Abstract
The role of mangroves as a biogeochemical buffer for heavy metal pollutants in coastal wetlands has been demonstrated, but knowledge gaps still exist on the tolerant capacity of mangroves to aluminum (Al). This study assessed the growth and physiological response of viviparous mangroves Kandelia obovata and Bruguiera sexangula to Al stress. The two mangrove seedlings were treated with AlCl3 at concentrations of 0 (as control) to 100 mmol L−1, and the impact of Al on their growth and antioxidant parameters were determined. Additionally, the accumulation and translocation of metal elements were estimated in B. sexangula seedlings under relative long-term Al stress. K. obovata appeared to survive with a tolerance potential of 10 mmol L−1 AlCl3, whereas B. sexangula had a higher tolerant ability of 50 mmol L−1 AlCl3. Both root elongation and seedling growth were inhibited by Al stress. The exposure to 25–100 mmol L−1 AlCl3 induced increases in membrane lipid peroxidation and osmoprotectant molecule (proline) in mangrove seedlings. Both mangrove seedlings revealed significant changes in antioxidant enzyme activities that were attributed to Al stress-induced oxidative damages. The activities of superoxide dismutase, catalase, peroxidase, and/or ascorbate peroxidase were differently impacted by the treatment time (7 days for short term versus 60 days for long term) and AlCl3 concentrations in K. obovata and B. sexangula seedlings. For B. sexangula seedlings, Al accumulation was in an order root > leaf > stem, whereas the translocation of metal elements in the aboveground tissues (leaf and stem) was differently impacted by Al stress. In conclusion, this study provides insights into different Al-tolerant abilities operated in two mangrove species that are widespread in coastal wetlands of China.
Highlights
Anthropogenic activity has resulted in increases in the carbon dioxide (CO2) release and the global atmospheric CO2 concentration in the past two centuries (Siegenthaler et al 2005; Le Quéré et al 2015; NOAA/ESRL 2019)
K. obovata and B. sexangula are both salt exclusion mangrove species belonging to Rhizophoraceae Pers., which is associated with heavy metal regulation (MacFarlane et al 2007; Zhang et al Fig. 7 The translocation factor (TF) of Al (a), Na (b), K (c), Mg (d), Ca (e), Mn (f), Fe (g), Cu (h), and Zn (i) in B
This work demonstrates that the mangroves K. obovata and B. sexangula can adapt to high levels of AlCl3 in acid conditions, with the tolerance to Al toxicity reaching a maximum concentration of 10 and 50 mmol L−1, respectively
Summary
Anthropogenic activity has resulted in increases in the carbon dioxide (CO2) release and the global atmospheric CO2 concentration in the past two centuries (Siegenthaler et al 2005; Le Quéré et al 2015; NOAA/ESRL 2019). As a special type of tropical forests growing in tidal flooded coastal areas, mangrove forests are salt-tolerant and submerge-resistant (Ball et al 1997; Chen and Wang 2017), and their unique distribution at the transition zone between terrestrial and aquatic environments makes them impacted by costal acidification (Sippo et al 2016). Because the amounts of dissolved aluminum cations (Al3+) are significantly enhanced and released compared with other heavy metals, high concentrations of mobile aluminum (Al) has become a potential pressure for plants (Cook et al 2000; Pred and Cox 2002; Ramos e Silva et al 2006). Previous studies have demonstrated that mangrove seedlings are able to grow under very high concentrations of heavy metals Previous studies have demonstrated that mangrove seedlings are able to grow under very high concentrations of heavy metals (Walsh et al 1979; MacFarlane and Burchett 2002; Miao et al 2007; Ravikumar et al 2007; Dai et al. Vol.:(0123456789)
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