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Abstract

The paper deals with the impact of different concentrations (0.001, 0.01, 0.1 μg/mL) of chromium chloride on heterocyst frequency of Nostoc carneum under laboratory culture condition (2200 lux light intensity, 7.5 pH and 28 ± 2°C temperature). The results showed a statistically significant decline in heterocyst frequency under treated condition with respect to control. In control, heterocyst frequency increased from 3.017 ± 0.273% (4^th day) to 6.026 ± 0.315% (24^th day) while it was 2.137 ± 0.255% and 5.622 ± 0.415% when treated with 0.001 μg/mL CrCl₂ on the similar days respectively. In case of 0.01μg/mL concentration, the percentage of heterocyst frequency on 4th and 24th days was 1.952 ± 0.115 and 3.536 ± 0.211 which declined to be 1.587 ± 0.094% and 1.117 ± 0.218% under the toxic influence of 0.1 μg/mL CrCl₂.

The two way ANOVA revealed a significant variation in heterocyst frequency as an impact of concentration of chromium chloride (F = 30.161, df = 5, 3; p <0.001) and duration of treatment (F = 4.961, df = 5, 3; p <0.05) reflecting the considerable influence of both concentration and duration of heavy metal on heterocyst frequency of N. carneum. The relation between heavy metal toxicity and reduction in heterocyst frequency has been discussed in the paper.

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