Heavy metal tolerance in common fern species

Abstract

The effects of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) on the growth and uptake of 10 fern species was investigated under a controlled environment in order to evaluate their suitability for phytoremediation. Fern species included Adiantum aethiopicum, Blechnum cartilagineum, Blechnum nudum, Calochlaena dubia, Dennstaedtia davallioides, Doodia aspera, Hypolepis muelleri, Nephrolepis cordifolia, Pellaea falcata and the arsenic (As) hyperaccumulating Pteris vittata. Ferns were exposed to four levels of metals at concentrations of 0, 50, 100 and 500 mg kg–1 for a period of 20 weeks. The response of ferns significantly varied among species and metals. In general, heavy-metal translocation was limited, with metals being absorbed and held in roots, suggesting an exclusion mechanism as part of the ferns’ tolerance to the applied metals. Similar metal-accumulation patterns were observed for all species in that accumulation generally increased with increasing metal treatments; in most cases a sharp increase in metal accumulation was observed between 100 and 500 mg kg–1 treatments, suggesting a breakdown in tolerance mechanisms and unrestricted metal transport. This was corroborated by enhanced visual toxicity symptoms and a reduction in survival rates among ferns when exposed to 500 mg kg–1 metal treatments; and to a lesser extent 100 mg kg–1 metal treatments. Of the species investigated, N. cordifolia and H. muelleri were identified as possible candidates in phytostabilisation of Cu, Pb, Ni or Zn contaminated soils. Similarly, D. davallioides appeared favourable for use in phytostabilisation of Cu and Zn contaminated soils. These species had high survival rates and accumulated high levels of the aforementioned metals relative to other ferns investigated. Ferns belonging to the family Blechnaceae (B. nudum, B. cartilagineum and D. aspera) and C. dubia (Family Dicksoniaceae) were least tolerant to most metals, had a low survival rate and were classified as being unsuitable for phytoremediation purposes. Metal tolerance was also observed in P. vittata when exposed to Cd, Cr and Cu; however, no hyperaccumulation was observed.

Tanacetum vulgare as a Bioindicator of Trace-Metal Contamination: A Study of a Naturally Colonized Open-Pit Lignite Mine

“…Significantly greater accumulation of Cr and Fe occurred in roots than in leaves, suggesting limited mobility and translocation of these metals once absorbed by T. vulgare . Sequestration of metals in roots enables plants to continue uninhibited growth, and it is an important mechanism of metal tolerance (Kachenko et al 2007). These results are in agreement with Page (2002) and Olivares et al (2009), i.e., that Cu, Mn, and Zn are essential plant micronutrients, and their uptake and allocation in plant organs, such as photosynthetic tissues, is high and active.…”

Transfer of metals from crude oil impacted soils to some native wetland species, the Niger-delta, Nigeria: Implications for phytoremediation potentials

“…This is not surprising as this wetland species has been noted to be one of the plants that are ubiquitous in contaminated soils, particularly in mining areas (Kubicka et al, 2015;Samecka-Cymerman et al, 2012). Kachenko et al (2007) also reported that translocation of some metals was limited in P. aquilinum because of absorption and retention in roots, suggesting an exclusion mechanism as part of its tolerance to the metals which is a major factor in phytostabilization. S. nodiflora seems to phytostabilize Pb, Ni and Cr and A. tectorum possesses the potential to stabilize Zn, Pb and Cd.…”

Analysis of Genetic Profiles of Heavy Metal Phytememediator Plants From Gold Mining Areas

“…Namun, ada beberapa jenis tumbuhan yang toleran terhadap logam berat, seperti Nephrolepsis cardifolia, Hypolepsis muelleri dan Pteris vittata. Menurut Kachenko et al (2007), ketiga spesies tumbuhan paku tersebut toleran terhadap logam berat (Cu, Pb, Ni, Zn, Cd dan Cr) dan potensial sebagai phytostabilizer pada tanah yang terkontaminasi logam berat. Jenis tumbuhan lain yang toleran terhadap logam berat adalah tumbuhan dominan yang dapat tumbuh dengan baik di areal bekas tambang yang tercemar limbah logam berat dan berpotensi sebagai fitoremediator seperti Cyperus sp., Lycopodium sp., dan Melastoma sp.…”