Mycorrhiza influence on maize development under Cd stress and P supply

Abstract

The role of arbuscular mycorrhizal fungi (AMF) on cadmium (Cd) accumulation and on the possible attenuation of Cd stress was studied in maize plants (Zea mays L. var. Exceller). Plants inoculated or not with Glomus macrocarpum were exposed to Cd (0-20 µmol L -1 ), at two P levels (5 and 10 mg L -1 ) in the nutrient solution. The experiment was conducted in a hydroponic system, using a randomized 2 x 2 x 2 factorial design. The mycorrhiza-Cd interaction on plant growth, nutrients and Cd accumulation, AMF root colonization and on extra-radical mycelium was investigated. Mycorrhiza promoted plant growth whereas Cd addition reduced plant biomass production. No difference in plant Cd concentrations was found between mycorrhizal (M) and non-mycorrhizal (NM) plants, where Cd accumulated mainly in roots. In general, roots showed a slightly higher Cd concentration in the cell wall than in the cytoplasmic fraction, with M roots presenting 26% more Cd in the cell wall fraction than NM roots. Mycorrhizal plants showed higher P/Cd, N/Cd and S/Cd ratios in shoots and roots compared to NM plants. Mycorrhizal colonization and the length of extra-radical mycelium were diminished by Cd addition, the reduction being more pronounced under high-P supply. Addition of Cd induced guaiacol peroxidase (GPOX) activity in roots; however, M plants, in addition to the higher root protein contents, showed no induction of GPOX activity in the presence of Cd, suggesting higher tolerance to Cd. It is concluded that Cd affected mycorrhizal symbiosis by decreasing root colonization and the development of the extraradical mycelium. Nevertheless, the higher growth and nutrients/Cd ratios observed in M plants indicate an efficient symbiosis capable of alleviating Cd stress. Key words: arbuscular mycorrhizal fungi, Cd distribution, extra-radical mycelium, heavy metals, peroxidase, phosphorus Micorriza influencia o desenvolvimento do milho sob estresse de Cd e suprimento de P: A influência dos fungos micorrízicos arbusculares (FMA) no acúmulo e na atenuação potencial do estresse causado pelo Cd foi estudada em plantas de milho (Zea mays L. var. Exceller). Plantas associadas ou não com o FMA Glomus macrocarpum foram expostas ao Cd (0-20 mmol L -1 ) em dois níveis de P (5 e 10 mg L -1 ), em solução nutritiva. O experimento foi conduzido em sistema hidropônico, com delineamento totalmente casualizado, em esquema fatorial 2 x 2 x 2. Avaliou-se o efeito da interação micorriza-Cd sobre o crescimento da planta, o acúmulo de Cd e de nutrientes, a colonização micorrízica da raiz e a produção de micélio extra-radical. A micorriza promoveu o crescimento da planta enquanto a adição de Cd reduziu a produção de biomassa vegetal. Não foram observadas diferenças nas concentrações de Cd de plantas micorrizadas (M) e não-micorrizadas (NM), acumulando-se o Cd principalmente nas raízes. Em geral, as raízes mostraram maior concentração de Cd na fração da parede celular do que na citoplasmática, sendo que raízes de plantas M apresentaram quantidade de Cd 26% maior na fração...

Cadmium Remediation by Arbuscular Mycorrhizal Fungus–Colonized Celery Plants Supplemented with Ethylenediaminetetraacetic Acid

“…Similar to this, a reduction in the colonizing ability of G. mosseae with increase in the HM concentration in soil has also been reported earlier by Citterio et al (2005) and Marques et al (2008). However, an efficient symbiosis capable of alleviating Cd stress was detected in our study, which is comparable to the results of Andrade and Silveira (2008), who also reported that Cd addition decreased the AM root colonization of plants and the development of intraradical mycelium besides alleviating Cd stress. Moreover, chelate toxicity was also noticed on addition of EDTA against G. mosseae, as AM spore number and AM colonization were reduced.…”

Arbuscular mycorrhiza confers Pb tolerance in Calopogonium mucunoides

“…Plants possess different tolerance mechanisms to the high levels of Pb and other HMs in soils; among them, the association with the symbiotic arbuscular mycorrhizal (AM) fungi may confer tolerance to more sensitive species due to the increase in the absorption and utilisation of phosphorus (P) by mycorrhizal (M) plants (Chen et al 2005;Andrade and Silveira 2008;Soares and Siqueira 2008). An interesting feature of AM association is that it can increase or decrease the absorption capability of HMs by the plant (Ma et al 2006;Andrade et al 2004).…”

Colonização micorrízica e atividade de fosfatases ácidas na rizosfera de cultivares de cana-de-açúcar após aplicação de herbicidas

“…No entanto, alguns fatores influenciam as associações micorrízicas, como a textura do solo; a calagem (Carrelho et al, 2007); o sistema de cultivo (Dawo et al, 2009); a contaminação do solo com metais pesados (Andrade & Silveira, 2008); as queimadas realizadas para a colheita de cana-de-açúcar (Reis et al, 1999); e os agrotóxicos, a exemplo dos herbicidas (Abd-Alla et al, 2000;Santos et al, 2006;Vieira et al, 2007), com respostas variadas em função do composto químico e da espécie de planta em questão (Bethlenfalvay et al, 1996).…”