Effects of high peaks vs high background ozone on wheat

Felicity Hayes, Stephanie Osborne, Katrina Sharps, Harry Harmens, Gina Mills

CAPER 4th-6th April 2016

Introduction

Comparing response to ozone supplied as peaks (local/regional pollution) and background (hemispheric pollution)

2 current varieties of wheat (breadmaking). Mulika (released 2011) and Skyfall (released 2014)

Methodology

Wheat seeds planted in loam-based compost mix, 25 litre containers Exposed to ozone in solardomes 15th May – 12th August 2015

Measurements made included: Harvest index Number of ears Grain number per ear and 1000 grain weight C and N content of grains and soil (in progress) ACi curves of flag leaves Chlorophyll content of flag leaves Asat of flag leaves Stomatal conductance

Drought experiment - Steph

High peaks vs high background treatments

O3 (24h mean) background peaks

Low 27.0 30.3

Medium 37.0 39.2

High 48.6 50.2

Very high 56.5 55.4

0

20

40

60

80

100

120

Friday Saturday Sunday Monday Tuesday Wednesday Thursday

Ozo

ne

, pp

b

0

20

40

60

80

100

120

Friday Saturday Sunday Monday Tuesday Wednesday Thursday

Ozo

ne

, pp

b

8 ozone treatments applied in matching pairs with “same” seasonal mean but applied as peaks or background

Season mean profiles

Results

Mulika

19th June 2015

Low peaks Very High peaks

A little senescence high in the canopy

A lot of senescence low in the canopy

Canopy height was the same

Results

Skyfall

19th June 2015

Low peaks Very High peaks

Some senescence high in the canopy

A lot of senescence low in the canopy

Canopy height was the same

0

10

20

30

40

50

60

70

80

15-Jun 25-Jun 05-Jul 15-Jul 25-Jul 04-Aug

Chlorophyll index Mulika

Background

Peaks

0

10

20

30

40

50

60

70

80

15-Jun 25-Jun 05-Jul 15-Jul 25-Jul 04-Aug

Chlorophyll index Skyfall

Background

Peaks

Accelerated senescence shown in chlorophyll index data

For Mulika the decline in chlorophyll content was similar in the high background and high peaks ozone treatments

For Skyfall the decline in chlorophyll content was faster with high peaks

anthesis anthesis

Accelerated senescence shown in canopy NDVI data

Continuously logging NDVI sensors detected small differences in canopy greenness

Differences are not as pronounced as single leaf chlorophyll measurements

Ears and stems are also included in the measurement

0.000

0.200

0.400

0.600

0.800

1.000

Re

lati

ve N

DV

I

Mulika

medium background low background

0.000

0.200

0.400

0.600

0.800

1.000

Re

lati

ve N

DV

I

Skyfall

medium background low background

anthesis anthesis

Growth stageGrowth stage (27/7/2015)

Skyfall

There was no evidence that development of Skyfall was accelerated by ozone. (growth stage the same across all treatments).

A hint that development might have been accelerated very slightly in Mulika.

(development of Mulika was faster than for Skyfall).

86

87

88

89

90

91

92

Low Medium High V high

Gro

wth

sta

ge

background peaks

Mulika

83

84

85

86

87

88

Low Medium High V high

Gro

wth

sta

ge

background peaks

Asat (Skyfall)

0

10

20

30

40

Low Medium High Very high

Asat (23/24 June 2015)

Background Peaks

0

10

20

30

40

Low Medium High Very high

Asat (14 July 2015)

Background Peaks

Asat was similar across all ozone treatments before anthesis. There was a decrease in Asat with increasing ozone after

anthesis The decline was much faster with the ‘peaks’ treatments.

Anthesis 1st July

Asat related to chlorophyll content

R² = 0.69

0

5

10

15

20

25

30

35

40

0 10 20 30 40 50 60 70 80 90

Asa

t (

um

ol m

-2 s

-1)

SPAD

June & July 2015 (polynomial function)

R² = 0.67

0

5

10

15

20

25

30

35

40

0 200 400 600 800 1000

Asa

t (

um

ol m

-2 s

-1)

Gs (mmol m-2 s-1)

June & July 2015 (polynomial function - high Gs)

Asat was related to chlorophyll content. On individual days the relationship between Asat and Gs was

good, and still fairly good when all data was combined.

Yield related to chlorophyll (cumulative photosynthesis)

r² = 0.91

0

2

4

6

8

10

12

0 10 20 30 40

Yie

ld, t

on

ne

s/h

ect

are

Cumulative chlorophyll / Asat / NDVI

background

peaks

r² = 0.60

0

2

4

6

8

10

12

0 10 20 30 40

Yie

ld, t

on

ne

s/h

ect

are

Cumulative chlorophyll / Asat / NDVI

r² = 0.85

0

10

20

30

40

50

60

0 10 20 30 40

10

00

gra

in w

eig

ht

Cumulative chlorophyll / Asat / NDVI

r² = 0.91

0

10

20

30

40

50

60

0 10 20 30 40

10

00

gra

in w

eig

ht

(g)

Cumulative chlorophyll / Asat/ NDVI)

Background

Peaks

Mulika Skyfall

From anthesis to harvest

Wheat: Provisional flux-effect relationships using the standard

wheat model, SWP not included but plants kept well-watered

y = -282.52x + 9339.1R² = 0.2048, p = 0.17

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

0 2 4 6 8 10

Ave

rage

yie

ld (

kg/h

a)

POD6 (generic)

Mulika

All

Peak

Background

Linear (All) y = -755.02x + 11644R² = 0.74, p<0.001

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

0 2 4 6 8 10

Ave

rage

yie

ld (

kg/h

a)

POD6 (generic)

Skyfall

Peak

Background

R² = 0.7519

y = -0.3x + 6.3928R² = 0.62, p<0.001

2

2.5

3

3.5

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4.5

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5.5

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0 2 4 6 8 10

Hu

nd

red

gra

in w

eigh

t (g

)

POD6 (generic)

Skyfall

Background

peak

all

Poly. (peak)

Linear (all)

Yiel

d1

00

gra

in w

eigh

t

y = -0.1805x + 5.6049R² = 0.7545, p<0.001

2

2.5

3

3.5

4

4.5

5

5.5

0 2 4 6 8 10

Hu

nd

red

gra

in w

eigh

t (g

)

POD6 (generic)

Mulika

Background

Peak

all

Linear (all)

No significant effects of O3 profile

Mulika Skyfall

MM POD3IAM function, with new data added

y = 0.98 - 0.0064*POD3IAMr² = 0.62, p < 0.0001

0.0

0.2

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0.6

0.8

1.0

1.2

0 10 20 30 40 50

Re

lative

yie

ld

POD3IAM (mmol m-2)

MM data

Mulika

Skyfall

Linear (MM data)

Linear (Mulika)

Linear (Skyfall)

For integrated assessment modelling across Europe

Summary

Senescence was accelerated by ozone. In Mulika the rate of senescence was the same when ozone was applied as either higher peaks or higher background.

There was no evidence that the rate of development was affected. After anthesis, Asat was decreased with increasing ozone treatment and

this was related to the changes in senescence (chlorophyll content). For Skyfall, the decline was faster in the ‘peaks’ treatments.

Yield and 100 grain weight were both decreased with increasing ozone. The apparent differences between ‘peaks’ and ‘background’ responses were explained by ozone flux (ozone fluxes were higher in the ‘peaks’ treatments as ozone was present in conditions favourable to uptake).

This study provides evidence that the flux based dose-relationships developed using experiments with episodic ozone exposure are also applicable for predictions of yield responses with increasing background ozone concentrations.