Cadmium effect on the association of jackbean (Canavalia ensiformis) and arbuscular mycorrhizal fungi

Abstract

The effect of cadmium (Cd) on mycorrhizal association and on shoot and root Cd concentration was investigated in jackbean plants under hydroponic conditions. The treatments consisted of the inoculation of three different species of arbuscular mycorrhizal fungi (AMF), Glomus etunicatum, G. intraradices and G. macrocarpum, and a non-inoculated control, two Cd (0 and 5 µmol L -1 ) and two P (1 and 10 mg L -1 ) levels in the nutrient solution. Mycorrhizal colonization, length of AMF extraradical mycelium, guaiacol peroxidase activity in roots, plant growth and root and shoot Cd and P concentrations were determined. Mycorrhizal status did not promote jackbean growth but in most of the cases mycorrhization increased root and shoot Cd concentrations. Cd ions were accumulated mainly in roots and only small amounts were translocated to the shoot. Cd addition did not affect root colonization by AMF but the AM extraradical mycelium (ERM) was sensitive to the added Cd. ERM length was reduced by 25% in the presence of Cd. This reduction was more pronounced under conditions of low P concentration. Also at this P concentration, Cd addition decreased guaiacol peroxidase activity in non-mycorrhizal roots and in roots colonized by G. macrocarpum. However, mycorrhizal roots maintained lower values of peroxidase activity. G. etunicatum showed the best performance when associated to jackbean plants and it could be a promising association for phytoremediation of Cdcontaminated soil. Key words: peroxidase, Cd accumulation, extraradical mycelium, phytoremediation, hydroponics EFEITO DO CADMIO NA ASSOCIAÇÃO DE FEIJÃO DE PORCO (Canavalia ensiformis) E FUNGOS MICORRÍZICOS ARBUSCULARESRESUMO: O efeito do cádmio na associação micorrízica e no teor e acúmulo de Cd na raiz e parte aérea de feijão de porco foi avaliado em condição de hidroponia. Os tratamentos consistiram da inoculação ou não de três espécies de fungos micorrízicos arbusculares (FMAs), Glomus etunicatum, G. intraradices e G. macrocarpum, e uma testemunha (ausência de FMA), duas concentrações de Cd ( 0 e 5 µmol L -1 ) e de P (1 e 10 mg L -1 ) na solução nutritiva. Foram determinados a colonização micorrízica, o comprimento do micélio extraradical, atividade da peroxidase nas raízes, crescimento das plantas e teor e acúmulo de Cd e P na raiz e na parte aérea das plantas. A associação micorrízica não promoveu crescimento das plantas mas aumentou a concentração foliar e radicular de Cd. O metal pesado foi acumulado principalmente nas raízes e somente uma pequena quantidade foi translocada para a parte aérea. A colonização micorrízica não foi influenciada pelo Cd adicionado, mas o micélio extrarradicular mostrou-se sensível ao metal, tendo sido reduzido em 25%, principalmente na menor concentração de P adicionado. Nesta mesma concentração de P, a adição de Cd reduziu a atividade da peroxidase nas raízes das plantas não colonizadas e nas colonizadas por G. macrocarpum. Entretanto, as raízes micorrizadas mostraram valores menores de atividade da enzima. Melhor desempenho da...

Phosphorus availability changes the internal and external endomycorrhizal colonization and affects symbiotic effectivenes

“…As a result, less metabolically active mycorrhizal mycelium would be formed. The amount of TEM found in this experiment was comparable to previous findings (Sylvia, 1988;Cardoso-Filho et al, 1999;Andrade et al, 2005;Nogueira & Cardoso, 2006). Other evaluations for hyphal lengths of filamentous fungi under natural conditions, however, reached even much higher values, up to more than 100 m cm -3 of soil (Miller et al, 1995).…”

“…At the highest P level, the amounts did not differ from those of the AMF-free control. Similar decrease in TEM was observed previously in response to increasing P (Andrade et al, 2005), but in some cases there were increases in TEM with P addition in the substrate (Cardoso-Filho et al, 1999;Neumann & George, 2005) or no change (Nogueira & Cardoso, 2006). However, soil type and host plant were different in those experiments.…”

“…The amount of TEM from G. intraradices was similar in previous work under low P condition, in which other Glomus sp. species produced less TEM (Andrade et al, 2005). When P levels increased, G. rosea intrinsically continued producing less TEM than G. intraradices.…”

“…Andrade et al (2005) observed that increasing P levels reduced the mycorrhizal external hyphae. Nevertheless, several authors found exactly the opposite (Cardoso-Filho et al, 1999;Melloni & Cardoso, 1999b;Neumann & George, 2005).…”

Landfarmed oil sludge as a carbon source for Canavalia ensiformis during phytoremediation

“…Plant uptake and metabolism are influenced and controlled by molecular configuration and size of the chemical compound; the capability of the plant species is also a strong influence in the uptake process (Harms et al 2003). Jack beans have been used in the phytoremediation of cadmium-contaminated sites (Andrade et al 2005). Consequently, the current study investigated whether soil treated with landfarmed oil sludge provided an extra supplement of a carbon source for jack beans during the phytoremediation of the residual aliphatic and aromatic hydrocarbons from the sludge.…”