The use of mechanistic models based on principles of solute transport may be of great utility to estimate, for example, the impact of eucalypt forest cultivation on the pools and fluxes of nutrient in soils. Among the parameters required by such models are the values of the ion absorption kinetics constants Vmax, Km and Cmin. Thus, the objective of this study was to determine the values of Vmax, Km and Cmin for K, Ca and Mg, as well as to evaluate the nutritional efficiency of eucalypt clones to these nutrients. The present study consisted of three experiments in solution culture (one for each cation). It was employed four genetic materials (clones 7074, 57, 1213 and 129) originated from clonal propagation. Clone 1213 is an Eucalyptus grandis x Eucalyptus urophylla hybrid, whereas the others are natural hybrids of E. grandis. The concentration of each nutrient being studied in the depletion solution at specific sampling times, initial and final pot solution volume and fresh root weight were used in order to obtain the value of the kinetics constants. For K, clone 7074 showed the lowest Vmax value in relation to the other clones, which did not differ among themselves. All clones did not differ statistically in relation to Km and Cmin for K. For Ca, the studied clones differed in relation to the values of Vmax and Km but, they did not differ for Cmin. The lower values of Km for Mg were observed for the clones 57 and 7074, that is, the carrier proteins at the root cells plasma membrane have a high affinity for this nutrient. Nevertheless, the values of Vmax and Cmin did not differ among the studied clones. Differences in nutritional efficiency of the studied clones in relation to K and Ca were due to differences in the absorption efficiency and for Mg were related with differences in the nutrient use efficiency and absorption efficiency.
Mechanistic models; kinetics constants; absorption efficiency; utilization efficiency; Eucalyptus grandis; Eucalyptus urophylla
