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17. Leaf photosynthesis In “Ecological Climatology –Concepts and Applications–”

Yoshiyuki Miyazawa (Geography, UH Manoa)

Content of the chapter

1. Light reactions 2. Dark reactions 3. Stomata 4. Net photosynthesis 5. Photosynthesis-transpiration compromise 6. Model 7. Coordinated leaf traits

Physiology; gross photosynthesis

Ecophysiology; net photosynthesis Respiration & photorespiration

Biogeoscience; model prediction

Evolution

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Introduction

Photosynthesis in the terrestrial ecosystem

CO2 Water

Heat

Introduction

Adaptation is the key for the formulation “Plants should choose the most adaptive behavior”

•  Higher photosynthesis •  Efficient resource use (light, water,

nutrient) •  Various strategies & niche separation

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Introduction

Photosynthesis nCO2 + 2nH2O à (CH2O)n + nO2 + nH2O •  2nH2O à 4nH+ + nO2 + 4ne-

・・・・・・・・ •  nCO2 + nRuBP à nPGA

Light reaction

Light reaction

Light

Energy transporter

e- start!

e- goal!

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Dark reaction

Dark reaction (Calvin-Benson cycle)

Whole photosynthesis process

CB cycle

Sugar sugar

Electron transport system

Photosystem

CO2

CO2

Photosynthetic rate (CO2 assimilation rate)

Photosynthetic rate (electron transport rate)

CO 2 CO 2

Photorespiration

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Summary Physiology

•  Photosynthesis is composed of dark and light reactions •  Light reaction provide energy by consuming H2O. •  Dark reaction absorb CO2 using the energy. •  These reactions are in balance with excess supply.

Net photosynthesis

Photosynthesis in the field is reduced by factors

Net photosynthesis = photosynthesis – dark respiration rate

Light Net

pho

tosy

nthe

tic r

ate

Dark respiration rate

Quantum yield

Convexity Amax

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Net photosynthesis

Net photosynthesis = photosynthesis – dark respiration rate

Light Net

pho

tosy

nthe

tic r

ate

A = (αI + Amax )+ (αI + Amax )2 − 4αθAmax

2θ− Rd

Johnson IR, Thornley JHM A model of instantaneous and daily canopy photosynthesis. Journal of Theoretical Biology. 107 4: 531-545. (1984)

Transpira(on  physics  and  biology  process  

Humid  Low  CO2  

CO2  

Water  

Dry  High  CO2  

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Transpira(on  

Ci      ei  

CO2  

Water  

Ca      ea  

Transpira(on        E  =  gsw  (ei-­‐ea)    Photosynthesis      A  =  gsc  (Ca-­‐Ci)        gsw  =  1.58gsc  High  A  requires  high  gs  or  low  Ci  

Can  Ci  decrease  without  limita(on?  

[CO2]  Photosynthesis      A  =  gsc  (Ca-­‐Ci)      gsc  =  A/(Ca-­‐Ci)  =  tanθ    Ph

otosynthesis  

Ca  Ci  

A  

θ  

A =VcmaxCi −Γ

*

Ci +Kc (1+OKo

)− Rd

Farquhar  et  al.  (1980)  

Farquhar GD, Caemmerer SV, Berry JA A biochemical-model of photosynthetic CO2 assimilation in leaves of C-3 species. Planta. 149 1: 78-90. (1980)

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Leaf  water  use  efficiency  (WUE)  The  lower  Ci,  the  more  efficient  for  photosynthesis  

[CO2]  

WUE  =  A/E=                =  

Photosynthesis  

Ca  Ci  

A  

θ  

Ca −Ci1.6(esat − ea )

Air  dryness  &  temperature  

gsc (Ca −Ci )gsw(esat − ea )

Does  Ci  vary  among  species?  Ci  as  the  strategy  for  evolu(on?  

The  value  of  Ci  does  not  differ  much.  

[CO2]  Photosynthesis  

Ci  

Too  low  

Too  high  

Ca  

S. C. Wong, I. R. Cowan & G. D. Farquhar Stomatal conductance correlates with photosynthetic capacity. Nature. 282: 424 - 426. (1980)

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CO2  and  H2O  in  the  trade-­‐off    Ecophysiology  and  adapta7on  

•  Light  and  water  restrict  A  (via  CO2).    •  Vcmax  and  gs  as  the  source  of  varia(on  in  A.  •  Increase  in  gs  increases  both  E  and  A.  •  Ci  is  an  important  factor  for  WUE  but  is  conserved  

among  species    

 The  value  of  carbon  and  water  conflicts…      shade;  nutrient;  drought;  heat  wave  

Let’s  predict  E  and  A!  Restric7ng  gas  exchange  under  variable  environments  

•  A-­‐Ci  rela(onship:  Farquhar  model  •  Ci-­‐gs  rela(onship  •  A-­‐gs  rela(onship  ß  ???  

A =VcmaxCi −Γ

*

Ci +Kc (1+OKo

)− Rd

 A = gsc (Ca-Ci)

gsc = ???  

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The  behavior  of  gs  

sunny  Shaded   Hot  Cold  

Desiccated  Wet   Dry  air  Humid  air  

The  rule  of  gs  Ball-­‐Woodrow-­‐Berry’s  equa(on    

(Ball  et  al.  1987;  Collatz  et  al.  1991)  

gs =m ⋅ArhCs

+ b

Fig. 2

5cm

Miyazawa et al. (Agric. For. Meterol.)

0 50 100 150 200 2500

4

8

12

16(a)

m

Precedent rainfall (mm)

0.2 0.3 0.4

(b)

Soil water content (m3 m-3)A  rh/Cs  

g s   m  

High  light  Humid  

Dark  Evapora(ve  

Collatz GJ, Ball JT, Grivet C, Berry JA Physiological and environmental-regulation of stomatal conductance, photosynthesis and transpiration - a model that includes a laminar boundary-layer. Agricultural and Forest Meteorology. 54 2-4: 107-136. (1991)

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Influence  on  stand  gas  exchange  

Baldocchi DD, Wilson KB, Gu LH How the environment, canopy structure and canopy physiological functioning influence carbon, water and energy fluxes of a temperate broad-leaved deciduous forest-an assessment with the biophysical model CANOAK. Tree Physiology. 22 15-16: 1065-1077. (2002)

Independent  es(ma(on  of  gs  

Hu J, Moore DJP, Riveros-Iregui DA, Burns SP, Monson RK Modeling whole-tree carbon assimilation rate using observed transpiration rates and needle sugar carbon isotope ratios. New Phytologist. 185 4: 1000-1015. (2010) Kostner BMM, Schulze ED, Kelliher FM, Hollinger DY, Byers JN, Hunt JE, McSeveny TM, Meserth R, Weir PL Transpiration and canopy conductance in a pristine broad-leaved forest of Nothofagus - an analysis of xylem sap flow and eddy-correlation measurements. Oecologia. 91 3: 350-359. (1992)

•  Carbon  isotope  (Hu  et  al.  2010)  •  Sap  flow  measurements  

(Kostner  et  al.  1992)  

50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

1.0

DOY

Gs

(mic

rom

ol/m

2/s)

50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

1.0

DOY

Gs

(mic

rom

ol/m

2/s)

50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

1.0

DOY

Gs

(mic

rom

ol/m

2/s)

50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

1.0

DOY

Gs

(mic

rom

ol/m

2/s)

Tap

Tas )( LEDGCA

LEGG

γργ

+Δ−+Δ=

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Modeling  of  gs  

•  Complicate  behavior  of  gs:  so  many  factors  influence  &  interact.  

•  Highly  species-­‐specific.  •  Strong  influence  on  plant-­‐  and  stand  gas  

exchange.  

Leaf  economic  spectrum  Restric(ons  on  the  choice  of  traits  

Costly  leaves  High  photosynthe(c  capacity  

requires  N  

Evans  et  al.  (1989)  

Evans J Photosynthesis and nitrogen relationships in leaves of C3 plants. Oecologia. 78 1: 9-19. (1989)

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Leaf  economic  spectrum  Restric(ons  on  the  choice  of  traits  

The  higher  N  &  the  longer  life,  more  carbon!....  Correct?  

Lifespan-­‐Photosynthesis  trade-­‐off  

Reich PB, Uhl C, Walters MB, Ellsworth DS Leaf life-span as a determinant of leaf structure and function among 23 Amazonian tree species. Oecologia. 86 1: 16-24. (1991)

Leaf  economic  spectrum  Restric(ons  on  the  choice  of  traits  

The  thicker  the  leaf,  the  higher  photosynthe(c  capacity?  

Specific  leaf  area  (SLA)  Leaf  area  /  leaf  mass  

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Leaf  economic  spectrum  Restric(ons  on  the  choice  of  traits  

Species  are  placed  along  the  “spectrum”

nitrogen

Photosynthetic capacity Dark

respiration

SLA Leaf

lifespan

N  

SLA  

Lifespan  (-­‐)  

Glopnet:  collec(on  and  analysis  of  plant  func(onal  types  (PFT)  

•  From  6  con(nents  (Reich  et  al.  1997)  •  All  over  the  world  (Wright  et  al.  2004)  •  Other  traits  (???)  

Reich PB, Walters MB, Ellsworth DS From tropics to tundra: Global convergence in plant functioning. Proceedings of the National Academy of Sciences of the United States of America. 94 25: 13730-13734. (1997) Wright IJ, Reich PB, Westoby M, et al. The worldwide leaf economics spectrum. Nature. 428 6985: 821-827. (2004)

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Leaf  economic  spectrum  

•  High  photosynthesis  and  long  life  is  impossible.  •  Long  life  requires  high  investment  to  the  leaf.  •  Mechanism  underlying  the  rela(onship  (restric(ons)  is  not  clear  even  now.  

•  Excep(ons  are  reported.  

N  

SLA  

Dry  area