The data on phytotoxicity of the combined action of chromium and nickel ions on maize hybrids Premiya 190 MV and Euro 401 SV in laboratory vegetation experiments have been analyzed. Plants were grown during 6 days in vegetation vessels at the temperature of 26–27°C on standard Hogland-Snyder’s nutrient medium, with the illumination of 15,000 lux for 16 hours per day and the aeration of nutrient medium. Then chromium and nickel compounds were added into the growth vessels. The effect of the combined action of aqueous solutions of chromium (III) and nickel (II) sulfates was studied in the following variants of the experiment: control (distilled water); 1MPC Ni2++1MPC Cr3+; 10MPC Ni2++ 1MPC Cr3+; 1MPC Ni2++10MPC Cr3+; 10MPC Ni2++10MPC Cr3+ (MPC – maximum permissible concentration). In the experiments, it was assumed that MPC of Cr is 6 mg/l and MPC of Ni is 4 mg/l. Then, after 24 and 72 hours of applying of chromium and nickel solutions, the length of the main root and the height of the aerial part and their weight were measured, and the root index value was calculated. Analysis of the data showed that the inhibitory effect of chromium and nickel ions on the growth of plant of hybrid Premiya 190 MV was 1.4 times less than that for plants of Euro 401 SV hybrid. At 72 hours of plant growth with a minimum concentration of chromium on the background of maximum nickel, the growth inhibition of main root of plants of hybrid Premiya 190 MV was 27%, while at the maximum concentration of chromium on the background of the minimum nickel content – 19.4%. For hybrid Euro 401 SV more effective inhibition of root growth was found: in the variant with the maximum nickel on the background of minimum chromium – by 54.6%, and at the maximum chromium content – by 40%. At the same time, it was found that chromium and nickel ions in minimal concentrations stimulated the main root growth by 16–17 % in Premiya 190 MV, whereas in Euro 401 SV – suppressed by 33%. In general, the similar effects were observed for the production of weight of root system. Most significantly, this effect was revealed in the Euro 401 SV hybrid. Reducing the weight of wet and dry mass of this hybrid plants at the maximum nickel content was 50 and 28%, whereas at the maximum concentration of chromium it was 40 and 20% respectively. The obtained results indicate both the greater negative effect of chromium ions on maize plants and the lower metal tolerance of Euro 401 SV hybrid seedlings compared to the Premiya 190 MV at joint influence of chromium and nickel. The results allow to state that in maize plants at the early stages of their ontogenetic development, there is a greater up to 15% negative effect of nickel ions than chromium on the root and aerial part growth, formation of wet and dry weight. Combined action of chromium and nickel ions shows a greater phytotoxic effect on the root system development than on the aerial parts of plants. This effect is, most likely, due to the functioning of the anatomical, physiological and biochemical barrier mechanisms in the root-leaf system with respect to the excessive translocation of metal ions that cause inhibiting effects.
Testing a Convective-dispersive Model of Two-dimensional Root Growth and Proliferation in a Greenhouse Experiment with Maize Plants
