Growth and photosynthetic responses to copper stress of an invasive cordgrass, Spartina densiflora.

Spartina densiflora Brongn. is found in coastal marshes of south-west Spain, growing in sediments with between 300 and 3000mg Cu kg(-1) total soil DW (450-4500mg Cu kg(-1) supposing that the soil porosity is 0.5). An experiment was designed to investigate the effect of copper from 0 to 5000mgkg(-1) (64mmoll(-1)) on the photosynthetic apparatus and the growth of S. densiflora. We also determined total ash, copper, calcium, magnesium and phosphorous concentrations, as well as C/N ratio. S. densiflora survived to concentrations as high as 320mg Cukg(-1) DW in leaves, although excess of Cu diminished water use efficiency and Ca-, Mg- and P-uptake. Also, quantum efficiency of PSII, net photosynthetic rate, stomatal conductance and pigment concentrations declined with increasing external Cu. Finally, the decline in the photosynthetic function resulted in a biomass reduction of between 50 and 80% (for 600 and 5000mg Cu kg(-1), respectively).