Physiological responses of Salvinia minima to different phosphorus and nitrogen concentrations

This study was designed to evaluate the effectiveness of salvinia (Salvinia minima) in accumulating nitrogen and phosphorus under different imitating eutrophic environments. Nitrogen concentrations of 1.0 (control), 10.0, and 100 mg/l and phosphorus concentrations of 0.1 (control), 1.0, and 10.0 mg/l were used in this study. Plants were grown under laboratory conditions at 25 +/- 2 degrees C with a light intensity of 120 mu mol/m(2)/s, and a 14 hr photoperiod. Salvinia's growth, expressed as frond production and plant fresh weight doubling time, was significantly increased with increasing nitrogen concentration from 1.0 mg/l to 100.0 mg/l in the growth media. The increase in growth rate was independent from the variation in phosphorus concentrations. However, the highest growth rate was obtained for days 1 through 7 when the levels of both nitrogen and phosphorus were elevated 100 fold (100 mg/l N and 10.0 mg/l P) from that of control treatments. This treatment also resulted in the highest photosynthetic rate, chlorophyll a and b content, carotenoids and anthocyanins concentrations. Nitrogen and phosphorus concentration did not influence soluble sugar (SS) accumulation. Starch and total-nonstructural carbohydrate (TNC) accumulation was significantly lower in treatments receiving elevated levels of nitrogen or phosphorus when compared to the control. The highest uptake of nitrogen and phosphorus into plant tissues resulted when both nutrients were elevated 100 fold (100 mg/l N and 10.0 mg/l P) and were higher at day 14.