P measurement
Determination of P content in strawberry fruits was performed by the Mo-Sb colorimetric method (Ames, 1966). After the fruits were ground evenly into powder in liquid nitrogen, 1 g fruit powder was digested in the solution including 5 mL concentrated sulfuric acid at 400 ◦C for 10 min, subsequently when the solution was cold, 3 mL 30% hydrogen peroxide was added and then the solution was heated up to 400 ◦C for 30 min. The clear liquor was collected and the total amount of P was determined by the molybdate assay.