Heavy Metal Effects on Biodiversity and Stress Responses of Plants Inhabiting Contaminated Soil in Khulais, Saudi Arabia

Abstract

Accumulation of heavy metals in soil is becoming an increasingly serious eco-environmental problem. Thus, investigating how plants mitigate heavy metal toxicity is necessary to reduce the associated risks. Here, we aimed to assess the bioremediation and stress defense strategies of tolerant plant species grown under complex heavy metals contamination. To this end, a field study was conducted on the vegetation cover of sites with different soil pollution levels. Forty-two plant species that belong to 38 genera and 21 families were identified. The pollution had a significant impact on plant richness in the polluted sites. Out of several screened plants, Amaranthus retroflexus L. was selected because of its high relative density (16.7) and a high frequency (100%) in the most polluted sites. The selected species showed a high biological concentration factor (BCF) and low translocation factor (TF) for Cu, As and Ni. To control the heavy metal-induced oxidative damage, A. retroflexus invested in detoxification (metallothionein and phytochelatins, glutathione and glutathione-S-transferase (GST). At the organ level, oxidase damage (H2O2, lipid and protein peroxidation) was observed, particularly in the roots. To mitigate heavy metal oxidative stress, antioxidant mechanisms (e.g., tocopherols, glutathione, peroxidases, catalase, peroxide dismutase and ASC-GSH cycle) were upregulated, mainly in the roots. Overall, our results suggested the potentiality of A. retroflexus as a promising bioremediatory and stress-tolerant plant at the same time; moreover, defense and detoxification mechanisms were uncovered.

Evaluating the ecological consequences of heavy metal contamination in soil induced by spent engine oil and palm oil mill effluents for sustainable development

“…Secondly, the potential for bioaccumulation of heavy metals in plant and animal tissues raises concerns about their entry into the food chain, posing risks to human health. Thirdly, the impact of heavy metal contamination on biodiversity, soil fertility, and overall ecosystem functioning has broader implications for sustainable development [9][10][11][12].…”

Antioxidant activities in relation to the transport of heavy metals from the soil to different parts of Betula pendula (Roth.)

“…In the assessment of heavy metal interactions, useful tools for determining both soil contamination and also the bioavailability of metals for the plant as well as transport and accumulation are a series of quite extensively developed and discussed indicators [ 1 , 5 , 13 , 14 ]. Among the wide range of indicators, one can choose those that fully characterise the geochemical cycle, indicating the most important elements of it prone to accumulation [ 14 ].…”

“…The increased content of toxic substances in plant tissues triggers a cascade of reactions, including the formation of an excessive amount of reactive oxygen species. Plants have developed some efficient mechanisms to scavenge ROS, including enzymatic and non-enzymatic ones [ 13 , 25 , 26 ]. Among these mechanisms are antioxidants.…”

Physiological dynamics as indicators of plant response to manganese binary effect

“…Recently, heavy metal pollution in soil has become increasingly serious due to ore smelting and the excessive use of chemical fertilizers ( Ali et al., 2013b ). Pollution poses challenges to plant growth, agricultural production, and ecosystem health and even threatens human health and food safety ( Alsherif et al., 2022 ; Sarker et al., 2022 ; Wen et al., 2022 ). Heavy metals in soil persist for a long time because of their poor mobility and resistance to biodegradation.…”