Sarita Sinha

Optimizing adsorption of crystal violet dye from water by magnetic nanocomposite using response surface modeling approach

A magnetic nanocomposite was developed and characterized. Adsorption of crystal violet (CV) dye from water was studied using the nanocomposite. A four-factor central composite design (CCD) combined with response surface modeling (RSM) was employed for maximizing CV removal from aqueous solution by the nanocomposite based on 30 different experimental data obtained in a batch study. Four independent variables, viz. temperature (10-50°C), pH of solution (2-10), dye concentration (240-400 mg/l), and adsorbent dose (1-5 g/l) were transformed to coded values and a second-order quadratic model was built to predict the responses. The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA) and t-test statistics. Adequacy of the model was tested by the correlation between experimental and predicted values of the response and enumeration of prediction errors. Optimization of the process variables for maximum adsorption of CV by nanocomposite was performed using the quadratic model. The Langmuir adsorption capacity of the adsorbent was determined as 81.70 mg/g. The model predicted maximum adsorption of 113.31 mg/g under the optimum conditions of variables (concentration 240 mg/l; temperature 50°C; pH 8.50; dose 1g/l), which was very close to the experimental value (111.80 mg/g) determined in batch experiment.

Response of higher plants to lead contaminated environment.

Lead concentration is increasing rapidly in the environment due to increased use of its sources by human society. Alarming concentrations of the metal have been reported in dust of densely populated urban areas and, water and land of various areas near the industrial waste disposals. Plants absorb lead and accumulation of the metal have been reported in roots, stems, leaves, root nodules and seeds etc. which increases with the increase in the exogenous lead level. Lead affects plant growth and productivity and the magnitude of the effects depend upon the plant species. Photosynthesis has been found to be one of the most sensitive plant processes and the effect of the metal is multifacial. Nitrate reduction is inhibited drastically in roots by the metal but in the leaves a differential effect is observed in various cultivars. Lead also inhibits nodulation, N-fixation and ammonium assimilation in the root nodules. It appears that the toxic effect of the metal is primarily at physiological level and provision of certain inorganic salts can antagonize the toxic effects to some extent. Further responses of plants to the metal depend on various endogenous, environmental and nutritional factors. Some plants are able to tolerate excess of Pb+2 by involving processes like exclusion, compartmentalization or synthesizing metal detoxifying peptides-the phytochelatins.

Study on arsenate tolerant and sensitive cultivars of Zea mays L.: differential detoxification mechanism and effect on nutrients status.

The study identifies sensitive and tolerant cultivars of Zea mays L. (cv. Azad kamal (AK) and Azad uttam (AU)) towards As(V) induced stress, based upon growth biochemical parameters and metal(loid) levels in a sand culture. As(V) (μgg⁻¹ dw) accumulation was lower in cv. AK (31 ± 1 and 107 ± 30) than cv. AU (34.5 ± 3.3 and 132.6) in leaves and roots, respectively, which correlated with lower levels of malondialdehyde and H₂O₂. No definite trend of Mn, Cu, Zn, Fe, Ca, K and Na accumulation signifies that As(V) has little influence on their uptake. Total chlorophyll and protein levels increased in cv. AK and decreased in cv. AU at 7d. Higher levels of SOD and GR in cv. AK and conversely higher levels of APX, GPX and CAT in cv. AU could be a possible differential detoxification mechanism between the cultivars. The results indicate that cv. AK seems to be arsenate tolerant than cv. AU. We assure that the undertaken study does not involve humans or experimental animals and were conducted in accordance with national and institutional guidelines for the protection of human subjects and animal welfare.

Metal accumulation, growth, antioxidants and oil yield of Brassica juncea L. exposed to different metals

In agricultural fields, heavy metal contamination is responsible for limiting the crop productivity and quality. This study reports that the plants of Brassica juncea L. cv. Pusa bold grown on contaminated substrates [Cu, Cr(VI), As(III), As(V)] under simulated field conditions have shown translocation of metals to the upper part and its sequestration in the leaves without significantly affecting on oil yield, except for Cr and higher concentration of As(V), compared to control. Decrease in the oil content in As(V) treated plants was observed in a dose dependent manner; however, maximum decrease was recorded in Cr treated plants. Among all the metal treatments, Cr was the most toxic as evident from the decrease in oil content, growth parameters and antioxidants. The accumulation of metals was below the detection limit in the seeds grown on 10 and 30 mg kg(-1) As(III) and Cr(VI); 10 mg kg(-1) As(V)) and thus can be recommended only for oil cultivation.

Effect of calcium chloride on heavy metal induced alteration in growth and nitrate assimilation of Sesamum indicum seedlings

Abstract In the early growth phase of Sesamum indicum cv. PB-1, the decrease in fresh and dry mass was higher with 1.0 mM Cd 2+ than with the same level of Pb 2+ and Cu 2+ . Recovery from the metal stress was considerable in the root fresh weight and almost completely in the root dry weight when 10.0 mM (1.9 EC), calcium chloride was supplied to the growing seedlings along with the metal salts in various combinations. Accumulation of Pb 2+ , Cd 2+ and Cu 2+ was differential to the metals and the plant parts when supplied without or with 10.0 mM calcium chloride. The order of endogenous metal accumulation was Cu 2+ Cd 2+ Pb 2+ and roots accumulated more metal than the leaves in the absence, as well as in the presence, of calcium chloride. Calcium chloride could recover loss of in vivo NRA in roots caused by either of the metal combinations, whereas the salt could recover the loss in leaf NRA caused only by Pb 2+ Cd 2+ (1.0 mM each). Response of root and leaf NRA was on the other hand, different when the enzyme was assayed directly using an in vitro assay method, and the salt accelerated the loss in enzyme activity drastically. The organic-N content of root and leaf was, however, increased significantly ( p 2+ , Cd 2+ and Pb 2+ in roots and leaves the metal toxicity is recovered to a great extent in the presence of 10.0 mM calcium chloride in the root environment regarding growth and nitrate reduction of the roots and leaves of young sesame seedlings.

Comparative Evaluation of Metal Phytoremediation Potential of Trees, Grasses, and Flowering Plants from Tannery-Wastewater-Contaminated Soil in Relation with Physicochemical Properties

This study reports a comparative account of metal accumulation in the trees, grasses, and flowering plants from agricultural fields contaminated with tannery wastewater. Soil physico-chemical properties along the pollution gradient and soil depth were analyzed. Monitoring and assessment of the plants growing on contaminated sites revealed that the accumulation of Cr in the aboveground part of the trees ranged from 1.87 to 34.44 μg g−1 dw with maximum concentration in Dendro-calamus strictus (34.44 μg g−1 dw). Chrysanthemum coronarium and Tagetes erecta showed better accumulation of Cr than other flowering plants. Separate field experiments were conducted on the contaminated area. The shoots of Vetiveria zizanoides (532 mg 4 m−2) and Cymbopogan winterianus (535.46 mg 4 m−2) have shown almost similar removal potential of Cr, with maximum removal potential in the roots of C. winterianus (1206.43 mg 4 m−2). Seasonal flowering plants (i.e., C. coronarium) have shown better accumulation of Cr than T. erecta. The results indicate that the plants of V. zizanoides, C. coronarium, and C. winterianus are suitable for phytoremediation of contaminated sites and trees can successfully be used for phytostabilization.

Influence of some growth regulators and divalent cations on the inhibition of nitrate reductase activity by lead in maize leaves

Abstract Substrate induction of in vivo nitrate reductase (NR) activity in excised maize leaf segments from seedlings grown with nutrient containing no nitrogen, was substantially inhibited by 0.5 mM Pb acetate, during a 24 h incubation of leaf segments. Inclusion of IAA, GA 3 , kinetin and salicylic acid in the incubation medium increased NR activity in the absence of Pb, but only GA and salicylic acid did so in the presence of Pb. Salicylic acid negated the inhibitory effect of the Pb, which was related to its concentration. The phenolic acid had little effect on in vitro Pb effects on NR activity. Among CaCl 2 , MgCl 2 , MnCl 2 , ZnCl 2 and CuSO 4 , only MnCl 2 to some extent, negated the inhibitory effect of Pb on in vivo NR activity in the leaf segments, although the chlorides of Ca 2+ , Mg 2+ and Mn 2+ caused some increase in enzyme activity in the absence of Pb. The effect of Mn 2+ caused some increase in enzyme activity in the absence of Pb. The effect of Mn 2+ was concentration dependent. But in vitro supply of MnCl 2 to NR preparation prevented the inhibitory effect of Pb on its activity at each concentration, 5, 10, and 20 mM. The experiments demonstrate that the inhibitory effect of Pb on enzyme activity could be antagonised by salicylic acid and Mn.

Role of sulfate in detoxification of arsenate-induced toxicity in Zea mays L. (SRHM 445): nutrient status and antioxidants

The study highlights the role of sulfur (S) in detoxification of arsenate-induced toxicity and the shift in essential element homeostasis in Zea mays L (SRHM 445). Overall growth of arsenate-treated plants under sulfur starvation (−S) was lower than that in the presence of excess sulfur (+S). Translocation of arsenate from roots to shoots, increased under As(−S) and decreased with As(+S). The level of micronutrients (Cu, Zn, Fe) increased in As(−S) plants. Whereas, the level of K and PO4 was higher in As(−S) plants than in As(+S) plants. Higher malondialdehyde, protein carbonyl, and H2O2 levels in As(−S) plants are indicative of higher oxidative stress. Higher superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities, in As(−S) plants coincided with higher H2O2 levels showing the activity of these enzymes are independent of S availability. Absence of reduced glutathione/oxidized glutathione pool in (−S) plants manifested into failure of ascorbate–glutathione detoxification pathway. Hence, S has dual role of protecting the plant against arsenate-induced toxicity (1) by restricting arsenic (As) translocation to the upper parts and (2) by increasing the activity SOD and APX.

Comparison of two Ferns (Adiantum Capillus-Veneris Linn. and Microsorium Punctatum (Linn.) Copel) For Their Cr Accumulation Potential and Antioxidant Responses

Study was undertaken to compare Cr accumulation in two ferns (Adiantum capillus-veneris Linn. and Microsorium punctatum (Linn.) Copel) and the role of antioxidants were also investigated towards metal tolerance in order to assess the use of ferns in phytomediation/ phytostabilization. Different concentrations (0, 50, 100, 150 μg g−1 dw) of Cr were added to fern planted in pot containing 1 kg soil. In both the ferns, Cr accumulation increased with increase in metal concentration and maximum accumulation of 800.5 μg g−1 (fronds) and 1457.4 μg g−1 (roots) in M. punctatum and 660.8 μg g−1 (fronds) and 1259.6 μg g−1 (roots) in A. capillus-veneris was recorded. The increase in the levels of malondialdehyde, antioxidants and antioxidant enzymes (superoxide dismutase, glutathione peroxidase) in A. capillus-veneris was less pronounced than M. punctatum under Cr exposure as compared to their respective controls. In view of less decrease in chlorophyll content and antioxidants along with higher accumulation of Cr in the fronds M. punctatum, is indicative of its higher tolerance towards Cr. However, bioaccumulation factor (concentration of Cr in fronds/concentration of Cr in the soil) of both the ferns was recorded > 1 which qualifies the plants as potential Cr hyperaccumulator and suitable for phytoremediaton.

Effect of chromium on accumulation and antioxidants in Cucumis utillissimus L.: response under enhanced bioavailability condition.

This study compares the accumulation of Cr(VI) and biochemical changes (total chlorophyll, carotenoid, protein, malondialdehyde (MDA) and cysteine contents) and roles of antioxidant enzymes (superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX)) in tolerance to metal induced stress in Cucumis utillissimus L. grown in Cr contaminated soil (CS) with garden soil (GS). Furthermore, Cr bioavailability was enhanced by ethylene diamine tetra-acetic acid (EDTA) addition to the soil to forecast the plants accumulation pattern at elevated Cr environment. Accumulation of Cr in the leaves of the plant increased with increase in substrate metals concentration. It further increased with the addition of EDTA by 1437% and 487% in GS and CS, respectively at the highest treatment level. The lipid peroxidation increased proportionately with increase in Cr accumulation in the leaves. All the activity of antioxidant enzymes (SOD, GPX and APX) and the level of cysteine increased with dose dependant manner. SOD and cysteine were observed to be higher in the GS than in CS, but APX and GPX were found to be higher in CS than in GS. The increase in GPX and APX activities with the increase in Cr concentration could be assumed that these two enzymes have a major role in the defense mechanism towards stress induced by Cr in C. utillissimus.