Effects of Pseudomonas fluorescens DF57 on growth and P uptake of two arbuscular mycorrhizal fungi in symbiosis with cucumber

The effect of Pseudomonas fluorescens DF57 on growth and P uptake of two ar buscular mycorrhizal (AM) fungi in symbiosis with cucumber plants was studi ed in compartmentalised growth systems. Hyphae of Glomus intraradices Schen ck & Smith (BEG87) or G. caledonium (Nicol. & Gerd.) Trappe & Gerdeman (BEG 15) grew into lateral root-free compartments. Non-mycorrhizal plants served as control. The soil in half of the growth units of each mycorrhizal treat ment was inoculated with P, fluorescens DF57. P. fluorescens DF57 enhanced hyphal length density of one of the AM fungi, G. caledonium, but this was n ot reflected in a higher hyphal transport of P from the root-free soil to t he plant. The total P content was higher in plants grown in symbiosis with G. intraradices than in plants in the other treatments, G. caledonium and P . fluorescens DF57 had a synergistic effect in that total P content in plan ts inoculated with G. caledonium was higher in the presence than in the abs ence of P. fluorescens DF57.