Ural Federal University: Zinnia and Tobacco Can Grow in Soils Contaminated by Heavy Metals

Zinnia and tobacco adapt to the presence of copper, a heavy metal found in Ural soils. They are able to retain the metal in their cell structures, limiting its transport and effect on the shoots. This was found out by scientists in the course of experiments, the results of which are presented in the PhD thesis of Anastasia Tugbaeva, a Junior Researcher of the Research Laboratory “Biotechnology of Components Maintenance and Restoration of Natural and Transformed Biosystems” of UrFU, and also published in Horticulturae magazine.

The Urals, especially the Sverdlovsk and Chelyabinsk Regions, are characterized by high levels of copper in soils. This problem is very urgent for industrial cities, because the presence of heavy metals in the soil leads to large-scale reduction in arable land, reducing crop yields and plant productivity. In experiments, scientists have shown that plants of the family of asters and nightshades, namely zinnia and tobacco, are able to grow in contaminated soils. They bind heavy metal ions in the cell walls of the root and limit their transport to the above-ground part of the plants.

“These plants are copper eliminators; their root system performs the function of copper accumulation. By the example of zinnia, we have shown for the first time that it can grow on soils contaminated with copper and even go on flowering faster than in clean soils. That is, it can be used for landscaping and will grow well. Tobacco, an important agricultural crop, a useful fertilizer, also adapted to long-term copper exposure in our experiments and grew comparable to control plants, despite the high copper content in the substrate,” says Anastasia Tugbaeva.

The experiments were conducted under conditions close to the real soils of Ekaterinburg and its suburbs. Scientists recreated the conditions of humidity and temperature levels typical of the region and tested the effect of different concentrations of copper sulfate on plant growth and a number of physiological and biochemical characteristics.

“We conducted experiments for 20, 40, and 60 days and used substrates in which copper content could even exceed its content in the soils of Ekaterinburg and its surroundings. Under the influence of copper, the expression of five genes responsible for the synthesis of phenolic compounds and lignin increases in the root and stem of plants. Lignin is one of the components of the plant cell wall which makes it stronger. It is lignin that is the plant’s adaptation mechanism limiting the transfer of metals from the cell wall and the effects of metals on the intracellular structure of the plant,” explains Anastasia Tugbaeva.

The research was supported by the Russian Science Foundation (Project № 22-24-00817). Previously, the laboratory’s staff used genetic modification to breed a tobacco variety capable of cleaning the soil of toxic substances and heavy metals.