Kinetic, morphophysiological, and biochemical parameters as a strategy to select clones of Eucalyptus spp. more efficient in phosphorus uptake

Eucalyptus clones are typically selected based on their rooting capacity, wood quality, and resistance to drought, frost, and disease. However, kinetic, morphophysiological, and biochemical parameters that determine the uptake efficiency of nutrients such as phosphorus (P) are often not considered in breeding programs. This study aimed to select Eucalyptus clones based on P uptake efficiency using kinetic, morphophysiological, and biochemical parameters. The experiment was set up in a 2 × 3 factorial arrangement, the first factor being P levels: 16.5 mg P L-1 (high P) and 4.65 mg P L-1 (low P) in half-strength Hoagland’s nutrient solution, and the second factor being three Eucalyptus spp. clones (E. saligna, E. urograndis, and E. dunnii), with six replications per treatment. Kinetic parameters (Vmax, Km, Cmin and I), as well as morphological parameters in shoots and roots, biomass production, P concentrations in tissues, photosynthetic parameters, chlorophyll a fluorescence, photosynthetic pigments, metabolic enzyme activity and oxidative stress were evaluated. Eucalyptus saligna showed the highest P influx rates and the lowest values of Cmin, while E. urograndis presented the lowest values of Km under low P supply. Both E. saligna and E. urograndis resulted more efficient at phosphorus uptake, indicating P absorption efficiency at low concentrations. Eucalyptus dunnii showed the highest values of Km and Cmin for P, indicating adaptation to environments with greater P availability. Thus, P kinetic parameters could be used in Eucalyptus selection and breeding programs, as they assist in predicting P uptake in environments with different concentrations of this nutrient.