1 Nadine Schubert Instituto de Ciencias del Mar y Limnología de la UNAM Unidad de Sistemas Arrecifales, Puerto Morelos, México Part 3: Photoprotection PHOTOBIOLOGY

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 CO 2 fixation Photorespiration Water-water cycle Cyclic e - - transport Energy dissipation

3 Irradiance Photosynthesis Photoprotection Photoinactivation/Photodamage Excess energy  F v /F m  O 2 LIGHT ABSORPTION  UTILIZATION OF ABSORBED LIGHT ENERGY

4 XANTHOPHYLL CYCLE Violaxanthin Cycle Yamamoto et al., (1962)

5 Energía S1S1 S2S2 Violaxantina Qy Clorofila a Accessory pigment Energy collector S1S1 Zeaxantina Calor S0S0 Protective pigment Energy dissipater Antheraxanthin, Lutein Violaxanthin Zeaxanthin PHOTOPROTECTION BY CAROTENOIDS Chlorophyll a Heat Energy

6 PS = 0 NPQ = 0 PS = 1 NPQ = 0 1  PS  0 1  NPQ  0 PS = 0 1  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

8 Müller et al. (2001) NON-PHOTOCHEMICAL QUENCHING

9 PSII LHCII Cyt bfPSILHCI 2H 2 OO 2 + 4H + 2H + PQ PQH 2 2H + PC Fd NADP + H + NADPH H+H+ ATPase ADP + Pi ATP 1O21O2 1O21O2 PHOTODAMAGE

10 PHOTODAMAGE 1 Car 3 Car * HEAT  Carotenoids:  -carotene - reaction center 3 P680* P680 3O23O2 1O2*1O2* PSII LHCII 2H 2 OO 2 + 4H + 1O21O2

11 PHOTODAMAGE PSII LHCII 2H 2 OO 2 + 4H + 1O21O2 3 Chl* Chl 3O23O2 1O2*1O2* 1 Car 3 Car * HEAT  Carotenoids: zeaxanthin, lutein - PSII antennae 1 Car 3 Car * HEAT

12 BUT CAREFUL… CYANOABACTERIA RED ALGAE GREEN ALGAE, HIGHER PLANTS

13 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)