Germination ability of barley, wheat, quinoa and oat plants under salinity and heavy metals (Pb, Cd, Zn) stress

Abstract

Introduction: The development of technology in drilling oil and gas wells has created serious
problems for the environment. Drilling fluids have some unwanted compounds such as heavy
metals, hydrocarbons, and salt. The increase in the volume of these activities has caused the
increasing spread of waste in the lands adjacent to the drilling rigs. The discharge of these
compounds in the soil causes damage to the environment. Due to the importance of drilling waste
management to reduce the environmental pollution caused by them, native plants of the region were
selected and compared to the examination of salinity and heavy metal pollution levels, equivalent
to the concentrations of drilling mud, which were prepared and implemented in the laboratory.
Materials & methods: To evaluate germination indicators under salinity stress and heavy metals
(Cr, Cd, Pb), an experiment was conducted in the form of a completely randomized design in the
year 2020 in the laboratory of the Faculty of Agriculture of Islamic Azad University of Isfahan
(Khorasgan). The treatments included the concentration of metals. heavy and salinity at the level
of 0,5,10,15%, four plants (Triticum wheat, Hordeum vulgare barley, Avena sativa oats, and
Chenopodium quinoa) were selected with three replications.
Results: Comparison of the average fresh and dry weight of seedlings, seed germination index, and
germination speed of wheat, barley, quinoa, and oat species showed that with the increase of salinity
and metal stress treatments and their combination treatment, these traits decreased significantly.
According to the research results, the quinoa plant species had the highest fresh and dry weight of
seedlings among plant species. The allometric coefficient in the oat plant species was lower than
the three wheat, barley, and quinoa plant species. 10% salinity treatment followed by 5% salinity
showed the highest allometric coefficient in the quinoa plant with 1.93 and 1.86, respectively, which
increased by 8% and 4%, respectively, compared to the control treatment. The oat plant had the
highest seed germination index under 10 and 15% salinity conditions. The highest germination rate
was related to the wheat plant, followed by the oat plant, and the barley plant had the lowest
germination rate in all experimental treatments. In the conditions of salinity and metals and their
combined treatments (salinity + metals), the quinoa plant had a higher germination percentage than
the other three plant species. It can be concluded that wheat and quinoa plants are more suitable for
the bioassay of heavy metals and salinity than the other two plants.
Conclusion: We believe that heavy metal treatments reduce germination ability, and seedling
growth by inhibiting cell enlargement due to heavy metals. The reduction in seed germination can
be due to the presence of heavy metals on various compounds in the seeds. The results of this study
showed that with the increase in the concentration of lead, cadmium and zinc metals, the percentage
of germination decreased significantly. Wheat plants and then quinoa had higher germination
indices, which can be concluded that probably these plants can absorb fewer metals and have a high
tolerance compared to barley and oat plants.