Mycorrhizas promote P acquisition of tea plants through changes in root morphology and P transporter gene expression

Abstract

Tea (Camellia sinensis (L.) O. Kuntze) is predominantly grown in acidic soils with severe limitations of P-nutrition. The present study evaluated the effects of an arbuscular mycorrhizal (AM) fungus, Claroideoglomus etunicatum, on root morphology, leaf and root P concentration, phosphatase activity in soils and roots, and the relative expression of root P transporter genes (PT1 and PT4) in Camellia sinensis ‘Fuding Dabaicha’ seedlings in sands under two levels of P viz., 0.5 μM (P0.5) and 50 μM (P50) through Hoagland solutions (pH 4.2) for 24 weeks. Under both P0.5 and P50 conditions, AM seedlings displayed a higher growth performance (shoot biomass, root biomass, and plant height), root morphology (total length, taproot length, 2nd- and 3rd-lateral root number, and volume), and root-hair length, but lower root-hair density than non-AM seedlings. Mycorrhizal inoculation significantly increased root P concentrations in P0.5 and P50 and leaf P concentrations in P0.5 over non-mycorrhizal treatment. The AM seedlings recorded considerably higher soil acid, neutral, and total phosphatase activity under P0.5 treatment, and soil neutral and total phosphatase activity under P50 treatment, compared with the non-AM seedlings. Root acid phosphatase activity was reduced due to mycorrhization at both of P0.5 and P50. AM fungal inoculation up-regulated the relative expression of root CsPT1, while down-regulated the CsPT4 expression in P0.5 and P50 treatments. It was concluded that AM fungal inoculation significantly promoted P acquisition capacity of tea plants, especially in roots through improving root growth and enhancing soil acid phosphatase activity and root CsPT1 expression.