Aluminium accumulation in excess and related anti-oxidation responses in C4 weed (Amaranthus viridis L.).

C4 species, Amaranthus viridis L. exhibited a significant bioaccumulation of aluminium (Al) through the duration of 3- and 5-days exposure. As compared to control, Amaranthus appeared as excess-accumulator with maximum 5.85-fold bioaccumulation of Al in root. Cellular responses to Al tolerance initially scored tissue specific distribution of metal through cortical layers revealed by electron microscopy. The affected cells changed an oxidative status as read by histochemical stains, particularly, for hydrogen peroxide. Osmotic stress and its stability were scored by maximum proline and free amino acids accumulation with 1.53 and 1.59-fold increase over control. The accumulation of phenolics and flavonoids were over expressed in the ranges of 2.48-2.50-fold and 2.00-1.5-fold at 3- and 5-days respectively against control. Anti-oxidation to detoxify Al stress was facilitated by variants of peroxidases. For exclusion mechanism of metal, esterase activity significantly over expressed with maximum value of 1.80-fold at 5-days. The polymorphism of esterase exhibited few significant over produced bands, varied in numbers as detected by densitometric scanning. Moreover, plant extract was satisfactorily potential under in vitro anti-oxidation systems through assay of 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS), ferric chelation activity etc. Therefore, weeds like Amaranthus would be a bioprospecting in role likely involved in phytoremediation of metal.

Moderation of physiological responses in rice plants with Azolla under 2,4-Dichlorophenoxy acetic acid stress.

The present work highlights some preliminary observations on metabolism in rice (Oryza sativa Linn.) when an aquatic fern Azolla pinnata R.Br. was co-cultured under 2,4-Dichlorophenoxy acetic acid toxicity. We have observed the effects of Azolla in both fresh and dried forms. This work signifies the possible physiological changes of a crop plant by using Azolla as a bioremediator. In brief the herbicide 2,4-D is considered as stressor to rice plants and by applying the fresh and dried Azolla we investigate the changes occurred. The activities of different nitrogen metabolizing enzymes and reactive oxygen species were observed. On the other hand chlorophyll and carotenoids synthesis were retrieved by addition of fresh and dried Azolla mass over 2,4-D toxicity. Thus, the efficiency of fresh and dried Azolla mass was evaluated under herbicidal toxicity in rice. We evaluate the bio remediating role of Azolla plants against 2,4-D stress and conclude this species would also be supporting in supplementation of major nutrients to rice plants.

Antioxidative responses of Salvinia (Salvinia natans Linn.) to aluminium stress and it's modulation by polyamine.

Antioxidative stress response of free-floating aquatic fern (Salvinia natans Linn.) was studied under increasing toxic amount of aluminium (Al) and its modulation by exogenous application of polymaine. Increased levels of superoxide (O2 (-)) and hydrogen peroxide (H2O2) species from affected tissues suggested that plants were undergoing oxidative stress and it was concominant with increased accumulation of Al in a dose dependent manner. Application of polyamine like putrescine (Put) led to a decrease in oxidative stress as revealed by reduced level of O2 (-) and H2O2. Al toxicity resulted into decreased biomass that was ameliorated by the application of Put. The changes observed in lipid peroxidation (MDA) and protein oxidation also indicated that plats are undergoing Al induced oxidative stress. In order to circumvent the oxidative stress resulting from Al toxicity, plants enzymatic and nonenzymatic antioxidant pathways were active. The ratio of both oxidized and reduced cellular glutathione exhibited significant variation in response to Al stress and was improved upon Put treatment. Peroxidase and glutathione were upregulated whereas catalse was downregulated under varying doses of Al. Isozyme profile of above enzymes also showed a trend with increasing amount of Al. The nuclear disintegration study using comet assay was indicative of Al induced oxidative stress. In the present study, we have explored the antioxidative response of aquatic fern Salvinia natans Linn in response to Al toxicity. The application of polyamine Put improved the overall antioxidative response and thus would make it a better candidate to be used as hyper accumulator of Al and other toxic metals.

Variations of antioxidative responses in two rice cultivars with polyamine treatment under salinity stress.

The rice varieties viz. Nonabokra and Swarna were evaluated on the basis of their responses for oxidative stress induced by sodium chloride (NaCl) and the effects of exogenously applied polyamine thereon. Rice seedlings were treated with 200 mM of NaCl supplemented with two dosages: 1 mM and 2 mM putrescine. Following treatments, plants were evaluated for accumulation of reactive oxygen species (ROS) like O2 (-), H2O2 etc. in tissues, lipid peroxidation, protein carbonylation, accumulation of flavonoids and anthocyanin, activities of different oxidative enzymes like guaiacol peroxidase (GPX), catalase (CAT) and glutathione reductase (GR). Preliminary, oxidative stress out of salinity was ensured by plants from significantly higher accumulation of O2 (-) and H2O2 in the tissues of the NaCl treated varieties. Irrespective of varieties, there recorded a significant variation of the endogenous polyamine profiles under NaCl stress. Interestingly, exogenous application of putrescine had a close relationship on O2 (-) and H2O2 content for both the varieties. However, Nonabokra was evident as more respondent than Swarna to applied putrescine. The other effects of oxidative stress was impacted on plants as higher values of MDA content, enhanced rate of protein oxidation and putrescine recorded as an alleviating agent regardless of varieties with dose dependant manner. The generation of ROS and cellular disintegration was accompanied by up regulation of non-enzymatic and enzymatic antioxidation pathways with exogenous application of putrescine. For non-enzymatic antioxidant, it revealed that putrescine was highly effective for sustaining the anthocyanin and flavonoid content in both the varieties under salinity. Whereas, antioxidative enzyme, CAT showed its diminished activity; but activity of GPX and GR were significantly induced under salinity and it was according to the concentration of applied putrescine.