PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

Photoprotective role of anthocyanins regulating PSII activity of Setcreasea purpurea exposed to excessive light energy. David Dewez^*,1, Philippe Juneau², Radovan Popovic¹, ¹ University of Quebec in Montreal, Montreal, Quebec, CANADA² University of British Columbia, Vancouver, British Columbia, CANADA

ABSTRACT- Accumulation of anthocyanins in plant leaf appeared when plants are exposed to excessive light energy. In this study, we presented the experimental evidence for anthocyanins to have important regulatory role in the determination of PSII primary photochemistry. The experiments were done with ornamental plant Setcreasea purpurea able to grow either under extremely low light intensity (10-20 mol) where anthocyanins synthesis was not present (green appearing leaves) and under strong light intensity (400 mol) inducing anthocyanins accumulation in leaf epidermis cell layer. We investigated the effect of anthocyanins on the functional state of PSII reaction centers by comparing photosynthetic activity of green and red leaves, and red leaf without epidermis containing anthocyanins. Red and green leaves exposed to high-energy illumination flux were performing photosynthetic activity very differently. Under low light intensity, red leaves whose epidermis was removed had very similar photosynthetic performance compared to those from green leaves. We found for red leaves without epidermis to show a photoinhibitory effect when they have been exposed to high light intensity. In those leaves, functional PSII quantum yield was diminished by 4 times, Q_P by 2 and half, and Q_N by twice when compared to red leaves containing anthocyanins. This regulation also affects the mechanism of absorbed light energy dissipation in leaves via non-photochemical pathways and consequently provides better conditions for plant to avoid photodamage. Leaves of S. purpurea contain active, inactive or dissipative PSII forms which may convert from one to another by the presence of anthocyanins. We concluded that anthocyanins epidermis filter formed under strong light intensity regulate PSII electron transport by maintaining PSII reaction centers in open states. Our experimental data showed for PSII reaction centers are in open and closed state when anthocyanins filter was present and absent respectively, therefore, this may prevent photoinhibition induced by excessive light energy.

KEY WORDS: Photosystem II, Anthocyanins, Chlorophyll fluorescence, Photoinhibition