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The hazardous effect of Copper and Nickel individually was assessed on seed germination and seedling growth of Raphanus sativus variety Pusa Rashmi. It was noticed that both the heavy metals badly affected the seed germination and seedling growth at higher concentrations (200 PPM and 500 PPM). Copper was more toxic than Nickel to both seed germination and seedling growth. All the concentrations of Copper and Nickel used except 10 PPM onward showed a gradual decline in seed germination and seedling growth of Raphanus sativus variety Pusha rashmi.

This research work is carried out to study the effect of Copper and Nickel individually on seed germination and seedling growth of Raphanus sativus variety Pusa rashmi.

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. 

It is thus evident from the results that inhibition in root length of radish seedlings under the effect of heavy metals was higher than hypocotyl, and also that copper is comparatively more toxic than nickel to plant growth. The results indicate that shoot length is moderately affected by Copper and Nickel treatment. The adverse effect of copper on seedling growth were due to inhibition of root elongation. Copper has been found more inhibitory for soil microbes⁷. High concentrations of Nickel beside suppressing protein synthesis and activity of various enzymes also causes iron competition in culture medium. Diminutive effects of copper, nickel and cobalt have been observed on growth characters, biomass, yield, etc. of celery, tomato and lentil plants both in ambient and artificial treatment conditions. The seedling root length of Raphanus sativus variety Pusa rashmi being more susceptible to the effect of heavy metals (Copper and Nickel) as observed may be used as a bio assay for toxicity and tolerance studies.

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