Nickel is an essential element for normal physiological functions in plants. At higher doses (>50 mg/kg, as per WHO) it is toxic to plants and humans, which can bring about oxidative stress affecting the physiological functions of plants and is also considered carcinogenic to human beings. To manage nickel pollution in environment, proper chemical or phytoremediation techniques are required. In this regard nickel accumulator plants would offer a cost effective and environmental friendly phytoremediation method. In the present study, the nickel phyto-accumulation potential of Amaranthus viridis from soil was evaluated to check the tolerance level and the impact on selected morphological parameters like total biomass, plant height, root length and number of leaves. Nickel uptake by A. viridis was studied from Ni contaminated soil amended with20, 40, 60, 80 mg/Kg of Ni exposure under controlled conditions. Toxic effects and tolerance of the plant to toxic doses of nickel was evaluated by correlating the uptake per gram of biomass with various parameters of plant like its height, biomass, root length and, number of leaves. Supply dependent maximum nickel uptake of 108 µg/gm and corresponding decrease in growth parameters were recorded up to 60 mg/Kg exposure. This study indicates the uptake of nickel by A. viridis increases with increase in supply up to 60mg/kg and beyond 60 mg/kg, the uptake decreases. The study also shows uptake of nickel per gram of biomass has a significant negative correlation mainly with parameters like plant height (R= -0.71 at 0.05 level of significance) and total biomass (R = -0.83 at 0.05 level of significance) where as other parameters like length of root and number of leavers are not significantly affected (P>0.05) with uptake of nickel per gram of biomass.
Aquatic plants with their high relative growth rates efficiently absorb nutrients from their surrounding media, thereby providing a simple and inexpensive solution for nutrient-polluted aquifers. The present study determined the P accumulation efficiencies of four different aquatic plants namely, Eleocharis plantaginea, Eichhornia crassipes, Pistia stratiotes, and Hydrilla verticillata from the 6043 ha Kabar Wetland (86• 05 E to 86• 09 E, 25• 30 N to 25• 32 N). The aim of the study was to select the most efficient P accumulator. Water, sediment, and plant samples from Kabar were monthly analyzed for P content for 13 months from July 2009 to July 2010. Pistia stratiotes L. accumulated the highest amount of tissue P (1.06 ± 0.22 mg/g dw). The maximum capacity of luxury uptake of P under greenhouse conditions as exhibited by Pistia was further tested. Pistia individuals tolerated up to 50 mg/L phosphate medium and accumulated 6.12 ± 0.95 mg/g dw P after 35 days under greenhouse conditions. Up to 91% phosphate was removed from the surrounding medium within 60 days at 50 mg/L supply. Tissue P levels increased with increasing phosphate levels in the surrounding media but variation with incubation period was statistically insignificant. Our studies present Pistia as more efficient than other common wetland species like Eichhornia, Phragmites, Typha, and so forth when grown in the sub-tropics and confirm its ability to ameliorate P-polluted subtropical wetlands.
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