Short-chain polyphosphate in arbuscular mycorrhizal roots colonized by Glomus spp.: A possible phosphate pool for host plants

We investigated the relationship between plant growth and polyphosphate (poly P) content in Allium fistulosum roots colonized by Glomus sp. R10 or Glomus etunicatum with different levels of phosphate addition. Poly P was quantified by two enzymatic assays: long-chain poly P (>∼20 inorganic phosphate [Pi] residues) with polyphosphate kinase, and total poly P with polyphosphate exopolyphosphatase. The difference between these values was designated as short-chain poly P (<∼20 Pi residues). The content of long-chain poly P in mycorrhizal roots and plant growth was poorly correlated or not, depending in fungal species. However, the content of short-chain poly P and plant growth was highly correlated in both species. This difference suggests that short-chain poly P in mycorrhizal roots colonized by Glomus spp. functions as a pool of Pi for the plant.