NaCl impact on Kosteletzkya pentacarpos seedlings simultaneously exposed to cadmium and zinc toxicities

Abstract

Data regarding NaCl impact on halophyte plant species exposed to a polymetallic contamination remain scarce. Seedlings of the salt marsh species Kosteletzkya pentacarpos were simultaneously exposed to cadmium (10 μM) and zinc (100 μM) in the absence or presence of 50 mM NaCl. Heavy metal exposure reduced plant growth and increased Cd and Zn concentrations in all organs. Cd and Zn accumulation reduced net photosynthesis in relation to stomatal closure, decreased in chlorophyll concentration and alteration in chlorophyll fluorescence-related parameters. Salinity reduced Cd and Zn bioaccumulation and translocation, with a higher impact on Cd than Zn. It mitigated the deleterious impact of heavy metals on photosynthetic parameters. NaCl reduced the heavy metal-induced oxidative stress assessed by malondialdehyde, carbonyl, and HO concentration. Subcellular distribution revealed that Cd mainly accumulated in the cell walls, but NaCl increased it in the cytosol fraction in the leaf and in the metal-rich granule fraction in the roots. It had no impact on Zn subcellular distribution. The additional NaCl contributed to a higher sequestration of Cd on phytochelatins and stimulated glutathione synthesis. The positive impact of NaCl on K. pentacarpos response to polymetallic pollution made this species a promising candidate for revegetation of heavy metal-contaminated salt areas.

Kosteletzkya pentacarpos: A Potential Halophyte Candidate for Phytoremediation in the Meta(loid)s Polluted Saline Soils

“…When considering absorption by Ricinus communis L., the interaction pattern of Cd and Zn showed antagonistic behavior with low concentrations of Cd and Zn (Cd: 1 mg kg −1 soil, Zn: 100 mg kg −1 dry weight soil), but they exhibited a synergistic behavior with high concentrations of the combination of Cd and Zn (Cd: 40 mg kg −1 soil, Zn: 800 mg kg −1 dry weight soil) [23]. In K. pentacarpos, regardless of whether it was exposed to Cd and Zn toxicity for 2 days or for 3 weeks, the excessive Zn had a negative effect on Cd accumulation in the root of plants that were simultaneously exposed to both heavy metals [14,15]. It is well established that Cd and Zn share numerous biochemical properties and that Cd is mainly absorbed by poorly selective Zn transporters (e.g., natural resistance-associated macrophage protein, NRAMP) [24,25].…”

“…It was found that in K. pentacarpos, most Cd was fixed in cell debris that was mainly contained in the cell walls (74%), while for Zn, it was equally accumulated in the cytoplasm (45%) and in the cell debris (50%) [14]. According to literature, cell walls play a vital role in Cd fixation, and this allows Cd to be kept away from the most important metabolic places within the cell [26].…”

“…Recently, K. pentacarpos was proven to have capacities making it able to cope with multiple meta(loid) contamination in salty soil [13][14][15]. Hence, this review summarized the current understanding of the behavior of K. pentacarpos that has been exposed to NaCl and multiple meta(loid) pollutants simultaneously.…”

Polyamines in Halophytes

“…This plant grows in coastal areas contaminated by industrial activity (Lutts and Lefèvre, 2015). Zhou et al (2018a,b) found that salt and heavy metals altered the endogenous PA content, providing protection under these stress conditions. Heavy metals augmented ethylene synthesis, but NaCl depressed it in plants exposed to Cd or the combined treatment (Cd + Zn) but not with Zn.…”

“…The most commonly occurring PAs, found in halophytes, are the diamines putrescine (Put) and cadaverine (Cad), the triamine spermidine (Spd), and the tetramine spermine (Spm) (Shevyakova et al, 2006b; Kuznetsov et al, 2007). These compounds may serve as bioindicators of stress-tolerant lines (Simon-Sarkadi et al, 2007), stabilize biological membranes, regulate ion homeostasis, delay senescence processes (Lutts et al, 2013), regulate membrane transport through a direct interaction with plasma membrane or vacuolar transporters (Pottosin and Shabala, 2014), protect photosynthetic tissues (Malliarakis et al, 2015), regulate the antioxidant system and free-radical machinery (Sudhakar et al, 2015), participate in abiotic stress signaling (Pál et al, 2015), and protect against metal toxicity (Ghabriche et al, 2017; Zhou et al, 2018a,b). Furthermore, PAs also activate genes for stress response and interact with other metabolic pathways by establishing hormonal cross-talk (Pál et al, 2015; Llanes et al, 2018).…”