Physiological, photochemical, and antioxidant responses of wild and cultivated Carthamus species exposed to nickel toxicity and evaluation of their usage potential in phytoremediation.

Yasemin Ekmekçi,Uğurcan Baran

doi:10.1007/s11356-021-15493-y

Yasemin Ekmekçi, Uğurcan Baran

Open Access

https://doi.org/10.1007/s11356-021-15493-y

Copy DOI

Abstract

The impacts of Ni toxicity on growth behaviors, photochemical, and antioxidant enzymes activities of wild (Carthamus oxyacantha M. Bieb.) and cultivated (Carthamus tinctorius L.) safflower species were investigated in this study. Fourteen-day-old seedlings were treated with excessive Ni levels [control, 0.5, 0.75, and 1.0 mM NiCl2·6H2O] for 7 days. The results of chlorophyll a fluorescence indicated that toxic nickel exposure led to changes in specific, phenomenological energy fluxes and quantum yields in thylakoid membranes, and activities of donor and acceptor sides of photosystems. These changes resulted in a significant decrease in the photosynthetic activities by about 50% in both species, but these negative effects of Ni were not in a level to destroy the functionality of the photosystems. At the same time, toxic Ni affected membrane integrity and the amount of photosynthetic pigments in the antenna and active reaction centers. Additionally, the accumulation of Ni was higher in roots than in stem and leaves for both species. Depending on Ni accumulation, a significant reduction in dry biomass of root by approx. 64.8 and 45.7% and shoot by 41 and 24.7% were observed in wild and cultivated species, respectively. Two species could probably withstand deleterious Ni toxicity with better upregulating own protective defense systems such as antioxidant enzymes and phenolic compounds. Among of them, SOD and POD activities were increased with increasing Ni concentrations. The POD activities of both species were most prominent and consistently increased (approx. 2 folds in roots and 6 folds in leaves) in highly toxic Ni levels and may be protected them from damaging effect of H2O2. When all results are evaluated as a whole, Carthamus species produced similar responses to toxicity and also both species have bioconcentration (BCF) and bioaccumulation factor (BF) > 1 and translocation factor < 1 under Ni toxicity may be regarded a good indication of Ni tolerance. Furthermore, it is possible to use the Carthamus species as phytostabilizers of soils contaminated with nickel, because of their roots accumulating more nickel.

Highlights

Heavy metal pollution is one of the most worldwide threats to the environment organisms
Increasing nickel accumulation of plants leads to alterations in physiological, biochemical and metabolic processes that causes a reduction in growth and biomass production
It has been stated that the inhibition of lateral root formation is a characteristic of Ni toxicity compared to other heavy metals and this response has been explained by the accumulation of nickel in the pericyclic cells (Seregin et al, 2003)

Summary

Introduction

Heavy metal pollution is one of the most worldwide threats to the environment organisms. The concentration of nickel that is required for plant growth is very low, higher Ni concentrations cause toxicity and could lead to several deleterios alterations in plants (Shahzad et al, 2018). Some metals that accumulate in the soil are attached to their organic components and become inaccessible for plants, whereas metal ions can enter the roots . Ni+ 2 uptake and translocation by the plant roots, same as of other metals, take place both passive diffusion and active transport (Seregin and Kozhevnikova, 2006). Nickel uptake and ratio of transport form (active/passive) may vary depending on the species of the plant, oxidation state, pH, concentrations of other metal ions and availability of nickel in the growth medium (Sachan and Lal, 2017; Salinitro et al, 2020). Ni, a divalent cation, may compete with other cations with a similar charge/size ratio such as Fe, Cu, Zn, and Mn, Ni toxicity causes the deficiency of these elements (Shahzad et al, 2018; Hassan et al, 2019)

Methods

Results

Conclusion