Cadmium accumulation in sunflower plants influenced by arbuscular mycorrhiza.
In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 micromol L(-1)) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg(-1). Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 microg g(-1) dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues.
de Andrade
Sara Adrián López
SA
Instituto Agronômico-IAC, Centro de Pesquisa e Desenvolvimento de Solos e Recursos Ambientais, Campinas, SP, Brazil.
da Silveira
Adriana Parada Dias
AP
Jorge
Renato Atílio
RA
de Abreu
Mônica Ferreira
MF
D001673:Biodegradation, Environmental; D002104:Cadmium / Q000378:metabolism*; D006368:Helianthus / Q000378:metabolism* / Q000382:microbiology*; D038821:Mycorrhizae / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D012989:Soil Pollutants / Q000378:metabolism
D012989:Soil Pollutants; D002104:Cadmium