Rhizofiltration of hydroponic saline substrates using scented geraniums (Pelargonium sp.)
The ability of scented geraniums ('Pelargonium citrosum' (Citrosa) 'Pelargonium' sp.'Frensham'), to tolerate and accumulate sodium was investigated in a hydroponic system. Chlorophyll ' a' fluorescence kinetics revealed no significant toxic effects on the photosynthetic efficiency of plants in solutions containing up to 100 mM NaCl. Frensham accumulated more sodium than Citrosa geraniums thus were solely used in further experimentation. Sodium accumulation in Frensham was in excess of 3.7 and 2.6% of dry weight in shoots and roots, respectively. Dry mass of tissues decreased with increasing treatments. Sodium accumulation appeared to be affected by seasonal change as uptake decreased with successive trials from January to May 1999. Biochemical analyses of stress related amino acids revealed an initial increase in 4-aminobutyrate, asparagine, glutamine, and alanine in roots with shoot tissues accumulating asparagine, aspartate, and alanine. These data clearly demonstrate that 'Pelargonium' sp. 'Frensham' is a salt tolerant species and a candidate for the remediation of saline solution.