Cyperus rotundus: a safe forage or hyper phytostabilizer species in copper contaminated soils

Abstract

This study was carried out to evaluate Cu uptake, mobility, and accumulation in Cyperus rotundus and define the physiological strategy it employs under copper stress conditions. The experiment was performed at concentration levels from 12, 100, 150, 200, 250, and 300 mg Cu/kg in pod soil. The metal concentrations in roots, tubers, and root organs and the translocation factor (TF), total soluble sugars (TSS), and biomass production were evaluated. The results showed that the changes in TF and Cu concentrations had good fitness (p value < 0.01; R 2 > 0.87) with the quadratic models. These models have indicated C. rotundus has limited Cu translocation from the roots to the shoots (0.009 < TF < 0.05). The results also showed that TSS significantly (p value < 0.05) increased under Cu stress and changes in both the shoot and tuber tissues had good fitness with the quadratic model (R 2 > 0.98). In summary, C. rotundus is a hyper tolerant plant with a high ability to take up Cu from the soil, accumulate it in its underground tissues and prevent Cu translocate in above ground tissues. Therefore C. rotundus can be considered as a hyper phytostabilizer with the ability to hold Cu concentration in its shoot at a lower level than the maximum allowable concentrations in animal food and so can be recommend as safe forage in the copper contaminated environment. Novelty statement This paper reported for the first that Cyperus rotundus can be hyper Phytostabilizer if tubers and roots are considered as an unharvestable part. Cyperus rotundus can be suggested as a safe palatable plant due to the following three indices: (1) the maximum Cu concentration observed in the shoots is less than the maximum authorized concentration (MAC) in animal food, (2) the Translocation Factor of Cu (TF < 0.05) is very low, and (3) the physiological strategy of “excluders sensu Baker” used for copper phytostabilizing prevent more translocation and accumulation of Cu under more sever contaminated conditions, so this species could be used for grazing and forage production in copper contaminated environments. Safety forage assessment under a metal-contaminated environment using the three main indices described above is a novel idea.