A comparative analysis of heavy metal stress responses in different grain amaranth cultivars

Phytoextraction belongs to the most promising and effective strategies for phytoremediation of soils contaminated with heavy metals (HMs). The aim of this study was to determine the phytoextraction potential of two Slovak grain amaranth cultivars Pribina (Amaranthus cruentus) and Zobor (Amaranthus hypochondriacus × Amaranthus hybridus) compared to a commercial cultivar Plainsman (A. hypochondriacus × A. hybridus). Hydroponic experiment was set up for 14 days of treatment with 200 mg l^-1 Pb(NO₃)₂, 150 mg l^-1 ZnCl₂, and 300 mg l^-1 MnCl₂. The results showed that all cultivars reacted differently to HMs exposure. Based on the morphological analyses, cv. Pribina and cv. Zobor showed a higher level of HM tolerance, especially to manganese. Location of zinc ions was performed by histochemical staining in roots tissues of treated plants. Biochemical analyses showed that lipid peroxidation was more pronounced in cv. Zobor and Plainsman, while guaiacol peroxidase activity was increased in cv. Pribina. Photosynthetic pigments remained mostly unaffected by HM treatment. Significant changes in gene expression were detected in all cultivars, especially for stress-related genes AhDGR2 and Ah24. Translocation of HMs from roots to shoots was not efficient enough to consider grain amaranth as a hyperaccumulator, but a strong phytostabilization potential is presumed for each examined cultivar.