Metal accumulation, growth and nutrition of Vernonia polyanthes exposed to lead nitrate and arbuscular mycorrhizal fungi

The association between plants and arbuscular mycorrhizal fungi (AMF) can be used to bioremediate areas contaminated by metals. The objectives of this work were to evaluate the lead (Pb2+) phytoaccumulation capacity, morpho-physiology and nutrition responses of Vernonia polyanthes exposed to a solution amended with concentrations of lead nitrate and arbuscular mycorrhizal fungi. The treatments consisted of increasing doses of Pb2+ as lead nitrate [Pb(NO3)2], two strains of AMF and an absolute control without lead and AMF. Lead negatively affected some morphophysiological variables, reduced 27.3, 25.63, 30.60, and 56.60% shoot length, root collar diameter, number of leaves and leaf area, respectively, besides reducing decreasing chlorophyll a. Lead accumulated in the shoot and roots, the latter at the highest concentrations. However, the translocation factor was above 1, indicating low efficiency. The bioaccumulation factor referring to the roots were above 1. The fungi colonization rate was low, 3.31% for Gigaspora margarita and 2.33% for Acaulospora morrowiae. However, the absorption of lead increased, reflecting in lower values of chlorophyll a, dry mass of root and diameter. Results indicated that the arboreal species V. polyanthes tolerate high concentrations of lead and can accumulate significant amounts in the roots. AMF increase the accumulation of lead in the shoot and can be used in projects aimed at the phytoextraction of metals.

Effects of applied cadmium on its accumulation, dry matter production and net photosynthesis in okra and amelioration of cadmium toxicity through lime application

Aim: Vegetables grown in cadmium contaminated soils accumulate cadmium in their tissues and are risky for consumption. The aim of the study was to get an insight into the effect of different levels of cadmium in soil, on accumulation in different plant parts of okra and its effect on overall growth, biomass production and photosynthesis rate so that suitable management option is explored to produce safe vegetable in cadmium contaminated soils. Methodology: The study was conducted in replicated pots with three soil pH (5.46, 6.54 and 7.45) attained through addition of CaCO3 as main treatment and four Cd levels viz., 0, 3, 6 and 9 mg kg-1 of soil as sub-treatment. Okra (Abelmoschus esculentus) was taken as the test crop. The experiment was conducted in a net house. Results: The Cd concentrations were minimum in fruits (0.54, 0.31 and 0.14 mg kg-1) and higher in leaves at acidic pH (5.5), while in soil limed to slightly acidic (6.5) and alkaline pH (7.5) roots retained maximum Cd among plant parts. Net photosynthesis and biomass production decreased significantly with higher Cd doses at acidic pH (5.5). The rate of decline in net photosynthesis was lesser at higher soil pH. The transfer factors decreased with increase in soil pH. The DTPA extractable soil Cd decreased from 8.5 to 2% when soil pH increased rendering the Cd less available for plant uptake. Interpretation: Liming can be an effective ameliorative measure to mitigate Cd toxicity in acidic soils and can ensure safe consumption. Lowest accumulation of cadmium in fruit part suggests okra to be a potential vegetable crop for Cd polluted soils.

Accumulation of metals in selected macrophytes grown in mixture of drain water and tannery effluent and their phytoremediation potential.

Phytoremediation is an emerging, ecofriendly and economically feasible technique for the restoration of heavy metals contaminated environment. In the present investigation, five native macrophytes growing naturally in a drain receiving tannery effluent viz Bacopa monnieri, Eichhornia crassipes, Hydrilla verticillata, Ipomoea aquatica and Marsilea minuta were evaluated for their heavy metal (Cr, Cu, Ni and Pb) accumulation potential in field conditions at Unnao, U.P., India. The results showed that metal accumulation by these macrophytes differed among species and tissue parts. The concentration of Cr, Cu, Ni and Pb in the root tissues were estimated in the range 3.38 -45.59, 1.01 -16.85, 1.81-4.43 and 1.02 -4.24 µg g-1 d.wt., whereas the corresponding shoot values were 8.79 -48.81, 1.01-8.67, 0.84 -2.89 and 1.02 -2.84 for Cr, Cu, Ni and Pb respectively. Among the studied plants the translocation factor (TF) ranged between 1.07-2.60, 0.75-3.83, 1.44-2.57 and 0.49-3.76 for Cr, Cu, Ni and Pb, respectively. The highest metal TF was found in M. minuta (2.60, 3.83 and 2.57) for Cr, Cu and Ni respectively, whereas Pb was best translocated (3.76) by B. monnieri. Roots and shoots of the studied macrophytes showed a value of greater than 1 for metal enrichment coefficient. Findings suggest that E. crassipes can be used for phytoremediation of Cu and Ni whereas M. minuta and H. verticillata can be applied for the removal of Cr and Pb respectively from the contaminated water bodies.

Accumulation and translocation of heavy metals in soil and plants from fly ash contaminated area.

The present investigation deals with the accumulation of heavy metals in fields contaminated with fly ash from a thermal power plant and subsequent uptake in different parts of naturally grown plants. Results revealed that in the contaminated site, the mean level of all the metals (Cd, Zn, Cr, Pb, Cu, Ni, Mn and Fe) in soil and different parts (root and shoots) of plant species were found to be significantly (p<0.01) higher than the uncontaminated site. The enrichment factor (EF) of these metals in contaminated soil was found to be in the sequence of Cd (2.33) > Fe (1.88) > Ni (1.58) > Pb (1.42) > Zn (1.31) > Mn (1.27) > Cr (1.11) > Cu (1.10). Whereas, enrichment factor of metals in root and shoot parts, were found to be in the order of Cd (7.56) > Fe (4.75) > Zn (2.79) > Ni (2.22) > Cu (1.69) > Mn (1.53) > Pb (1.31) > Cr (1.02) and Cd (6.06) ~ Fe (6.06) > Zn (2.65) > Ni (2.57) > Mn (2.19) > Cu (1.58) > Pb (1.37) > Cr (1.01) respectively. In contaminated site, translocation factor (TF) of metals from root to shoot was found to be in the order of Mn (1.38) > Fe (1.27) > Pb (1.03) > Ni (0.94) > Zn (0.85) > Cd (0.82) > Cr (0.73) and that of the metals Cd with Cr, Cu, Mn, Fe; Cr with Pb, Mn, Fe and Pb with Fe were found to be significantly correlated. The present findings provide us a clue for the selection of plant species, which show natural resistance against toxic metals and are efficient metal accumulators.