Exogenous 24-Epibrassinolide alleviates oxidative damage from copper stress in grape (Vitis vinifera L.) cuttings.

Ecological potential of Epilobium dodonaei Vill. for restoration of metalliferous mine wastes

Traditional herbal plant-based medicines were characterized by having good amount of antioxidants. But due to the rapid industrialization and urbanization, addition of heavy metal accumulation in soil-plant affected the growth of plants including medicinal plants. Under metal stress, both the antioxidant enzymes and phytochemicals constituting nonenzymatic components coordinately work to encounter abiotic stresses. Antioxidant enzymes such as polyphenol oxidase (PPO), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), phenylalanine ammonia-lyase (PAL), ascorbate peroxidase (APX), lipoxygenase (LOX), glutathione reductase (GR), glutathione peroxidase (GPX), guaiacol peroxidase (GPO), glutathione-S-transferase (GST), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) are altered in stressed conditions which leads to the changes in free radical content. In addition, different components of nonenzymatic defense system such as glycine betaine (GB), proline, glutathione (GSH), ascorbic acid (AsA), tocopherols, carotenoids, flavonoids, and phenolic compounds also play crucial role at cellular level. Almost every type of stress leads to the overproduction of reactive oxygen species (ROS). They are vigorously produced in response to most abiotic stresses and used as signaling molecules by cells. As they are highly reactive species, a balance between their production and detoxification must be ensured. By transformation of plants in which activity of single antioxidant enzyme is overexpressed, it is possible to confer a degree of tolerance to stress. The success of plant transformation has allowed the scientists to confer greater stress tolerance in plants by improvements in the antioxidative defense system.

Effects of Different Metal Stresses on the Antioxidant Defense Systems of Medicinal Plants

An attempt was made to explore the effect of copper sulphate treatment on growth, photosynthesis, osmolytes and antioxidants in 15 days old seedlings of C. cajan (Pigeonpea). C. cajan seedlings were grown in 0, 1, 5 and 10 mM concentrations of copper sulphate in petriplates lined with Whatman filter paper for 15 days. Root length and shoot length was decreased in a dose dependent manner with highest decrease of 82.80 and 45.92% in 10 mM Cu stress. Photosynthetic efficiency (qP, qN and Y) was decreased in a dose dependent manner whereas NPQ was increased in 1 and 5 mM and decreased in 10 mM Cu. Photosynthetic pigments viz total chlorophyll and carotenoids were increased in low concentrations and decreased in high concentrations of Cu. Osmolytes such as proline, glycine betaine and sugars were found to be increased in a dose dependent manner. Similarly antioxidants such as superoxide dismutase and catalase increased to 129.17 and 169.7%, respectively under Cu stress. Vitamin C and vitamin E was also increased in different concentrations of Cu to a significant level. It can be concluded from the present study that C. cajan can tolerate Cu stress up to 5 mM by adjusting the proportion of proline, glycine betaine, sugars and vitamins along with increasing the activity of some of the antioxidant enzymes.

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Consequences of copper treatment on pigeon pea photosynthesis, osmolytes and antioxidants defense

Increased dependence on thermal power has resulted in a significant increase in the generation of fly ash (FA), which exacerbates environmental pollution. In order to mitigate this source of pollution, we propose covering FA dumps with a layer of planted vegetation. Due to varying degrees of tolerance and their sessile nature, plants are themselves susceptible to stress from pollution. This suggests that an investigation to assess the role of wild growing plants for management of FA dumps, where selected wild plants could be grown to mitigate consequences of FA. The present study assesses oxidative damage and the foliar concentration of metals in Withania somnifera growing wild at the Badarpur Thermal Power Plant (BTPP) compared to those growing at a control site. Plants growing at the BTPP showed significantly higher foliar concentrations of Pb, Mn, and Fe, and low concentrations of Ni and Cd. The plants at the BTPP site showed signs of oxidative stress as indicated by enhanced levels of malondialdehyde and electrolyte leakage from cells. The CO2 assimilation rate, net photosynthetic rate, rate of transpiration, stomatal conductance decrease, while water use efficiency, and air pollution tolerance index increase. Among air pollution tolerance index parameters, relative water content showed a significant increase with FA pollution stress at the BTPP. A significant decrease was observed in leaf morphology single leaf area, leaf length, and leaf width and biochemical parameters (Chlorophyll a, Chlorophyll b, total chlorophyll, and carotenoids. Moreover, FA pollution stress induces oxidative stress in W. somnifera through a significant and enhanced production of reactive oxygen species (ROS). According to our observations, the ability of W. somnifera to effectively coordinate superoxide dismutase, ascorbate peroxidase, and glutathione reductase activities involved in the scavenging of ROS along with the enhanced increment of nonenzyme activities (total ascorbic acid, proline, and oxidized glutathione) could be related to FA stress tolerance in W. somnifera.

Foliar Concentrations of Selected Elements, Assessment of Oxidative Stress Markers and Role of Antioxidant Defense System is Associated with Fly Ash Stress Tolerance in Withania somnifera

The effects of Cu+2 stress (0, 10, 20, 50, 100 and 200 mM as CuSO4.5H2O) on growth and biochemical parameters of Withania somnifera L.Dunal, grown in a field pot experiment were studied. Increasing Cu+2 concentrations led to decreased stem length, root elongation and leaf area. Copper (Cu+2 ) stress decreased chlorophyll and carotenoids content in leaves and stems as compared to controls; this was more pronounced in leaves than in stems. Lipid peroxidation, in terms of malondialdehyde (MDA) content increased. Lipid peroxidation increased significantly with elevation in Cu+2 concentrations and was highest in roots followed by leaves and stems at 200 mM. Leakage of electrolytes measured in terms of membrane stability index (MSI), which showed a negative correlation with increasing Cu+2 levels. The MSI was lowest in 200 mM Cu+2 treated plants. The phenol content of leaves, stems and roots peaked at 50 mM Cu+2 treatment and thereafter declined. These results indicate that Cu+ 2 stress negatively impacted nearly all the parameters assayed; particularly in the roots. It is being reported for the first time that stress resistance in W.somnifera as observed by increase in total phenol content at low Cu+2 levels possibly to combat increased ROS generation.

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Swati P

Papers

Response of leaves, stems and roots of withania somnifera to copper stress