TITLE:
Effects of Arbuscular Mycorrhizal Fungi on Metals Uptake, Physiological and Biochemical Response of Medicago Sativa L. with Increasing Zn and Cd Concentrations in Soil
AUTHORS:
Sadia Kanwal, Asma Bano, Riffat Naseem Malik
KEYWORDS:
Zinc, Cadmium, Arbuscular Mycorrhizal Fungi, Alfalfa, Phosphorus, Antioxidant Enzymes
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.6 No.18,
November
24,
2015
ABSTRACT: The effect of mycorrhizal symbiosis on metal accumulation and plant tolerance are not commonly
studied in medicinal plants under metal stress. The objective of this study was to assess the impact
of mycorrhiza on alfalfa plants with the increase of Zn and Cd toxicity. The experiment was conducted
under controlled laboratory conditions. Zinc (Zn) and cadmium (Cd) uptake, some biochemical
and physiological parameters were studied in eight-week-old alfalfa plants in response
to inoculation or not with arbuscular mycorrhizal fungi (AMF) and with the increase of Zn (0, 100,
300, 900 mg·kg-1) and Cd concentrations (0, 100, 300, 600 mg·kg-1) in soil. The results showed
that mycorrhizal (M) plants exhibited tolerance to Zn and Cd up to 300 mg·kg-1 in comparison to
non-mycorrhizal (NM) plants which exhibited a significant growth reduction at the same soil Zn
and Cd level. M inoculation reduced the Zn and Cd accumulation in shoot and showed higher Zn
and Cd contents in roots which showed a different Zn and Cd distribution in AMF associated or
non-associated plants. Mycorrhizal plants increased phosphorus (P) contents at all Zn and Cd
concentrations except the highest (600 and 900 mg·kg-1) leading significant alterations in biochemical
contents such as proline, antioxidant enzymes in leaves and also in nutrients (N, P, K, Cu,
Ni, Fe, Mn). Zn and cadmium toxicity cause to increase the proline content in shoot of NM plants,
however, proline contents are lower in M plants. Results confirmed that AMF protected alfalfa
plants against Zn and Cd toxicity. Mycorrhizal colonization was able to form an efficient symbiosis
with alfalfa plants in moderately contaminated Zn and Cd soils (300 mg·kg-1) and play an important
role in food quality and safety.