In this study, S. cucullata accumulated more than 1000 μg/g
Cu in its tissues, the minimum requirement to be a Cu
hyperaccumulator (Vamerali et al. 2010). Besides, the plants
showed efficient root to shoot translocation between 10 and
15 mg Cu/L exposure, with TF > 1, which is the stipulated
minimum requirement to be a hyperaccumulator (Garbisu and
Alkorta 2001). However, at higher doses (20–30 mg/L), the
plant resorted to an exclusion strategy, whereby, more metal
accumulation was observed in root than in leaf (Rascio and
Navari-Izzo 2011). This advocates that the plant tissues might
have reached their maximum capacity to tolerate, accumulate,
and consequently, phytoextract Cu. Further, Cu extraction coefficient
(EC) for this plant was also >1, and hence, the plant
can be deemed as a Cu hyperaccumulator, with the best efficiency
between 10 and 15 mg Cu/L exposure. The accumulation
of Cu by aquatic plants, both for short and longer durations,
has also been described in Ceratophyllum demersum,
which accumulated 314.6 μg Cu/ g dw. after 24-h exposure to
4mMCu (Devi and Prasad 1998) or in Potamogeton pusillus,
which accumulated 162 μg Cu/ g dw. after 7-days exposure to
0.1 mg/ L Cu (Monferrán et al. 2009).