Influence of P and Cd on the spore germination, hyphal growth and polyphosphate accumulation in extraradical hyphae of Glomus intraradices

Arbuscular mycorrhizal fungi (AMF) can significantly enhance the resistance of plants to heavy metal, and polyphosphate (PolyP) in the hyphae may be involved in the formation of this resistance. Spores of Glomus intraradices were used as experimental material. The sterilization condition was optimized, and the influence of P and Cd2+ on the spore germination, hyphal growth and polyphosphate in external hyphae of G. intraradices was studied. The results indicated that the spore sterilization in the mixture of 1% chloramine T, 0.02% streptomycin, 0.01% gentamicin and 1/100 (V/V) TW-20 for 5min showed the best effect. Spore germination, hyphal branching and hyphal length decreased with the increase of Cd2+ concentration. The spore germination rate was 0% when the Cd2+ concentration reached 0.1mmol/L, indicating the tolerance limit of spores to Cd2+ at 0.1mmol/L. P at 1mmol/L increased hyphal branching, but decreased spore germination rate and did not affected the hyphal length. All three parameters did not change after the incubation for 23 days. PolyP content in extraradical hyphae increased in response to the elevation of P. Under the Cd2+ stress, PolyP content decreased, while hyphal density increased with PolyP content rising, suggesting an important role of PolyP in the alleviation of heavy metal toxicity.