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The toxic effect of heavy metals on plants is a well known fact [1,2]. Many waste and effluents contain heavy metals in an amount sufficient enough to cause toxicity to crop plants[3]. The accumulation of heavy metals like Nickel, Copper, Cobalt, etc. in soil originates from metal mining and processing and other technologial activities of men have been reported it extensively [4,5]. Hazardous levels of heavy metals change biological equilibrium in soil which in turn unfavourably influences soil fertility, plant development and yield[6,7].

A study of literature indicates that effects of heavy metals on crop plants have received little attention. The information on toxic effect of heavy metals in radish (rafanus sativus L.) an important vegetable crop, is very scanty[8,9].  Therefore it was of interest that I undertook to study dealing with the effect of heavy metals particularly Copper and Nickel on various phases of seedling establishment of Rafanus sativus L. Var. Pusa rashmi.

The literature on Copper and Nickel as a heavy metal has been extensively reviewed.  The quantity of copper in sewage waste water - fed soils was in toxic range (> 22-30 PPM)[11]. Nickel was present in polluted soils[12].

The amount of copper in soil near a nickel refinery has been regarded as high as 2000 PPM[13]. In this paper the toxic and critical levels of Copper and Nickel for radish has been investigated.

From National seed Corporation, New Delhi the certified seeds of Raphanus sativas L. variety Pusa rashmi were procured, then stored in glass stopper bottle. Preliminary selection for uniformity (criteria being the size and colour of seeds), the seeds were surface sterilized with 0.1% HgCl2 for 2 minutes and repeatedly washed with distilled water. Solutions of 10, 50, 100, 200 and 500 PPM concentrations of Copper sulphate and Nickel sulphate individually were prepared in distilled water. The 60-60 seeds were soaked in these different solutions for 2 hours. A control with distilled water was also being run simultaneously. Each treatment was replicated thrice. Then, seeds were washed thoroughly and then transferred into petri plates over wet (with distilled water), filter paper for germination and seedling growth. The experiment was carried out for 10 days under laboratory conditions at 25 degree ± 2 degree C°. The visual emergence of radicals was taken as criteria for germination. The percentage of germination, average root and shoot length and fresh weight of seedlings were recorded and statistically analyzed.

By the treatment of Copper and Nickel, seed germination was severely affected. All the concentrations of Copper and Nickel used except 10 PPM caused a gradual decline in seed germination (Table 1 and 2). A significant reduction occurred in percent germination at 200 and 500 PPM and from 100 PPM of copper onwards, in comparison to control that is 95%. At maximum concentration (that is 500 PPM), the percent germination decreased. The present observations agree with the earlier results where inhibition of seed germination was reported with Copper and Nickel in lentil, chickpea and Pisum sativum.

Table 1 :

Effect of Copper on Seed germination and Seedling growth of Raphanus sativus variety Pusa rashmi

Table 2 :

Effect of Nickel on Seed germination and Seedling growth of Rafanus sativus variety Pusa rashmi

*** highly significant

The growth of shoot was moderately affected by the treatment of metals as a significant reduction was recorded at 200 and 500 PPM of Copper and Nickel. Reduction in shoot length at other concentrations of either metals were not significant. Both copper and Nickel particularly at higher concentrations resulted in adverse effects on root growth. The root growth of radish seedlings decrease significantly after treatment with 100, 200 and 500 PPM of Copper and Nickel in comparison to control. Poor root and shoot growth have been earlier reported in copper amd nickel treated Acer rabrum, Cornus stolonifera, Lonicera tatarica and Pinus resinosa and tomato in sand culture.  

High concentrations of NiCl2 inhibited ear development in wheat plant. The growth of lentil plant in general was retarded by copper treatment. Fresh weight of radish seedlings was also adversely affected by the treatment of metals. Higher concentrations (200 and 500 PPM) of both the metals were significantly effective in reducing the fresh weight of seedlings. 

Significant reduction in fresh weight of root and shoot of chickpea treated with 400 PPM of Nickel was earlier observed.. Reduction in fresh weight of pigeon pea maybe due to high amount of heavy metals especially copper and zinc which damage the plant cells so that plant cannot grow in high concentrations³. 

1. Khan, M.R., Singh, S.K. and Khan, M.W., 1987. Effect of Nickel on growth of lentil plants. IAWPC, Technical annual, 14. 57-60 2. Satake, M., Mido, Y., Sethi, M.S., Iqbal, S.A., Yasuhisa, H. and Taguchi, S. 1997. Environmental Toxicology. Discovery Publishing House, New Delhi. 278 3. Singh, P. and Singh, V.P. 1997. Phytotoxic effect of city waste on growth and chlorophyll content in pigeon pea. J. Environ. Pollut. 4(4). 265-269 4. Davies, B.E., 1983. Heavy metal contamination from base metal mining and smelting : implications for man and his environment. In Thornton, I. (Ed.) Applied Environment Geochemistry Academic, London. 425-462 5. Singh, J. and Kansal, B.D. 1983. Accumulation of heavy metals in soils receiving municipal waste water and effect of soil properties on the availability. In : Heavy metals in the environment. CPC., Consultants Ltd., Edinburg. U.K.I. 409-412. 6. Mitchell, R. (ed.) 1992. Environmental Microbiology, Wiley-Liss, Inc., New york. 411 7. Maliszewska, W, Dec, S., Wierzbicka, H. and Wozniakowaska, A. 1985. The influence of various heavy metal compounds on the development and activity of soil microorganisms. Environ. Pollut. 37. 195-215 8. Davis, B.E., Lear, J.M., Lewis, N.J. 1987. Plant availablility of heavy metals in soils. In Coughtret, P.J., Martin, M.H., Usworth (ed.). Pollutant transport and Fate in Ecosystems. Blackwell, Oxford. 267-275 9. Khan, D.H. and Frankland, B. 1983. Effect of cadmium and lead on radish plants with particular reference to movement of metals through soil profile and plant. Plant and Soil, 70. 335-345 10. Singh, S.N. 1981. Physiology of the Heavy Metal Pollutant – Nickel, M. Phil. dissertation, Meerut University, India. 11. Hundal, K.S. and Sandhu, S.S. 1990. Effect of sewage water on soil properties and Heavy metal accumulation. India J. Ecol. 17. (1) 42-47 12. Kumar, Rabi, 1992. The extent of Nickel build up in polluted soil and evaluation of its toxicity to plants. M.Sc. Thesis. Punjab Agric. Univ. Ludhiana. 13. Bisessar, S., Rinne, R.J. and Potter, J.W. 1983. Effect of heavy metals and Meloidogyne hapla on celery grown on organic soil near Nickel refinery. PI. Dis. 67. (1): 11-14.