Extraradical hyphae of the mycorrhizal fungus Glomus intraradices can hydrolyse organic phosphate

Organic phosphorus sources make a large fraction of the total P in some soi ls. Vesicular-arbuscular mycorrhizal fungi provide a large surface area for the absorption of inorganic P. The question of whether or not they have di rect access to organic P by producing extracellular phosphatases has hither to been controversial because experiments had not been performed in the abs ence of other soil microorganisms. We used a split-dish in vitro carrot myc orrhiza system free from contaminating microorganisms. The extraradical hyp hae of Glomus intraradices hydrolysed both 5-bromo-4-chloro-3-indolyl phosp hate and phenolphthalein diphosphate. Moreover, they transferred significan tly more P to roots when they had access to inositol hexaphosphoric acid (p hytate) than when they did not. Thus we show unequivocally that extraradica l hyphae of G. intraradices can hydrolyse organic P, and, further, that the resultant inorganic P can be taken up and transported to host roots.