses

• 2009 - look at a wider set of cultivars – traits

– Widely Adapted (Kauz Dwarf = Zebu); TE differences (Hartog, Drysdale) High grain number (Silverstar); Low Tillering (H45); Current best adapted (AGT Gladius)

Shoot Numbers under eCO2

No significant interaction between shoot number and eCO2

But – the change in shoot number was most for mid-tillering

types.

Growth response of 8 cultivars to eCO2

• In the FACE experiment – biomass at maturity

• Significant interaction between CO2 and cultivar

• Zebu was most responsive to eCO2 +59%. Hartog least

responsive +11%

Bio

mass M

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g/m

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aCO2

eCO2

SE = 59

Yield response of 8 cultivars to eCO2

• In the FACE experiment – compromised by heat wave

during grain filling.

• No interaction between cultivar and CO2

• BUT – some cultivars (eg Gladius, Zebu) appeared to

have a larger response than others (eg Hartog, H45,

Silverstar)

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Kernel weight

• Significant interaction among the cultivars for kernel weights –

interaction was for CO2*Irr*Cultivar

• Silverstar (high “sink”) did increase kernel weight with eCO2

under rainfed, but not under irrigation. H45 (low “sink”) did not.

• Reflect a variation in the degree of sink limitation?

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Summary• Increase in biomass and grain yield ~ 25% with CO2 @

550 ppm.

• Less response with hotter conditions (later sowing).

• No particular yield component stands out – they are

indicators of the path not the destination.

• Grain protein contents were lower under eCO2.

• Little evidence of differences between Janz and Yitpi –

these types are still sink – not source – limited.

• Some evidence of differential response among cultivars

– maybe high growth rates, low determinacy, (high

NUE?).

• Seek future types that are less sink limited and with

lower acclimation response.

FACE LinkagesCore Agronomy

(wheat/pulse):

CO2*Water*Temp

(Norton & Fitzgerald)

Pathology(Luck)

Physiology(Seneweera)

Belowground

(Soil Types)(Armstrong)

Modelling(O’Leary)

Morphology

(Rebetzke)Photosynthetic Effects

(Leaky/Ainsworth)

(Makino) (CAAS Han)

N Dynamics

(Cammarano/

Fitzgerald)

Insect

populations

(Yen)

BYDV, Crown Rot, Net Blotch

(Trebicki/Freeman/Powell)

Short term C/N

dynamics (Lam)

Stripe Rust

(Hollaway/Chakraborty)

Validation/Prediction

(O’Leary, APSRU,

CSIRO)

Modelling

(Griffiths)

CAAS Changping

CAS Wuxi

BNL

NZ Pasture FACE

SoyFACE (Illinois)

RiceFACE (Japan)

Data Sharing & Access

(O’Leary, Fitzgerald)

Soil Processes incl.

GHG (Chen/Li)

Grain Quality

(Panozzo)

Brassica(Tomkins)

Informatics, Biometrics

(Partington)

System performance

Design specifications

(Mollah)

Remote Sensing,

Database

(Fitzgerald)

Agronomy

(Norton)

Horsham & Walpeup Yield, Agronomy -

wheat (Norton)

Microbial

functions

(Mele)

Pests & Diseases

(Jo Luck)

Crown Rot

(Trebicki)

N/C

dynamics

(Arndt)

C dynamics/

sequest.

(Mathers/

Robertson)

New var. & pulses

(Norton, Brand)

Acknowledgements

Grains Research & Development Corp.

Department of Agriculture, Fisheries and Forestry

Victorian Dept. Primary Industries

Australian Dept. Ag, Fisheries & Forestry

Australian Dept. Climate Change

The University of Melbourne

IPNI and the IPNI Global Wheat Group for

support to attend this conference.

http://www.ipni.net