Heavy metals (HMs) exists in the environment in both forms as essential and non-essential. These HM ions enter in soil biota from various sources like natural and anthropogenic. Essential HMs such as cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) plays a beneficial role in plant growth and development. At optimum level these beneficial elements improves the plant’s nutritional level and also several mechanisms essential for the normal growth and better yield of plants. The range of their optimality for land plants is varied. Plant uptake heavy metals as a soluble component or solubilized them by root exudates. While their presence in excess become toxic for plants that switches the plant’s ability to uptake and accumulate other nonessential elements. The increased amount of HMs within the plant tissue displays direct and indirect toxic impacts. Such direct effects are the generation of oxidative stress which further aggravates inhibition of cytoplasmic enzymes and damage to cell structures. Although, indirect possession is the substitution of essential nutrients at plant’s cation exchange sites. These ions readily influence role of various enzymes and proteins, arrest metabolism, and reveal phytotoxicity. On account of recent advancements on beneficial HMs ions Co, Cu, Fe, Mn, Mo, Ni, and Zn in soil-plant system, the present paper: overview the sources of HMs in soils and their uptake and transportation mechanism, here we have discussed the role of metal transporters in transporting the essential metal ions from soil to plants. The role played by Co, Cu, Fe, Mn, Mo, Ni, and Zn at both low and high level on the plant growth and development and the mechanism to alleviate metal toxicity at high level have been also discussed. At the end, on concluding the article we have also discussed the future perspective in respect to beneficial HM ions interaction with plant at both levels.

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Influence of High and Low Levels of Plant-Beneficial Heavy Metal Ions on Plant Growth and Development

Heavy metal ions such as cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) are considered essential/beneficial for optimal plant growth, development, and productivity. However, these ions readily impact functions of many enzymes and proteins, halt metabolism, and exhibit phytotoxicity at supra-optimum supply. Nevertheless, the concentrations of these heavy metal ions are increasing in agricultural soils worldwide via both natural and anthropogenic sources that need immediate attention. Considering recent breakthroughs on Co, Cu, Fe, Mn, Mo, Ni, and Zn in soil–plant system, the present paper: (a) overviews the status in soils and their uptake, transport, and significance in plants; (b) critically discusses their elevated level-mediated toxicity to both plant growth/development and cell/genome; (c) briefly cross talks on the significance of potential interactions between previous plant-beneficial heavy metal ions in plants; and (d) highlights so far unexplored aspects in the current context.

Too much is bad--an appraisal of phytotoxicity of elevated plant-beneficial heavy metal ions.

Alleviation of heavy metal toxicity and phytostimulation of Brassica campestris L. by endophytic Mucor sp. MHR-7.

Impact of lead tolerant plant growth promoting rhizobacteria on growth, physiology, antioxidant activities, yield and lead content in sunflower in lead contaminated soil.

Effects of co-administration of methanol leaf extract of Catharanthus roseus on the hypoglycemic activity of metformin and glibenclamide in rats.

A pot culture experiment has been carried out to find the extent of changes occurring in the biochemicals and nutrients of maize plants ( Zea mays L. ) grown under different concentrations of cobalt (50, 100, 150, 200, 250 mg kg -1 soil). The growth and yield parameters such as seedling vigour, number of cobs, number of seeds per plant; photosynthetic pigments viz., chlorophyll â€˜aâ€™, chlorophyll â€˜bâ€™, and total chlorophyll contents; biochemicals like total sugars ( reducing and non reducing), starch, amino acids and protein content and various macro- and micronutrients are determined 90 days after sowing (DAS). All the growth parameters, pigment content, biochemicals and mineral content increase at 50 mg Co kg -1 soil when compared with the control. Further increase in the Co levels (100-200 mg kg -1 soil) has a negative effect on all the above parameters. Â Â  Keywords: Cobalt; Growth; Zea mays ; Biochemicals; Nutrients. Â© 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. Â  Â  DOI: 10.3329/jsr.v1i1.1226 Â

Low Concentration of Cobalt Increases Growth, Biochemical Constituents, Mineral Status and Yield in Zea Mays

6 Abstract: The present study was conducted to find out the antibiogram of different extracts of two varieties of Catharanthus roseus (L.) G. Don. "rosea" and "alba". The plant parts, leaves, stems, roots and flowers were separately tested for their antibiogram by using different solvents (methanol, acetone and ethyl acetate). Among the three solvents used for antibiogram, ethyl acetate extracts of different plant parts were found to induce best antibiogram followed by methanol and acetone extracts. Of the two varieties tested, "rosea" had better antibiogram than "alba". Extracts of all parts of both varieties of C. roseus like root, stem, leaf and flower were found to cause the largest antibiogram towards Bacillus subtilis followed by Klebsiella sp. while least antibiogram was observed against Streptococcus sp. The Staphylococcus aureus was moderately sensitive to different solvent extracts of the plant. The best antibiogram of ethyl acetate could be attributed to hig h solubility of the active compounds of Catharanthus in this solvent compared to other solvents.

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Antibiogram of Catharanthus roseus Extracts

3 influx across the root cell plasma membrane in conferring NE by measuring the short-term NO 2� 3 uptake in selected 10 genotypes. Uptake experiments revealed the presence of two separate nitrate transporter systems mediating high- and low-affinity nitrate uptake. Interestingly, the nitrate uptake by the roots of VL829 is mediated by both high- and low-affinity nitrate transporter systems, while that of HUW234 by only lowaffinity nitrate transporter system. The study suggests that root NO 2� 3 uptake rate may play an important role in conferring N- efficiency of wheat genotypes under N-limiting condition. Also the activities and expression levels of nitrate assimilatory enzymes in N-efficient and N-inefficient wheat genotypes showed that nitrate reductase (NR) and glutamine synthetase (GS) play important roles in N assimilation under low-nitrogen conditions.

Muhammad Iqbal

Papers

Low Concentration of Cobalt Increases Growth, Biochemical Constituents, Mineral Status and Yield in Zea Mays

Antibiogram of Catharanthus roseus Extracts

ORIGINAL ARTICLE Variability of nitrogen uptake and assimilation among N-efficient and N-inefficient wheat (Triticum aestivum L.) genotypes