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

Does elevated CO₂ protect against photoinhibition in Phillyrea angustifolia at high temperature and low light? Luca Vitale^*,1, Arena Carmen¹, Amalia Virzo De Santo¹, Nicola D'Ambrosio¹, ¹ Dipartimento di Biologia Vegetale, Napoli, Italy.

ABSTRACT- Several studies have shown that elevated CO₂ may reduce the potential for photoinhibition in plants grown at elevated CO₂ by increasing of the photochemical efficiency. The photoprotective role of elevated CO₂ has well been evidenced in plants exposed to high temperatures and saturating irradiances. Little information is available in plants exposed to high temperatures and low irradiances. In this work we assessed the effects of the elevated CO₂ on the PSII photochemical efficiency in plants of Phillyrea angustifolia L. grown at ambient CO₂ and exposed to heat treatments (30 minutes at 40°C) at low light intensity (300 mol photons m^-2 s^-1). The heat treatment was performed at ambient CO₂ (390 ppm) as well as at elevated CO₂ (800 ppm). Gas exchange and chlorophyll fluorescence were measured on leaves before and after exposure to the heat stress at the two CO₂ concentrations. The results showed that the net photosynthesis (A_N) and the quantum yield of PSII electron transport (_PSII) decreased significantly after the heat treatment at both CO₂ concentrations, while no significant differences were found between the two CO₂ treatments after the heat stress. The maximal photochemical efficiency of PSII (F_v/F_m) decreased significantly in both CO₂ treatments, compared to the values measured before of the heat stress, and did not fully recover after 20 h of darkness. Moreover no significant differences in F_v/F_m were found between the two treatments after the heat stress. These data suggest that elevated CO₂ did not reduce the potential for photoinhibition at high temperatures and low light intensity in P. angustifolia.

KEY WORDS: high temperature, elevated CO₂, Phillyrea angustifolia, PSII photochemical efficiency