BackgroundLead (Pb) heavy metal pollution in water bodies is one of the serious problems across the world. This study was designed to find out the effect of Pb toxicity on physiological and biochemical changes in Eichhornia crassipes (water hyacinth) seedlings.ResultsThe plant growth was significantly inhibited (50%) at 1000 mg/L Pb concentration. Accumulation of Pb was higher in root than in shoot tissues. The maximum level of Pb accumulation was noticed in roots (5.45%) followed by petiole (2.72%) and leaf tissues (0.66%). Increasing the Pb concentration gradually decreased the chlorophyll content. Intracellular distribution of Pb was also studied using SEM-EDX, where the Pb deposition was observed in both root and leaf tissues. MDA content increased in both the leaf and root tissues up to the 400 mg/L Pb treatment and slightly decreased at higher concentrations. The activity of antioxidative enzymes, such as APX and POX, positively correlated with Pb treatment, while in the case of SOD and CAT enzymes increased up to 800 mg/L treatment and then slightly decreased at higher concentration in both leaf and root tissues.ConclusionsThese results suggest that water hyacinth plants have efficient mechanism to tolerate Pb toxicity, as evidenced by an increased level of antioxidative enzymes. Results clearly indicate that water hyacinth is a feasible plant for hyperaccumulation of heavy metals from polluted wetlands.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-014-0054-6) contains supplementary material, which is available to authorized users.

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Mercury (Hg) is one of the major toxic heavy metals because it bioaccumulates and biomagnifies in animal and human bodies via the food chain. To eliminate heavy metal contamination, plants are being used as removal agents of pollutants/toxic chemicals from the environment. The present study was mainly focused on elucidating the potential phytotoxic effects of Hg heavy metal ion exposure on Sesbania grandiflora seedlings. Growth of seedlings was significantly affected (56 %) at 60 mg L -1 Hg concentration. The level of chlorophyll pigment contents was increased in Hg-treated plants compared to the control. Malondialdehyde content and antioxidative enzyme activities were found to be significantly increased by increasing the concentration of Hg exposure up to 40 mg L -1 while slightly decreased at higher doses. The DNA alterations appearing in the random amplified polymorphic DNA (RAPD) profiles of leaf and root tissues following Hg heavy metal exposure included the disappearance of normal DNA bands and the appearance of new bands compared to the untreated controls. This result strongly indicated that genomic template stability was significantly affected by Hg-induced stress in S. grandiflora seedlings. It is concluded that DNA polymorphisms detected by RAPD fingerprinting analysis could be used as potential molecular markers for the evaluation of Hg heavy metal ion-induced genotoxic effects in other plant species.

Mercury heavy metal pollution has become an important environmental problem worldwide. Accumulation of mercury ions by plants may disrupt many cellular functions and block normal growth and development. To assess mercury heavy metal toxicity, we performed an experiment focusing on the responses of Eichhornia crassipes to mercury-induced oxidative stress. E. crassipes seedlings were exposed to varying concentrations of mercury to investigate the level of mercury ions accumulation, changes in growth patterns, antioxidant defense mechanisms, and DNA damage under hydroponics system. Results showed that plant growth rate was significantly inhibited (52 %) at 50 mg/L treatment. Accumulation of mercury ion level were 1.99 mg/g dry weight, 1.74 mg/g dry weight, and 1.39 mg/g dry weight in root, leaf, and petiole tissues, respectively. There was a decreasing trend for chlorophyll a, b, and carotenoids with increasing the concentration of mercury ions. Both the ascorbate peroxidase and malondialdehyde contents showed increased trend in leaves and roots up to 30 mg/L mercury treatment and slightly decreased at the higher concentrations. There was a positive correlation between heavy metal dose and superoxide dismutase, catalase, and peroxidase antioxidative enzyme activities which could be used as biomarkers to monitor pollution in E. crassipes. Due to heavy metal stress, some of the normal DNA bands were disappeared and additional bands were amplified compared to the control in the random amplified polymorphic DNA (RAPD) profile. Random amplified polymorphic DNA results indicated that genomic template stability was significantly affected by mercury heavy metal treatment. We concluded that DNA changes determined by random amplified polymorphic DNA assay evolved a useful molecular marker for detection of genotoxic effects of mercury heavy metal contamination in plant species.