The effect of arsenic on pigment composition and photosynthesis in Hydrilla verticillata

The present study evaluated the effects of 100 and 500 mu M arsenate (Na2HAsO4) on pigment composition and photosynthesis in Hydrilla verticillata (L.f.) Royle. Arsenic accumulation increased in concentration and duration dependent manner. The maximum accumulation [568 mu g(As) g(-1)(d.m.)] was observed at 500 mu M concentration and 96-h exposure. This concentration led to a significant decline in chlorophyll a content and PS II efficiency during the whole experiment, and in chlorophyll b and carotenoids after 96 h, but no significant changes in photosynthetic pigments were noticed at 100 mu M arsenate. Net photosynthetic rate, electron transport rate, and water use efficiency declined whereas transpiration rate increased, and stomatal conductance and photochemical quenching did not show any effect or increased. The content of reactive oxygen species increased and content of reduced ascorbate declined at 500 mu M arsenate in comparison to the control.