This study aimed to evaluate organic translocation, physiologic indexes of growth analysis and essential oil yield of Mentha piperita L. cultivated in nutrient solution with varying levels of N, P, K and Mg. Thus, four treatments were evaluated: 50% N, P, K, 25% Mg; 50% N, P, K, Mg; 65% N, 50% P, 25% K, 100% Mg; and 100% N, P, K, Mg. Organic translocation was assessed through leaf mass ratio (LMR) and dry matter distribution to the different organs. The physiologic indexes leaf area ratio (LAR), specific leaf area (SLA), net assimilation rate (NAR) and relative growth rate (RGR), derived from growth analysis, were estimated using the software ANACRES, following the quadratic exponential fitting of leaf area and dry mass of leaves and total plant, relative to time. Essential oil yield was calculated as percentage after extraction from shoot using hydrodistillation. Plants subjected to the treatment with complete level of nutrients (100%N/P/K/Mg) less efficiently exported organic material from the leaf and LMR showed slower decrease due to the longer retention of such material in its production site. Besides, those plants did not present higher productivity and NAR and RGR curves showed slower decrease. Plants subjected to the treatment with 65%N/50%P/25%K/100%Mg had adequate organic matter exportation from the leaves to the stem and petioles, as demonstrated by LMR and dry matter distribution to these organs. Also in these plants, LAR was higher at the initial development and lower at 94 DAT, indicating leaf shading as a result of growth, and SLA showed less variation during the cycle, reflecting more homogeneous leaf thickness. NAR and RGR had decreasing curves, with marked falls relative to the remaining plants. All these indexes indicate higher productivity of plants subjected to the treatment with 65%N/50%P/25%K/100%Mg, which also had higher essential oil yield, on average, during the cycle. In conclusion, 35% reduction for N, 50% for P, 75% for K (65%N/50%P/25%K/100%Mg) is recommended for cultivation and essential oil extraction of M. piperita.
Mentha piperita; essential oil; mineral nutrition; hydroponics
