1Nadine SchubertInstituto de Ciencias del Mar y Limnología de la UNAM Unidad de Sistemas Arrecifales, Puerto Morelos, México

Part 3:Part 3: Photoprotection Photoprotection

PHOTOBIOLOGY PHOTOBIOLOGY

Part 3:Part 3: Photoprotection Photoprotection

2

LIGHT ABSORPTION UTILIZATION OF ABSORBED LIGHT ENERGY

LIGHT

Light capture

Photochemistry

Production of Oxygen Radicals

Net photodamage

Photodamage

Repair and de novo synthesis

Antioxidant systems

Thermal dissipation Xanthophyll cycle

Adjustment of antenna size State transition

CO2 fixation PhotorespirationWater-water cycleCyclic e-- transportEnergy dissipation

3Irradiance

Pho

tosy

nthe

sis

Photoprotection

Photoinactivation/Photodamage

Excess energy

Fv/Fm

Fv/Fm O2

LIGHT ABSORPTION UTILIZATION OF ABSORBED LIGHT ENERGY

4

XANTHOPHYLL CYCLE

5Antheraxanthin, Lutein

Violaxanthin Zeaxanthin

PHOTOPROTECTION BY CAROTENOIDS

Chlorophyll a

Heat

En

erg

y

6

PS = 0NPQ = 0

PS = 1NPQ = 0

1 PS 01 NPQ 0

PS = 01 NPQ 0

NON-PHOTOCHEMICAL QUENCHING

NPQ = (Fm-Fm’)/Fm’

7

Uhrmacher et al. (1995)

Dictyota dichotoma

Open symbols = light exposure to 150 mol m-2 s-1

Closed symbols = light exposure to 500 mol m-2 s-1

Relationship between ZEA-content and Fv/Fm and NPQ

Garcia-Mendoza & Colombo-Pallotta (2007)

Macrocystis pyrifera

8Müller et al. (2001)

NON-PHOTOCHEMICAL QUENCHING

9

PSIILHCII Cyt bf PSI LHCI

2H2O O2+ 4H+

2H+

PQ

PQH2

2H+

PC

Fd

NADP + H+ NADPH

H+

ATPase

ADP + Pi ATP

1O2

1O2

PHOTODAMAGE

10

PHOTODAMAGE

1Car

3Car*

HEAT

Carotenoids: -carotene- reaction center

3P680*

P680

3O2

1O2*

PSIILHCII

2H2O O2+ 4H+

1O2

11

PHOTODAMAGE

PSIILHCII

2H2O O2+ 4H+

1O2

3Chl*

Chl

3O2

1O2*1Car

3Car*

HEAT Carotenoids: zeaxanthin, lutein

- PSII antennae

1Car

3Car*

HEAT

12

BUT CAREFUL…

CYANOABACTERIA

130

10

20

30

40

50

60

70

80

90

100

P.perforata C.volans P.pacifica C.officinalis

Fm

(%

de

F m e

n f

ar-r

ed)

far-red

oscuridad

BUT CAREFUL…

Determination of Fm is very difficult in red algae due to phycobilisome movement

application of far-red pulse before measurement to ensure that PSII antenna is

associated to PSII

14

BUT CAREFUL…

Campbellet al. (1998)