Deschampsia antarctica Desv. primary photochemistry performs differently in plants grown in the field and laboratory

Abstract

Primary photochemistry of photosystem II (Fv/Fm) of the Antarctic hair grass Deschampsia antarctica growing in the field (Robert Island, Maritime Antarctic) and in the laboratory was studied. Laboratory plants were grown at a photosynthetic photon flux density (PPFD) of 180 μmol m−2 s−1 and an optimal temperature (13 ± 1.5°C) for net photosynthesis. Subsequently, two groups of plants were exposed to low temperature (4 ± 1.5°C day/night) under two levels of PPFD (180 and 800 μmol m−2 s−1) and a control group was kept at 13 ± 1.5°C and PPFD of 800 μmol m−2 s−1. Chlorophyll fluorescence was measured during several days in field plants and weekly in the laboratory plants. Statistically significant differences were found in Fv/Fm (=0.75–0.83), F0 and Fm values of field plants over the measurement period between days with contrasting irradiances and temperature levels, suggesting that plants in the field show high photosynthetic efficiency. Laboratory plants under controlled conditions and exposed to low temperature under two light conditions showed significantly lower Fv/Fm and Fm. Moreover, they presented significantly less chlorophyll and carotenoid content than field plants. The differences in the performance of the photosynthetic apparatus between field- and laboratory-grown plants indicate that measurements performed in ex situ plants should be interpreted with caution.