Mycorrhizal effectiveness and manganese toxicity in soybean as affected by soil type and endophyte

Abstract

Mycorrhizal plants may present Mn toxicity alleviation and this depends on the plant-endophyte-environment interaction. The effectiveness of three arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, G. etunicatum, G. intraradices) and a control without AMF in two soils: Typic Rhodudalf with high Mn availability and a Typic Quartzipsamment, with low Mn availability, was evaluated in a time-course experiment at 3, 6, 9 and 12 weeks after soybean (Glycine max L.) seedling emergence. The objective was to select the most effective AMF species to enhance plant growth and to assess its effects upon Mn uptake by plants and Mn availability in the soil. For the sandy soil, AMF inoculation resulted in increased plant biomass, especially with G. intraradices and G. etunicatum. Lower Mn concentrations were observed in shoot and root of mycorrhizal plants. For the clayey soil, there was also an increase in plant biomass, but only for plants inoculated with G. intraradices and G. etunicatum. Mycorrhizal plants presented higher Mn concentrations in shoot and root and there was an increase of available Mn in the soil, in relation to the control, especially in the treatment with G. macrocarpum. When inoculated with G. macrocarpum, plants presented Mn toxicity symptoms and reduced biomass in comparison to control plants. The effects of mycorrhizal inoculation, either positive or negative, were most intense at 9 and 12 weeks.

Mycorrhizal efficiency in acerola seedlings with different levels of phosphorus

“…These decreases were similar to those observed in castor bean mycorrhizal plants (Machineski, 2008). The mechanisms responsible for Mn toxicity attenuation in mycorrhizal plants are not entirely known; however, as suggested by Nogueira and Cardoso et al, (2003), the alleviation of Mn toxicity in the mycorrhizal plants is not due exclusively to the AMF but is also a result of the changes in host physiology, which reflect the microbial community and the biological processes of Mn oxidation and reduction reactions. It has been suggested, however, that some results prove that manganese can be retained in AMF mycelium hyphae in order to be complexed by polyphosphate granules in the mycelium fungi or oxidized in the plant roots (Smith and Read, 1997;Cardoso et al 2003).…”

“…The decrease of Mn content due to AMF has been observed previously in soybean and castor bean plants. The study in soybeans showed that mycorrhizal plants showed a decrease in Mn content of up to 48% in the shoots and about 51% in the roots (Nogueira, 1999;Nogueira and Cardoso, 2003). These decreases were similar to those observed in castor bean mycorrhizal plants (Machineski, 2008).…”

“…Under these conditions, AMF may contribute to using smaller amounts of fertilizer, the better development and nutrition of the plants, the abbreviation of the transplant time to the field and the increased survival of seedlings in the field (Saggin Júnior and Siqueira, 1996). The effect of mycorrhizae in increasing the growth of the plant has been well documented by several workers for different crops (Saggin Junior and Siqueira, 1996;Balota et al, 1997;Nogueira and Cardoso, 2003;Costa et al, 2005). Although there are few studies on the acerola crop, it has been observed that acerola seedlings show higher growth due to mycorrhizal symbiosis (Chu, 1993;Costa et al, 2001).…”

Manganese soil and foliar fertilization of olive plantlets: the effect on leaf mineral and phenolic content and root mycorrhizal colonization

“…Accordingly, Mn excess may have caused stress at a physiological level and triggered an increase in arbuscular colonization as an early defense response to overcome Mn stress. A greater arbuscular abundance may be generally linked to stressful conditions, including Mn toxicity as reported for other crops . A time delay up to 2 months for increased arbuscule colonization, which is provoked by excess Mn concentrations (at 90 DAT), is comparable to the arbuscular response to some other abiotic stress, such as P deficiency .…”

Role of Arbuscular Mycorrhizal Fungi in Alleviation of Acidity Stress on Plant Growth

“…Nogueira and Cardoso (2003) investigated the effectiveness of three AM fungi (Glomus macrocarpum, C. etunicatum, and R. intraradices) on soybean in two different soils (sandy and clay). The results of this study showed that soybean plants had lower Mn content and biomass in sandy soil compared to clayey soil.…”