Correlations between Kinetic Parameters of Phosphate Uptake and Internal Phosphorus Concentrations in Maize Plants: Making it Possible to Estimate the Status of Phosphate Uptake according to Shoot Phosphorus Concentrations

Abstract

The relationship between internal phosphorus (P) concentration P] and kinetics of phosphate (Pi) uptake was investigated in maize seedlings grown hydroponically at different Pi concentrations (0.1–1,000 µM) and in the phase of Pi deprivation (0–10 d). The results indicated when the internal P] was higher than 85 µmol g^?1 dw, apparent K_m, C_min, and V_max were significantly (P<0.01) related to P]s in shoots and roots; when the internal P] was lower than 85 µmol g^?1 dw, K_m and C_min were small and only V_max was significantly related (P<0.01) to internal P]s. Three equations were deduced from the linear regressions of the kinetic parameters and P]s in shoots. Using these equations, the values of apparent K_m, C_min, and V_max of Pi uptake of seedlings grown in different circumstances were calculated according to P]s in shoots. In all the circumstances involved, for K_m and C_min, there was a parallel relationship between the values estimated by P]s in shoots and by the Pi‐depletion technique; for V_max, the values estimated by P]s in shoots were consistent with those obtained from Pi‐depletion experiments except the period of supplying Pi to the Pi‐starved seedlings over several days. These results indicated it is possible to estimate the Pi‐uptake status according to shoot P concentrations in maize plants under experimental conditions, which might be helpful to estimate in‐season status of Pi uptake of maize plants in the field.