Shraddha Singh

Potential of Chromolaena odorata for phytoremediation of 137Cs from solution and low level nuclear waste

Potential of Chromolaena odorata plants for remediation of (137)Cs from solutions and low level nuclear waste was evaluated. When plants were exposed to solutions spiked with three different levels of (137)Cs, namely 1 x 10(3) kBqL(-1), 5 x 10(3) kBqL(-1) and 10 x 10(3) kBqL(-1), 89%, 81% and 51% of (137)Cs was found to be remediated in 15 d, respectively. At the lowest Cs activity (1 x 10(3) kBqL(-1)), accumulation of Cs was found to be higher in roots compared to shoots, while at higher Cs activities (5 x 10(3) kBqL(-1) and 10 x 10(3) kBqL(-1)), Cs accumulation was more in shoots than roots. When plants were incubated in low level nuclear waste, 79% of the activity was removed by plants at the end of 15 d. The present study suggests that C. odorata could be used as a potential candidate plant for phytoremediation of (137)Cs.

Copper tolerance and response of antioxidative enzymes in axenically grown Brassica juncea (L.) plants

Copper is an essential element for proper functioning of all living organisms including plants, but it can cause toxicity at elevated concentrations. In the present study, two varieties of Brassica juncea L. i.e. Pusa JK and TM 4 grown axenically were compared for Cu tolerance and accumulation ability. For further detailed biochemical studies, var. TM 4 was used because of its fast growth and better Cu accumulation in shoots. Toxic effects of Cu were manifested by a reduction in photosynthetic pigments and an increase in the levels of thiobarbituric acid reactive substances. The activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and catalase showed an increase in a concentration and exposure time dependent manner in roots of B. juncea exposed to copper, indicating that they play an important role in combating copper stress in this species.

Phytoremediation of Metals and Radionuclides

Phytoremediation is an emerging technology for contaminated sites and is attractive due to its low cost, high public acceptance and environmental friendliness nature. It is not a panacea for all waste problems, but a supplement to the existing technologies. The technology has been demonstrated, but not yet commercially exploited. More research background for development of plant tailored for remediation needs use of genetic engineering. The concept of manipulating plant genes for toxic metal uptake is today a cutting edge research area. The likelihood of public acceptance of genetically engineered plants for phytoremediation will be welcomed, since it will clean up the environment of toxic metals. No doubt phytoremediation technology has attracted a great deal of attention in recent years and it is expected that phytoremediation will capture a significant share of the environmental market in the coming years.

Potential of Vetiveria zizanoides L. Nash for phytoremediation of plutonium (239Pu): Chelate assisted uptake and translocation

Plants have demonstrated a great potential to remove toxic elements from soils and solutions and been successfully used for phytoremediation of important radionuclides. Uptake potential of vetiver plants (V. zizanoides) for the remediation of (239)Pu in hydroponic and soil conditions was studied in the present work. High efficiency of V. zizanoides for the removal of (239)Pu was recorded with 66.2% being removed from the hydroponic solution after 30 days. However, remediation of (239)Pu from soil was limited. Remediation of (239)Pu from soil was increased with the addition of chelating agents citric acid (CA) and diethylenetriaminepentaacetic acid (DTPA). Accumulation of (239)Pu was recorded higher in roots than shoots, however its translocation from roots to shoots increased in the presence of chelators in hydroponic as well as soil conditions. DTPA was found more effective than CA showing higher translocation index (TI). Increase in TI was observed 8 and 6 times in the solution and soil respectively when plants were exposed to (239)Pu-DTPA in comparison to only (239)Pu. The present study demonstrates that V. zizanoides plant is a potential plant for phytoremediation of (239)Pu.

Investigation of arsenic accumulation and biochemical response of in vitro developed Vetiveria zizanoides plants

Vetiver grass (Vetiveria zizanoides L. Nash) is found to be a suitable candidate for the phytoremediation of heavy metals. An investigation of arsenic (As) accumulation, translocation and tolerance was conducted in V. zizanoides plantlets upon exposure to different concentrations of arsenic (10, 50, 100 and 200µM) for 7 and 14 d. V. zizanoides plants were found effective in remediation of As, maximum being at 200µM after 14 d of exposure. The results of TBARS and photosynthetic pigments demonstrated that plants did not experience significant toxicity at all the concentrations of As after 7 days, however an increase in their level was found after 14 d. The up-regulation of antioxidant enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT) and glutathione s-transferase (GST) in a coordinated and complementary manner enhanced tolerance to plants against arsenic induced oxidative stress. Taken together, the results indicated that in vitro developed plants of V. zizanoides have the potential to remediate and tolerate varying levels of As.

Aggregate cell suspension cultures of Psoralea corylifolia improved phytoestrogens production

The intensity of the hydrodynamic stress on cell aggregates is closely related to the growth and production of secondary metabolites. In this study, we have investigated the effects of cell aggregation in suspension cultures of Psoralea corylifolia on growth and phytoestrogens production. HPLC analysis revealed that cell aggregates of 1.2 mm size produced maximum amount of daidzein (2.84% dry wt.) and genistein (0.47% dry wt.) on day 20. The phytoestrogens production level was ~2-fold more than that of heterogeneous cell aggregates (control) in suspension cultures and 11-fold more than field grown plants. Analysis of spent medium revealed no leaching of phytoestrogens. Results indicated that certain degree of cell aggregation in suspension cultures directly supported phytoestrogen production.