02144naa a2200217 a 450000100080000000500110000800800410001902400570006010000180011724501610013526000090029652014370030565000130174265300200175565300160177565300210179165300190181270000170183170000140184877300640186219300672023-02-16       2012    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1590/S0103-901620120005000022DOI1 aSANTOS, P. M.  aAdaptation of the C4 grass Panicum maximum to defoliation is related to plasticity of N uptake, mobilisation and allocation patterns.h[electronic resource]  c2012  aDry mass production and persistence of Panicum maximum pastures depends on nitrogen supply. Defoliation influences N uptake and allocation patterns yet its effects on plasticity of N dynamics in P. maximum have not been investigated. Stable isotopes of N (15N) were used in order to test the hypothesis that defoliation in terms of proportion of the leaf area removed effects N mobilisation, uptake and allocation patterns in P. maximum. The plants were initially cut weekly to a height of either 0.15 m or 0.30 m for seven weeks. Eight weeks after the first defoliation, all plants were defoliated for a final time to remove 0, 25, 50, 75 or 100 % of the area of each individual leaf blade of the main tiller. Root N uptake was reduced when all leaf area was removed, but more lenient defoliation improved N uptake due to a positive effect on specific N uptake. Young leaves, side tillers and roots were the main sinks for N from root uptake. Roots of P. maximum became a net source of N for mobilisation immediately after severe defoliation. Root uptake was the main source of N for new growth in P. maximum plants. Allocation pattern of mobilised N was different from that of N derived from root uptake. It was concluded that adaptation of P. maximum to defoliation is related to plasticity of N uptake, mobilisation and allocation, but changes in N dynamics did not offset negative impacts of complete defoliation of the plants.  aregrowth  aClipping height  aGuineagrass  aOrganic reserves  aTropical grass1 aTHORNTON, B.1 aCORSI, M.  tScientia Agricolagv. 69, n. 5, p. 293-299, sep./oct. 2012.