Effects of soil phosphorus on spore germination and hyphal growth of arbuscular mycorrhizal fungi

Abstract

The direct effects of soil phosphorus on spore germination and hyphal grov, th of the arbuscular mycorrhizal fungi (AM), Glomus etunicatum Beck. & Gerd., E3 and Scutellospora heterogama (Nicol. & Gerd.) Walker & Sanders, were investigated by nicatis of two soil-agar plate experiments. In the first experiment, the percentage spore germination and h\phal length of G. eturiuaUim, measured at ten different P levels and three pertods of incubation, were affected by the P status of the soil. The best correlation with P level in the soil occurred at 7 d of incubation for spore germination and at 14 d for hyphal growth and hyphal growth increment. Spore germmation was stimulated when 125//gPg ' was applied to tbe soil and decreased with further soil P increments. Hyphal growth decreased significantly with soil P amendments above 37'5//gPg"'. ln the second experiment including three different P levels atid the three AM endophytes, soil P affected spore germination and hyphal growth, and both decreased at the high phosphate treatment for G. etunicatuni and S. heterogama. Tbe E3 spore germination was similar to the other two species, but the hyphal growth was poorer, S. heterogama was more sensitive to P fertilization than the Glomus spp. and for the three species the hyphal production uas not proportional to spore size.

Quantificação de micélio extrarradicular de fungos micorrízicos arbusculares em plantas cítricas: II. Comparação entre diferentes espécies cítricas e endófitos

“…Solo, 23:59-67, 1999 hospedeiros. O efeito negativo de doses de P na colonização radicular por G. intraradices e G. clarum está de acordo com Antunes & Cardoso (1991), Peng et al (1993), Miranda & Harris (1994b), Melloni et al (1996a,b), Nagahashi et al (1996), Gomes (1997) e Nogueira (1997), com hipóteses ligadas à diminuição dos exsudatos radiculares, interferindo no processo inicial de desenvolvimento micelial de FMAs (Graham et al, 1981;Miranda & Harris, 1994a); ao aumento de P foliar com diminuição da permeabilidade radicular à infecção (Thomson et al, 1986;Miranda et al, 1989); à variação do fluxo de carboidratos da planta ao endófito (Buwalda & Goh, 1982;Siqueira et al, 1984); ao aumento da atividade de endoquitinases e de β-1,3 endoglucanases, restringindo a colonização interna (Lambais & Mehdy, 1993;Lambais & Mehdy, 1995), entre outras. O FMA G. etunicatum, apesar de utilizado previamente por Antunes & Cardoso (1991), não demonstrou capacidade de colonização radicular em nenhum dos porta-enxertos utilizados, provavelmente por causa da ineficiência enzimática ou morfológica no processo inicial de infecção radicular.…”

Impact of abiotic factors on development of the community of arbuscular mycorrhizal fungi in the soil: a Review

“…Among the most important factors regulating the dynamics of mycorrhizal development are abiotic environmental factors. Also significant are factors such as temperature, soil pH, humidity and the intensity of light as well as the availability of minerals (Bonfante and Perotto, 1995;Miranda and Harris, 1994;Tahat and Sijam, 2012). The production of spores by AMF causes these fungi to survive and propagate in the soil environment despite the absence of a symbiotic plant.…”

The effects of arbuscular mycorrhizal inoculations and cotyledon removal on early seedling growth of Pongamia pinnata

“…Fewer AMF species was isolated from mollisol at Pantnagar, which could be due to the higher level of P present in the soil. Higher soil P concentration reduces AMF spore production (de Miranda and Harris, 1994;Shukla et al, 2012a), abundance, and diversity (Bhadalung et al, 2005;Antunes et al, 2012).…”