Biomass, Mineral Elements and Protein Contents of Six Freshwater Macrophytes from Ghana

Abstract

The biomass, mineral elements and protein contents of six freshwater macrophytes found in Ghana are reported in this paper. The plants are Ceratophyllum demersum (a submerged plant), Eichhornia crassipes and Pistia stratiotes (free-floating plants), Echinochloa pyramidalis and Typha domingensis (emergent plants) and Nymphaea lotus (a floating-leaved plant). The fresh and dry weights of the plants were measured and the concentration of six elements: calcium, magnesium, nitrogen, phosphorus, potassium and sodium in the tissues of the plants were determined. Calcium and magnesium contents were determined by ethylenediamine tetraacetic acid (EDTA) titration, nitrogen by micro-Kjeldahl method, phosphorus as orthophosphate after reaction with molybdate by absorption spectrophotometry, and potassium and sodium by flame photometry. The fresh weight of the plants ranged from 22 to 57 t ha^-1 while the dry weight ranged from 1.2 to 12.5 t ha^-1. Mineral elements varied in the plants as follows: calcium, 0.6–2.2; magnesium, 0.4–2.7; nitrogen, 1.4–3.7; phosphorous, 0.2–0.8; potassium, 0.4–5.2; and sodium, 0.4–3.4 per cent dry weight. These values are within the ranges reported by other workers from comparable freshwater environments. The ethnobotany of the freshwater macrophytes studied was discussed.