The effect of the combined action of nickel and copper ions on the initial stages of ontogenesis of Alisma plantago-aquatica

Abstract

Surface water pollution has a complex multicomponent nature, due to a combination of various heavy metals that have a synergistic or antagonistic effect on various physiological parameters. Under model conditions, the combined effect of several heavy metals on aquatic plants was studied in terms of their toxicity, taking into account the nature of the interaction. In laboratory conditions, we studied the effect of nickel and copper ions and their mixtures in different concentrations on seed germination, growth and development of seedlings of the coastal-aquatic plant Alisma plantago-aquatica L. At the end of the experiment, seed germination, inhibition coefficient, morphometric indicators of seedlings and tolerance index were determined. Alisma seeds are highly resistant to nickel and copper chlorides and their mixtures. The toxicity limit for seed germination at 1–500 mg/L was not detected, although the inhibition coefficient in all variants of the experiment increased. A greater toxic effect of copper ions was noted compared to nickel ions. With the joint action of two metals on seed germination, a change in the nature of the effect from an independent action at low concentrations to antagonism at high concentrations was revealed. The growth and development of seedlings was observed at 1–100 mg/L. The main inhibitory effect of heavy metals was on the length of the main root, the first true leaf, and the number of adventitious roots. Necrosis of the root system and hypocotyl, a weakening of the differentiation of the site of transition of the hypocotyl to the cotyledon, a change in the shape of the cotyledon, the colour intensity and turgor of the cotyledon and leaves were noted. The tolerance index showed that resistance at a level above 50% to the action of nickel, copper and their mixture was maintained at 1 mg/L. In the case of the development of hypocotyl and cotyledon, copper was more toxic than nickel; nickel had a greater inhibitory effect on leaves. Under the action of the heavy metal mixture on the growth and development of seedlings, the independent action at low concentrations changed to antagonistic at high concentrations, which is probably due to competition in a number of indicators between nickel and copper.