Arbuscular mycorrhizal (AM) fungi increase phosphate (P) uptake by plants. Organic phosphate comprises 30–80% of total P in most agricultural soils. Some plants can utilize organic phosphate by secreting acid phosphatase (ACP) from their roots, especially under low P conditions. Although secretion of ACP from extraradical hyphae of AM fungi has been reported, the specific factors that affect the secretion of ACP are unknown. The objective of the present study was to investigate whether secretion of ACP from extraradical hyphae is induced by low P conditions. First, specimens of Allium fistulosum were either inoculated with the AM fungus Rhizophagus clarus strain CK001 or remained uninoculated and were grown in soil with 0.5 g P₂O₅ kg⁻¹ soil or without P fertilization using two-compartment pots. Soil solution was collected using mullite ceramic tubes 45 days after sowing. The soil solution was analyzed for ACP activity by using p-nitrophenylphosphate. Second, Ri T-DNA transformed roots (i.e., hairy roots) of Linum usitatissimum inoculated with R. clarus were grown on solid minimal media with two P levels applied (3 and 30 μM P) using two-compartment Petri dishes under in vitro conditions. Hyphal exudates, extraradical hyphae, and hairy roots were collected and analyzed for ACP activity. ACP activity in the soil solution of the hyphal compartment in the A. fistulosum inoculation treatment was higher without P fertilization than with P fertilization. AM colonization also was higher without P fertilization than with P fertilization. In the in vitro two-compartment culture, ACP activity of hyphal exudates and extraradical hyphae were higher under the 3-μM treatment than under the 30-μM treatment. These findings suggest that the secretion of ACP from the extraradical hyphae of R. clarus into the hyphosphere is promoted under low P conditions.

中文翻译：

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丛枝菌根真菌根际菌丝的根外菌丝分泌酸性磷酸酶可调节磷酸盐的利用。

丛枝菌根（AM）真菌会增加植物对磷酸盐（P）的吸收。在大多数农业土壤中，有机磷酸盐占总磷的30-80％。一些植物可以通过从根部分泌酸性磷酸酶（ACP）来利用有机磷酸盐，尤其是在低磷条件下。尽管已经报道了AM真菌根外菌丝分泌ACP，但是影响ACP分泌的具体因素尚不清楚。本研究的目的是调查低磷条件是否诱导了自由基外菌丝分泌ACP。首先，将瘘菌标本接种AM真菌根瘤菌克拉氏菌株CK001或不接种，并在0.5 g P ₂ O ₅ kg的土壤中生长^-1土壤或不使用两室花盆施磷肥。播种45天后，用莫来石陶瓷管收集土壤溶液。通过使用对硝基苯基磷酸酯分析土壤溶液的ACP活性。第二，用R 1接种R 1 T-DNA转化的亚麻亚麻的根（即毛状根）。在体外条件下，使用两室陪替氏培养皿在两个基本水平的固体基本培养基上生长紫红色，并施加两个P水平（3和30μMP）。收集菌丝渗出液，根外菌丝和毛状根，并分析其ACP活性。ACP活动在菌丝车厢在土壤溶液一个。瘘管不施磷肥的接种量要比施磷肥的高。没有磷肥的AM定植也比有磷肥的高。在体外两室培养中，在3μM处理下，菌丝渗出液和自由基的菌丝的ACP活性高于在30μM处理下。这些结果表明，ACP从的根外菌丝分泌[R 。CLARUS入hyphosphere是低磷条件下促进。