Accumulation of heavy metals in sunflower seedlings under the influence of cadmium stress

Abstract

Steady trend of recent decades is the rapid growth of soil pollution by heavy metals. Metals that do not play a significant role in plant life are particularly dangerous, but they can accumulate in plants and migrate along the food chain. Cadmium is one of such elements, its half-life from the human body is more than 50 years. For breeding programs aimed at creating varieties with low levels of cadmium accumulation, it is important to understand the role of genotype in the processes of metal intake to different parts of plants. An experiment was carried out to study the growth and absorption of trace metallic elements (TMEs) in Sunflower (Helianthus annuus L.) seedlings under Cd stress. The research was done on selection samples of sunflower selected by the method of vegetation evaluation in Sumy NAU in 2018. According to the evaluation results, line 62\3 was characterized by low, and line JB231AC – high level of resistance to cadmium accumulation. In 2020, the seeds of the samples were reseeded at the Henan Institute of Science and Technology. Sunflower seedlings (20-day-old) grown in plastic containers with Hogland’s solution were investigated. From uniformly and well-developed plants were formed 4 samples which were for 7 days in a solution of CdCl2 * 2.5 H2 0 with a concentration of 0; 25; 50 and 100 μM. Ashing of the samples was performed in nitric acid. Determination of metal content was performed on an atomic adsorption spectrophotometer. In all samples there was a steady trend to decrease plant height and total seedling weight with increasing cadmium concentration. In the case of dried parts of plants, statistically significant, leveling the difference between the samples, the effect of cadmium was detected at a concentration of 50 μm or more for the dry matter of roots and at a concentration of 100 μm for the mass of the aboveground part. It was found that the threshold concentration that provided a significant difference between the cadmium content in the roots and stems was 100 μm. Compared to sample JB231AC, sample 64\2 had a higher cadmium content in the roots by 23 % and 12 % in the aboveground part. With respect to Li, Ni, and Sr, a significant difference between the samples was mostly observed at a concentration of 25 and 50 μM. The accumulation concentration of lithium (Li) and nickel (Ni) in high Cd variety 62\3 was lower than that in low Cd variety JB231AC. The Li and strontium (Sr) concentration in the root were similar to that in the aboveground part under Cd stress, while Ni accumulated in root of JB231AC in slightly higher concentrations than that in aboveground part. The presence of an inverse relationship between the concentration of cadmium and the concentrations of lithium and nickel may indicate both the genotypic features of their transport and the presence of antagonism between the accumulation of these metals. However, this statement requires further research.