Physiological and molecular mechanisms of metal accumulation in hyperaccumulator plants

Abstract

Most of the heavy metals (HMs), and metals/metalloids are released into the nature either by natural phenomenon or anthropogenic activities. Being sessile organisms, plants are constantly exposed to HMs in the environment. The metal non‐hyperaccumulating plants are susceptible to excess metal concentrations. They tend to sequester metals in their root vacuoles by forming complexes with metal ligands, as a detoxification strategy. In contrast, the metal‐hyperaccumulating plants have adaptive intrinsic regulatory mechanisms to hyperaccumulate or sequester excess amounts of HMs into their above‐ground tissues rather than accumulating them in roots. They have unique abilities to successfully carry out normal physiological functions without showing any visible stress symptoms unlike metal non‐hyperaccumulators. The unique abilities of accumulating excess metals in hyperaccumulators partly owes to constitutive overexpression of metal transporters and ability to quickly translocate HMs from root to shoot. Various metal ligands also play key roles in metal hyperaccumulating plants. These metal hyperaccumulating plants can be used in metal contaminated sites to clean‐up soils. Exploiting the knowledge of natural populations of metal hyperaccumulators complemented with cutting‐edge biotechnological tools can be useful in the future. The present review highlights the recent developments in physiological and molecular mechanisms of metal accumulation of hyperaccumulator plants in the lights of metal ligands and transporters. The contrasting mechanisms of metal accumulation between hyperaccumulators and non‐hyperaccumulators are thoroughly compared. Moreover, uses of different metal hyperaccumulators for phytoremediation purposes are also discussed in detail.

Effect of copper on the photosynthesis and growth of Eichhornia crassipes

“…A recent review (Sytar et al . 2020) found that hyperaccumulator plants can maintain normal physiological functions without showing any visible stress due to the sequestration of heavy metals in root vacuoles and formation of complexes with metal ligands and transporters.…”

“…2021), where they are sequestered in root vacuoles having metal ligands, as a detoxification strategy (Sytar et al . 2020).…”

Morphological Features of Plants on Ash Settling Ponds. Case Study

“…Dense turf covering the anthropogenically transformed surfaces accumulates HMs and absorbs odours, therefore it contributes to a decrease in the amount of hazardous substances and improves quality of the atmosphere [ 17 , 18 ]. Power plants with ash settling ponds are located far from densely populated areas.…”

Chelate-assisted phytoextraction using Brassicaceae plants

“…The heavy metal extraction process is due to two approaches that have currently been used to reach this purpose: the fi rst one results in the exploration of plants with exceptional, natural metal-accumulating capacity, so called hyperaccumulators [22], and the second one is the use of high-biomass crop plants with a chemically enhanced phytoextraction method [6,12,[21][22][23][24][25]. So, the basic properties of those two phytoextraction strategies of metals from soils are illustrated as followed in Table 2.…”