Morphological and kinetic parameters of the uptake of nitrogen forms in clonal peach rootstocks.

Peach (Prunus persica L.) rootstock cultivars are typically selected for scion compatibility, ease of propagation, vigor, development, flowering season, yield, low need for cold temperatures, resistance to diseases, effects on the physical-chemical characteristics of the fruit, plant longevity and adaptation to adverse edaphoclimatic conditions. However, kinetic parameters related to nutrient uptake efficiency are usually not considered, such as those of nitrate (NO3 −) and ammonium (NH4 +). N is the nutrient that most impacts growth and yield. The objective of this study was to show the importance of the kinetic parameters of NO3 − and NH4 + uptake as additional criteria for selecting peach rootstocks. The experiment was conducted in a greenhouse. Three rootstock (?Aldrighi?, ?Tsukuba1? and ?Clone 15′) were grown for 30 days in a pot containing 0.1 mol L-1 CaSO4 solution to reduce internal reserves of N. Afterwards, the plants were placed in Hoagland nutrient solution, where periodic collections of the nutrient solution were carried out for three days and the concentrations of NO3 − and NH4 + were determined. After the third day of collecting the solution, the plants were collected and then separated into leaves, roots and stems. Dry matter and total N content were assessed. The kinetic parameters related to NO3 − and NH4 + uptake (maximum uptake rate - Vmax, affinity constant - Km, Minimum concentration - Cmin, Influx - I) were calculated using Cinética software. The most efficient rootstock for NO3 − and NH4 + uptake was ?Tsukuba1?, as it showed the lowest values of Cmin and Km and the highest values of Vmax and Imax for NO3 − and NH4 +. NO3 − uptake in ?Tsukuba1? and ?Aldrighi? showed a two-phase uptake pattern, suggesting the presence of low and high affinity transport systems. On the other hand, NH4 + uptake in the three cultivars apparently followed a one-phase uptake pattern, suggesting the presence of a high affinity transport system. The kinetic parameters of NO3 − and NH4 + uptake are additional criteria that can be used in selecting peach rootstocks, as they directly influence shoot and root dry matter production and N accumulation in leaves.