Dados do Trabalho

Título

PHOSPHORUS ACCUMULATION IN EUCALYPT SEEDLINGS SUPPLIED WITH PHOSPHORUS AS ORGANIC SOURCES IS INCREASED BY ARBUSCULAR MYCORRHIZA

Resumo

Because phosphorus (P) is commonly a limiting nutrient to plants and organic P can represent up to 50% of the total P in soils, studies about the ability of plants to use organic forms of P are needed. The mineralization of organic P is due to the combined effects of plants, soil microbes and arbuscular mycorrhizal (AM) fungi, and contributes to the plant P uptake. We studied the ability of Eucalyptus globulus and E. grandis, and the contribution of AM to use P from five organic sources: phytate, ATP, glucose-6-phosphate (G6P), RNA, bacterial necromass (BN), and potassium phosphate (PP), a inorganic P, and iron phosphate (FeP), as sparingly soluble P. A glasshouse experiment (25-34 °C) in pots with sterilized sand was performed in a 2x2x7 factorial scheme: 2 plant species, 2 AM treatments and 7 P sources. Plants were irrigated with 0.1 mM P solutions of each of the P sources and allowed to grow for 12 weeks. We measured: shoot biomass, the activities of root phytase and phosphatase (rAPase), AM mycelium phosphatase (mAPase) and shoot P content. While mycorrhization did not promote plant growth, AM plants showed higher shoot P contents than non-AM ones. AM plants of E. globulus had greater rAPase and phytase activities when supplied with phytate as sole P source; ATP and G6P also promoted higher phytase activity. AM plants of E. grandis supplied with phytate had the highest rAPase activity. The mAPase was higher when plants were supplied with BN, which produced the longest extraradical mycelium (ERM). Plants that received phytate had lower shoot P contents, but greater P use efficiency. BN as P source stimulated AM establishment and ERM growth. The results support that the phosphatase activity of eucalypt roots is higher when the plants are exposed to more recalcitrant sources of P, such as phytate, or less soluble ones, such as FeP, conditions in which plants has low accumulation of P, leading to more intense expression of strategies to cope with P limitation.  

Palavras-chave

phytate; phosphatases; plant mineral nutrition.

Instituição financiadora

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Processo: 2021/05815-9