Comparison of synthetic and organic biodegradable chelants in augmenting cadmium phytoextraction in Solanum nigrum.

This study focused to enhance the cadmium (Cd) phytoextraction efficiency in Solanum nigrum by applying four biodegradable chelants (10 mM)-ethylene glycol tetraacetic acid (EGTA), ethylenediamine disuccinate (EDDS), nitrilotriacetic acid (NTA), and citric acid (CA), when grown in Cd-spiked soil (12 and 48 mg kg-1). Plant height, dry biomass, photosynthetic traits, and metal accumulation varied significantly with Cd and chelant treatments. Cadmium-toxicity resulted in reduction of plant growth and photosynthetic physiology, whereas chelant supplementation alleviated the toxic effect of Cd and increased its accumulation. Tolerance index value increased with addition of chelants in the order: EGTA (1.57-1.63) >EDDS (1.39-1.58) >NTA (1.14-1.50) >CA (1-1.22) compared with Cd (0.46-1.08). Transfer coefficient of root increased with supplementation of EGTA (3.40-3.85), EDDS (3.10-3.40), NTA (2.60-2.90), and CA (1.85-2.29), over Cd-alone (1.61-1.63). Similarly, translocation factor was also increased upon addition of EGTA (0.52-0.73), EDDS (0.35-0.81), NTA (0.38-0.75), and CA (0.53-0.54), compared with Cd-alone (0.36-0.59). Maximum Cd removal (67.67% at Cd12 and 36.05% at Cd48) was observed with supplementation of EGTA. The study concludes that the supplementation of EGTA and EDDS with S. nigrum can be employed as an efficient and environmentally safe technique for reclamation of Cd-contaminated soils.

Apart from the selection of a good hyperaccumulator, the choice of chelant (biodegradable/non-biodegradable) is an important aspect for the successful phytoextraction of metals from contaminated soil. We reported for the first time the potential of ethylene glycol tetraacetic acid (EGTA; a biodegradable chelant) in enhancing Cd phytoextraction by Solanum nigrum. Comparative appraisal of metal extraction efficiency of biodegradable chelants at low (12 mg kg⁻¹) and high (48 mg kg⁻¹) Cd dose depicted that EGTA performed better than EDDS, NTA, and CA (other biodegradable chelants). EGTA supplementation did not induce toxicity in plants; rather it improved metal accumulation, morphology, and photosynthetic physiology.

Biodegradable chelant-metal complexes enhance cadmium phytoextraction efficiency of Solanum americanum.

Toxic contaminants (metals and metal-containing compounds) are accumulating in the environment at an astonishing rate and jeopardize human health. Remarkable industrial revolution and the spectacular economic growth are the prime causes for the release of such toxic contaminants in the environment. Cadmium (Cd) is ranked the 7th most toxic compound by the Agency for Toxic Substances and Disease Registry (USA), owing to its high carcinogenicity and non-biodegradability even at miniscule concentration. The present study assessed the efficiency of four biodegradable chelants [nitrilotriacetic acid (NTA), ethylenediamine disuccinate (EDDS), ethylene glycol tetraacetic acid (EGTA), and citric acid (CA)] and their dose (5 mM and 10 mM) in enhancing metal accumulation in Solanum americanum Mill. (grown under 24 mg Cd kg-1 soil) through morpho-physiological and metal extraction parameters. Significant variations were observed for most of the studied parameters in response to chelants and their doses. However, ratio of root and shoot length, and plant height stress tolerance index differed non-significantly. The potential of chelants to enhance Cd removal efficiency was in the order - EGTA (7.44%) > EDDS (6.05%) > NTA (4.12%) > CA (2.75%). EGTA and EDDS exhibited dose-dependent behavior for Cd extraction with 10 mM dose being more efficient than 5 mM dose. Structural equation model (SEM) depicted strong positive interaction of metal extraction parameters with chelants (Z-value = 11.61, p = 0.001). This study provides insights into the importance of selecting appropriate dose of biodegradable chelants for Cd extraction, as high chelant concentration might also result in phytotoxicity. In the future, phytoextraction potential of these chelants needs to be examined through field studies under natural environmental conditions.

Characterization and antioxidant activity of essential oils from fresh and decaying leaves of Eucalyptus tereticornis.

The composition of essential oils hydrodistilled from fresh and decaying leaves of Eucalyptus tereticornis was analyzed by means of gas chromatography and mass spectrometry, and a total of 68 constituents were identified. The essential oils were assayed for antioxidant activity in terms of scavenging of 2,2-diphenyl-1-picrylhydrazil (DPPH) and hydroxyl (OH(*)) radical, and superoxide anion (O2(-*)).The major constituents of the fresh leaf oil were alpha-pinene (28.53%) and 1,8-cineole (19.48%), whereas in the decaying leaf oil, beta-citronellal (14.15%), (-)-isopulegol (13.35%), and (+)-beta-citronellol (10.73%) were the major components. Both essential oils exhibited a strong radical scavenging activity against DPPH radical with IC50 values of 110 and 139.8 microg/mL for fresh and decaying leaf oil, respectively (IC50 of BHT = 164.2 microg/mL). Further, the essential oils (at 400 microg/mL) also exhibited OH(*) (56-62%) and O2(-*) (65-69%) scavenging activity parallel to the commercial antioxidant BHT/ascorbic acid. However, unlike the essential oils, the major monoterpene constituents exhibited significantly less scavenging activity (<35% DPPH or OH(*); at 400 microg/mL). The study concluded that fresh and decaying leaves of E. tereticornis are a source of monoterpenoid rich oil exhibiting antioxidant activity.