Soil Chemical Analysis

Human health effects of air pollution

The aim of this review is to assess the mode of action and role of antioxidants as protection from heavy metal stress in roots, mycorrhizal fungi and mycorrhizae. Based on their chemical and physical properties three different molecular mechanisms of heavy metal toxicity can be distinguished: (a) production of reactive oxygen species by autoxidation and Fenton reaction; this reaction is typical for transition metals such as iron or copper, (b) blocking of essential functional groups in biomolecules, this reaction has mainly been reported for non-redox-reactive heavy metals such as cadmium and mercury, (c) displacement of essential metal ions from biomolecules; the latter reaction occurs with different kinds of heavy metals. Transition metals cause oxidative injury in plant tissue, but a literature survey did not provide evidence that this stress could be alleviated by increased levels of antioxidative systems. The reason may be that transition metals initiate hydroxyl radical production, which can not be controlled by antioxidants. Exposure of plants to non-redox reactive metals also resulted in oxidative stress as indicated by lipid peroxidation, H(2)O(2) accumulation, and an oxidative burst. Cadmium and some other metals caused a transient depletion of GSH and an inhibition of antioxidative enzymes, especially of glutathione reductase. Assessment of antioxidative capacities by metabolic modelling suggested that the reported diminution of antioxidants was sufficient to cause H(2)O(2) accumulation. The depletion of GSH is apparently a critical step in cadmium sensitivity since plants with improved capacities for GSH synthesis displayed higher Cd tolerance. Available data suggest that cadmium, when not detoxified rapidly enough, may trigger, via the disturbance of the redox control of the cell, a sequence of reactions leading to growth inhibition, stimulation of secondary metabolism, lignification, and finally cell death. This view is in contrast to the idea that cadmium results in unspecific necrosis. Plants in certain mycorrhizal associations are less sensitive to cadmium stress than non-mycorrhizal plants. Data about antioxidative systems in mycorrhizal fungi in pure culture and in symbiosis are scarce. The present results indicate that mycorrhization stimulated the phenolic defence system in the Paxillus-Pinus mycorrhizal symbiosis. Cadmium-induced changes in mycorrhizal roots were absent or smaller than those in non-mycorrhizal roots. These observations suggest that although changes in rhizospheric conditions were perceived by the root part of the symbiosis, the typical Cd-induced stress responses of phenolics were buffered. It is not known whether mycorrhization protected roots from Cd-induced injury by preventing access of cadmium to sensitive extra- or intracellular sites, or by excreted or intrinsic metal-chelators, or by other defence systems. It is possible that mycorrhizal fungi provide protection via GSH since higher concentrations of this thiol were found in pure cultures of the fungi than in bare roots. The development of stress-tolerant plant-mycorrhizal associations may be a promising new strategy for phytoremediation and soil amelioration measures.

Plant responses to abiotic stresses: heavy metal‐induced oxidative stress and protection by mycorrhization

Reactive oxygen species (ROS) were initially recognized as toxic by-products of aerobic metabolism. In recent years, it has become apparent that ROS plays an important signaling role in plants, controlling processes such as growth, development and especially response to biotic and abiotic environmental stimuli. The major members of the ROS family include free radicals like O2● −, OH● and non-radicals like H2O2 and 1O2. The ROS production in plants is mainly localized in the chloroplast, mitochondria and peroxisomes. There are secondary sites as well like the endoplasmic reticulum, cell membrane, cell wall and the apoplast. The role of the ROS family is that of a double edged sword; while they act as secondary messengers in various key physiological phenomena, they also induce oxidative damages under several environmental stress conditions like salinity, drought, cold, heavy metals, UV irradiation etc., when the delicate balance between ROS production and elimination, necessary for normal cellular homeostasis, is disturbed. The cellular damages are manifested in the form of degradation of biomolecules like pigments, proteins, lipids, carbohydrates and DNA, which ultimately amalgamate in plant cellular death. To ensure survival, plants have developed efficient antioxidant machinery having two arms, (i) enzymatic components like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR); (ii) non-enzymatic antioxidants like ascorbic acid (AA), reduced glutathione (GSH), α-tocopherol, carotenoids, flavonoids and the osmolyte proline. These two components work hand in hand to scavenge ROS. In this review, we emphasize on the different types of ROS, their cellular production sites, their targets, and their scavenging mechanism mediated by both the branches of the antioxidant systems, highlighting the potential role of antioxidant

Reactive oxygen species (ROS) and response of antioxidants as ROS-scavengers during environmental stress in plants

Health risks of heavy metals in contaminated soils and food crops irrigated with wastewater in Beijing, China

Packaging refers to the covering used to protect the product inside. Metals—such as iron, copper, and their alloys, i.e., brass and bronze, have been used for the packaging and storage of goods since ancient times. Unique properties of metals, particularly the ease of fabrication, strength, thermal and electrical conductivities, and ability to hold diverse materials securely in different states, make them an essential packaging material either as such or as composites with materials such as polymers, fibers, plastics, and ceramics. Boxes, cans, cylinders, and foils made from iron, aluminum, tin, copper, etc., are the most common and everyday examples of metal-based packaging; however, specialized packaging requirements, e.g., for electronic parts, composites based on different metals are preferred. After its end use, discarded packaging becomes a major contributor to waste generation. Completely metal-based packages can be recycled; however, this becomes expensive for composites. In such cases, landfilling is the most common disposal method, which may cause adverse impacts on human health through the contamination of groundwater and soil. This calls for effective and better alternate metal waste-management options that can help metal recycling and recovery. In this chapter, we present a brief introduction of metal-based packaging, their various methods of disposal, and recovery and recycling options with particular focus on biotechnological approaches. With the help of different examples and recent developments in the recovery and reuse of waste metals, potential sustainable and cost-effective solutions in managing metallic or metal-based packaging waste are discussed.

Bioprocessing of Metals from Packaging Wastes

Abbreviations : BCF – bioconcentration factor; C i – intercellular CO 2 concentration; E – transpiration rate; eUV-B – elevated UV-B; F 0 – minimal fluorescence; F m – maximum fluorescence; F m /F 0 – electron transport rate through PSII; F v – variable fluorescence; F v /F 0 – the activity of PSII; F v /F m – maximum quantum yield of PSII; g s – stomatal conductance; P N – net photosynthetic rate; RDM – root dry mass; RSR – root-to-shoot ratio; SDM – shoot dry mass; TF – translocation factor. Acknowledgments : The authors are grateful to the Head of the Department of Botany, Banaras Hindu University, for providing all the necessary laboratory facilities. Coordinator, Centre of Advanced Study (CAS), Department of Botany, Department of Science and Technology (DST-FIST), and Interdisciplinary School of Life Sciences (ISLS) are acknowledged for all research facilities. We are thankful to CSIR-CIMAP, Lucknow, India, for providing plantlets of Adhatoda vasica and Sophisticated Analytical Instrumentation Facility, AIIMS, New Delhi for TEM analysis. University Grants Commission (UGC) and Council of Scientific and Industrial Research (CSIR), India are greatly acknowledged for providing financial support in the form of Senior Research Fellowship to Avantika Pandey and Emeritus Scientist Project to Prof. S.B. Agrawal, respectively. The declare that The study was executed to assess individual and interactive effects of elevated ultraviolet-B (eUV-B) radiation and chromium (Cr) on a medicinal plant Adhatoda vasica Nees. The experiment was conducted under field conditions involving control, Cr, eUV-B, and Cr+eUV-B treatments. The results showed that Cr content was the highest in roots as compared to other parts under Cr+eUV-B. Significant reductions in photosynthetic rate, intercellular CO 2 concentration, and stomatal conductance were observed under all treatments with maximum under Cr+eUV-B. Chlorophyll (Chl) fluorescence parameters showed variable responses under Cr and Cr+eUV-B. Chl content showed reductions under all treatments whereas Chl a / b ratio and carotenoids showed increment under eUV-B and reductions under Cr and Cr+eUV-B. The ultrastructure of leaves showed changes in chloroplasts under treatments. Vasicine (medicinally important secondary metabolite) increased under treatments. Our study revealed that A. vasica showed variable responses towards individual and interactive stress of Cr and eUV-B.

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Changes in ultrastructure, photosynthetic abilities, and secondary metabolite due to individual and interactive effects of chromium and ultraviolet-B radiation in Adhatoda vasica

Thwarting Changing Land Use - A Step towards Ganga Rejuvenation

SO2-induced effects and their amelioration by Ca(OH)2 solution in Vigna sinensis plants

Fertilizers are extensively used essentially to meet the food demand of increasing population. Further, they help the plants in alleviating the deleterious effects of UV-B radiation. In this study, we explored this in spinach (Spinacia oleracea L.). S. oleracea plants were grown under ambient and elevated UV-B at different combinations and concentrations of NPK: (i) recommended level of NPK (RNPK); (ii) 1.5 times recommended level of NPK (1.5 × NPK); (iii) 1.25 times recommended level of N plus recommended PK (1.25N+PK); and (iv) 1.25 times recommended level of NPK (1.25 × NPK) to assess the amelioration potential of nutrient combination. Higher availability of NPK provided more protection to plants against oxidative stress as is obvious from reduction in MDA content under elevated UV-B which can be attributed to low oxidative stress due to higher induction of antioxidants. Protection provided to chlorophyll by nitrogen was enhanced by phosphorus and potassium in 1.5 × NPK and 1.25 × NPK compared to RNPK and 1.25 × N+ PK. Maximum increase in PAL activity in plants at 1.5 × NPK did not translate into flavonoid accumulation in same at initial age of observation. Maximum alleviation against UV-B radiation was observed at 1.5 × NPK which can be attributed to better ROS scavenging capacity, more metabolite production and maintaining photochemical efficiency.

Madhoolika Agrawal

Papers

Bioprocessing of Metals from Packaging Wastes

Changes in ultrastructure, photosynthetic abilities, and secondary metabolite due to individual and interactive effects of chromium and ultraviolet-B radiation in Adhatoda vasica

Thwarting Changing Land Use - A Step towards Ganga Rejuvenation

SO2-induced effects and their amelioration by Ca(OH)2 solution in Vigna sinensis plants

Modification in spinach response to UV-B radiation by nutrient management: Pigments, antioxidants and metabolites