In a pot experiment, arsenic-hyperaccumulating Pteris cretica cv. Albo-lineata plant ferns were cultivated and exposed to low and high doses of arsenate (20 and 100 mg As/kg, respectively) for six months. Physiological and morphological changes of roots, as well as changes in soil quality of the root zone and bulk soil (water-soluble fraction of elements and activity of soil enzymes), were determined. The results showed that the accumulation of inorganic As, mainly in the form of As3+, did not significantly affect the yield of roots, but caused changes in root morphology (deformation of root cell walls due to lignification) and metabolism (decrease of auxin indole-3-acetic acid and 2-oxoindole-3-acetic acid contents). Although the soil quality results varied according to the As dose, there was a clear difference between the root zone and the bulk soil. The activities of enzymes in the root zone were greater that those in the bulk soil. The results showed a significant influence of the high dose of As (100 mg As/kg), which decreased the activity of arylsulfatase, nitrate reductase, and urease in the root zone, while a decrease in acid phosphatase and nitrate reductase was observed in the bulk soil. The water-soluble fractions of As, organic nitrogen, nitrate nitrogen and organic carbon were significantly affected by the high dose of As.

In a pot experiment, cherry radish (Raphanus sativus var. sativus Pers. ‘Viola’) was cultivated under two levels of As soil contamination—20 and 100 mg/kg. The increasing As content in tubers with increasing soil contamination led to changes in free amino acids (AAs) and phytohormone metabolism and antioxidative metabolites. Changes were mainly observed under conditions of high As contamination (As100). The content of indole-3-acetic acid in tubers varied under different levels of As stress, but As100 contamination led to an increase in its bacterial precursor indole-3-acetamide. A decrease in cis-zeatin-9-riboside-5′-monophosphate content and an increase in jasmonic acid content were found in this treatment. The free AA content in tubers was also reduced. The main free AAs were determined to be transport AAs (glutamate—Glu, aspartate, glutamine—Gln, asparagine) with the main portion being Gln. The Glu/Gln ratio—a significant indicator of primary N assimilation in plants—decreased under the As100 treatment condition. A decrease in antioxidative metabolite content—namely that of ascorbic acid and anthocyanins—was observed in this experiment. A decline in anthocyanin content is related to a decrease in aromatic AA content which is crucial for secondary metabolite production. The changes in tubers caused by As contamination were reflected in anatomical changes in the radish tubers and roots.

Soil contamination with toxic elements affects soil microbiology and causes changes in the interactions between plants and microorganisms. It also significantly affects soil characteristics, plant growth, vegetation type, and agricultural land production (Wahsha et al. 2017, Zeng et al. 2019, Aponte et al. 2020a, Majumder et al. 2022. The accumulation of toxic elements by plants results in entry into the food chain, which then becomes hazardous to human health (Pande et al. 2022).Soil enzymes produced extracellularly by microorganisms are key participants in soil nutrient cycles and functional sustainability. They are sensitive to changes in the soil environment, such as contamination by toxic elements (Wahsha et al. 2017, Nkongolo and Narendrula-Kotha 2020, Cui et al. 2021, Majumder et al. 2022. Due to these characteristics, they can be used as biological indicators for evaluating soil health (Aponte et al. 2020b, Skowrońska et al. 2020.The mineralisation of carbon (C) in the soil is crucial for soil quality, as it increases soil fertility. However, this is influenced by plant root exudation, microbial activities, and soil pH (Yu et al. 2021). The zone of plant roots also influences the activity and