Dennis Timlin1 - Soo-Hyung Kim2 - Kofikuma Dzotsi3 - Matthijs Tollenaar4 - Saratha Kumudin4 - Haishun Yang5 - Gustavo Maddonni6 -Jon Lizaso7- David Fleisher1 - François Tardieu8 - Armen Kemanian9 - Bruno Quebedeaux10 - Kenneth Boote3 - Claudio Stockle11 1USDA-ARS, Beltsville, MD , 2University of Washington, Seattle, WA, 3Univ. of Florida, Gainesville, FL, 4Monsanto Corporation, Research Triangle Park, NC, 5Univ. of Nebraska, Lincoln, NE, 6Cátedra de Cerealicultura Fac. Agronomía. UBA, 7Fitotecnia, Technical Univ. Madrid, Spain, 8INRA, Montpellier, France, 9Penn State Univ. State College, PA, 10Univ. of Maryland, College Park, MD, 11Washington State Univ., Pullman, WA

Crop models are being used as tools to assess climate change impacts primarily through temperature and water stress effects

It is therefore important to accurately estimate leaf area expansion and senescence, and their linkage to leaf ontogeny and phenology particularly when average temperatures are above the optimum.

Investigate and assess different approaches to modeling leaf expansion in maize.

Investigate the effects of plant population on leaf expansion.

Three models were used:

▪ Hybrid Maize (Haishun Yang, Univ of Nebraska)

▪ AgMaize, (Kofikuma Dzotsi, Jon Lizaso, Thijs Tollenaar, and Saratha Kumudini, AgMIP)

▪ MaizSim, (Soo-Hyung Kim, Dennis Timlin, and David Fleisher, Univ. of Washington and USDA-ARS)

Relationship between maximum area of the leaf and node position (Stewart and Dwyer, 1994)

Area of any one leaf is proportional to area of largest leaf The proportionality factor is a function of leaf node position

Relationship between leaf longevity and node position (Lizaso et al., 2003)

There are commonalities to the simulation methods. These include:

Leaf area expansion can be based on the rank of the leaf and relative placement on the stem.

Potential growth rate and longevity are modeled as a function of temperature.

Leaf sizes can be modeled relative to the size of the largest leaf.

CO2 is fixed. Overall, LAI simulation is based on a combined

scheme of CERES-Maize, typical Wageningen models (e.g., WOFOST), and APSIM: Individual leaf growth is simulated. Leaf area calculated on

a plant basis as it is incremented area and increased by the number of leaf tips appearing on a given day.

Temperature determines daily potential leaf area expansion, parameters depend on growth stage.

Photosynthate availability and water stress regulate final daily LAI increase (or senescence after silking).

Leaf addition is by GDD (linear).

Other settings: Location: Mead, Nebraska Year: 2012 Planting: May 1 Maturity: RM 105d Water: fully irrigated

Pop=80k/ha

Pop=60k/ha

0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25 30 35 40 45

Ra

te o

f le

af

ap

pe

ara

nce

(le

ave

s/d

ay

)

Average air temperature (degree C)

TCeil

LTAR

bopt

R

TTnPhyllochro

max_

Topt

Tb=8

Rmax_LTAR

optceil

opt

TT

T

optoptceil

ceil

T

T

TT

TT

Tb= 0 OC Topt = 31 OC Tceil = 44 OC

(a) Leaf initiation

Mean ambient temperature (C)

10 20 30 40

Prim

ord

ia d

-1

0.0

0.2

0.4

0.6

0.8

1.0

1.2Warrington & Kanemasu

(1983b)

Line fit using data from SPAR chambers

(b) Leaf appearance

Mean ambient temperature (C)

10 20 30 40

Lea

ve

s d

-1

0.0

0.1

0.2

0.3

0.4

0.5

0.6Tips

Ligules

LeavesInitiated += beta_fn(T_cur, Rmax_LIR, T_opt, T_ceil);

0

5

10

15

20

25

0 5 10 15 20 25

Le

af

tip

s o

r le

af

lig

ule

s

TLU

Leaf ligules

Leaf tips

Duration of leaf-area expansion

For each individual leaf, the time of leaf tip (A) and collar (B) appearances expressed in thermal leaf unit are calculated.

Individual leaf expansion occurs linearly between these two points A and B.

Leaf longevity is calculated to determine when senescence should start (point C).

Senescence occurs between points C and D.

Maximum area of a leaf is a function of its rank and area of largest leaf.

Daily mean temperatures are used.

y = -0.0019x2 + 0.0967x - 0.2818 R² = 0.8563

y = -0.0041x2 + 0.1977x - 1.4631 R² = 0.8804

y = -0.0051x2 + 0.2249x - 1.5504 R² = 0.8591

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35

No

rma

lize

d le

af

are

a

Mean temperature (oC)

4 leaf stage

8 leaf stage

12 leaf stage

Individual leaf growth and senescence are calculated

Maximum potential size is a fraction of the largest leaf dependent on the leaf rank.

Leaf addition and leaf appearance have separate parameters.

Leaf expansion, addition and appearance calculated using hourly temperature, rates determined using a beta function.

Based on Lizaso et al. (2003) and Fournier and Andrieu (1998) but does not use directly use GDD

Leaf expansion parameters are adjusted by hourly growth temperature.

Lizaso et al., 2003

)(

12

Tfe

ekeA

dt

dA

ii

ii

tetke

tetke

ieii

)(

12

Tfe

ekeA

dt

dA

ii

ii

tetke

tetke

ieii

ke is an intrinsic growth rate that depends on leaf number te is leaf longevity and depends on leaf number Aei is the final optimum area of the leaf at rank i

pk

b

pk

b

T

TT

T

TTTf 0.1exp,0.0max)(

(A)

Temperature (oC)

10 15 20 25 30 35

Re

lative

fin

al le

af a

rea

0.0

0.2

0.4

0.6

0.8

1.0

1.2

(B)

Temperature (oC)

10 15 20 25 30 35

Rela

tive

te

0.5

1.0

1.5

2.0

2.5

Re

lative

ke

0.2

0.4

0.6

0.8

1.0

1.2

Whole canopy (Kim et al., 2007; Bos et al., 2000; Tollenaar, 1989) and individual leaves (Hesketh and Warrington, 1989; Fournier and Andrieu, 1998);

Ke (◦) is slope of the leaf growth rate

te (●)is the number of GDD (base 8) for a leaf to reach 50% of its final size (both parameters are from Jon Lizaso’s paper). Data are from Beltsville SPAR experiments

Five site years of Maize harvests from the Eastern Shore of Maryland, Wye, MD – 2006 2007 and 2008

Georgetown Delaware – 2006 and 2007, irrigated Weekly to bi-weekly destructive harvests and

measurement of plant phenology, leaf area Average growing season temperatures range

from 19 to 23C Minor to no water stress during leaf

expansion

Beltsville

Wye

Georgetown

Hybrid Maize

No calibration was performed

AgMaize

Leaf senescense rate, and maximum area and node position of largest leaf calibrated.

MaizSim

Maximum juvenile leaf number.

MD, 2006

0 20 40 60 80 100 120

2000

4000

6000

8000

10000MD, 2007

0 20 40 60 80 100 120

Leaf surf

ace a

rea, cm

2 p

lant-1

MD, 2008

Days after emergence

0 20 40 60 80 100

DE, 2006

0 20 40 60 80 100 120 140

2000

4000

6000

8000

10000DE, 2007

0 20 40 60 80 100 120

MD, 2006

0 20 40 60 80 100 120 140

2000

4000

6000

8000

10000MD, 2007

0 20 40 60 80 100 120 140

Leaf surf

ace a

rea, cm

2 p

lant-1

MD, 2008

Days after emergence

0 20 40 60 80 100 120 140

DE, 2006

0 50 100 150 200

2000

4000

6000

8000

10000DE, 2007

0 50 100 150 200

MD, 2006

0 50 100 150

2000

4000

6000

8000

10000MD, 2007

0 56 112 168

Leaf surf

ace a

rea, cm

2 p

lant-1

MD, 2008

Days after emergence

0 50 100 150

DE, 2006

0 50 100 150 200

2000

4000

6000

8000

10000DE, 2007

0 50 100 150 200

HybridMaize MaizSim AgMaize Obs

Wye 2006 4.9 4.1 4.0 4.1

Wye 2007 4.9 3.9 4.0 4.3

Wye 2008 4.3 3.2 3.6 3.5

Collins 2006 5.4 4.1 4.2 4.2

Collins 2007 5.1 4.2 4.2 4.7

Treatment

LAI

Model

AgMaize HybridM MaizSim

Normal 3.9 5.1 3.9

Normal Avg +3 3.8 5.0 3.7

Normal Avg +6 3.4 5.0 3.4

Treatment

Anthesis Date Maturity Date

Model Model

AgMaize HybridM MaizSim AgMaize HybridM MaizSim

Normal

188.2 193.2 193.6 238.2 242.0 244.4

Normal Avg

+3 178.4 181.0 185.8 222.4 221.6 226.2

Normal Avg

+6 172.0 171.8 180.2 211.4 207.4 214.4

Senescence Impact of stresses

Impact on photosynthesis Plant density effects

Reflects carbon vs. expansion linkage

Light quality relationship

Increasing density can be considered to cause light or carbon stress

VPD vs temperature as a driver for leaf expansion as proposed by Francois Trudeau.

Plant density affects both the quality and quantity of light absorbed by individual leaves

The ratio of shaded to sunlit leaves increases as population increases

There is a change in the ratio of red to far-red light and this impacts leaf growth and photosynthesis

Leaf expansion rate can be adjusted based on the ration of sunlit to shaded leaf fraction

Zhu et al., 2014. Early competition shapes maize whole-plant development in mixed stands. J Exp. Botany. 65:641-653 Here maize was intercropped with wheat. This appears to correspond to the sunlit/shaded leaf fractions and plant population.

Senescence is too slow

We presented three approaches to modeling leaf area in maize

Two models used actual temperatures and employed a non-linear function to calculate temperature effects on leaf addition and expansion

One model used a GDD approach, two models used temperature directly.

All three approaches were able to realistically simulate observed leaf addition rate and leaf area.

Leaf addition rate from growth chambers as a function of temperature seems stable over a wide variety of hybrids. Thus some factors may be general and not have to be calibrated for most situations.

Some calibration/fitting may be necessary to obtain optimal parameters for leaf area expansion for a particular variety. Size of largest leaf and location on the stem is one

of the most critical variables

Total number of juvenile leaves Methods to realistically estimate effects of

temperatures above the optimum are necessary but data for testing may be hard to find.

Role of carbon and leaf water potential Look at plant population effects (carbon effect) Light intensity from growth chambers Carbon interaction with temperature - SLA

Vapor pressure deficit effects on growth even under optimal nutrient and soil water.

Nitrogen effects. How to address interactions such as between

nitrogen and water, or temperature and nitrogen.

Application to tropical varieties.