Synergic effect of salinity and zinc stress on growth and photosynthetic responses of the cordgrass, Spartina densiflora

Abstract

Spartina densiflora is a C4 halophytic species that has proved to have a high invasive potential which derives from its physiological plasticity to environmental factors, such as salinity. It is found in coastal marshes of south-west Spain, growing over sediments with between 1 mmol l−1 and 70 mmol l−1 zinc. A glasshouse experiment was designed to investigate the synergic effect of zinc from 0 mmol l−1 to 60 mmol l−1 at 0, 1, and 3% NaCl on the growth and the photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters and gas exchange, and its recovery after removing zinc. Antioxidant enzyme activities and total zinc, sodium, calcium, iron, magnesium, manganese, phosphorus, potassium, and nitrogen concentrations were also determined. Spartina densiflora showed the highest growth at 1 mmol l−1 zinc and 1% NaCl after 90 d of treatment; this enhanced growth was supported by the measurements of net photosynthetic rate (A). Furthermore, there was a stimulatory effect of salinity on accumulation of zinc in tillers of this species. Zinc concentrations >1 mmol l−1 reduced growth of S. densiflora, regardless of salinity treatments. This declining growth may be attributed to a decrease in A caused by diffusional limitation of photosynthesis, owing to the modification of the potassium/calcium ratio. Also, zinc and salinity had a marked overall effect on the photochemical (photosystem II) apparatus, partially mediated by the accumulation of H2O2 and subsequent oxidative damage. However, salinity favoured the recovery of the photosynthetic apparatus to the toxic action of zinc, and enhanced the nutrient uptake.

Growth, chlorophyll fluorescence and mineral nutrition in the halophyte Tamarix gallica cultivated in combined stress conditions: Arsenic and NaCl

“…This might be caused by the formation of complexes between chloride and metals [74]. Redondo-Gomez et al [75] reported that salinity was promoted trace metals tolerance, through excretion metals in salt crystals liberated by salt glands in order to reduce its negative effects on cell metabolism. Bankaji et al [4] observed the same behaviour in two halophytic species Atriplex halimus and Suaeda fruticosa, which suggests an addition of NaCl to the irrigation solution can significantly reduce the endogenous Cd 2+ and Cu 2+ concentration in different tissues.…”

Spartina alterniflora with high tolerance to salt stress changes vegetation pattern by outcompeting native species

“…Therefore, S. alterniflora suffers relatively little damage from high salinity. Specifically, some scholars have reported that the photosynthesis of cordgrass does not significantly change in the salinity range of 0-510 mM (Mateos-Naranjo et al 2010, Redondo-Go'mez et al 2011. Moreover, S. alterniflora can efficiently absorb water at high salinity because it's osmotic potential will increase with increasing salinity (Vasquez et al 2006).…”

Salinity alleviates zinc toxicity in the saltmarsh zinc-accumulator Juncus acutus

“…These studies however, did not take account of the potential interaction of Zn with other important factors characteristic of marshes ecosystems, particularly salinity. It has been demonstrated that the accumulation of sodium in another halophyte, Spartina densiflora, can mitigate its responses to Zn-induced stress (Redondo-Gómez et al, 2011). Hence knowledge of the extent to which salinity might modulate the physiological responses of J. acutus to excess Zn is necessary for a realistic assessment of its metal toxicity thresholds and its potential for the remediation of zinc-polluted saltmarshes.…”