Considerações referentes à determinação de parâmetros cinéticos de absorção de fósforo
Keywords:
absorção iônica, solução nutritiva, parâmetros cinéticos, concentração de fósforo, crescimento radicularAbstract
Considerations are given to the determination of kinetic parameters of phosphorus uptake by soybean plants. Estimating kinetic parameters of P uptake, such as Vmax and Km, using models as those proposed by LineweaverBurk, Hanes-Woolf, and Hofstee have resulted in erratic values. These errors are obtained whether all observed points, particularly those corresponding to the initial phase of the uptake period, are included or deleted. Some possible reasons for this fact are discussed. Equations for estimating the kinetic parameters by use of these models are presented. In order to overcome this problem, the use of a graphic-mathematical approach is suggested, which permits the estimation of consistent values of Vmax and Km of P uptake by soybean plants.
References
ALVES, VM.C. Efeito do alumínio sobre a cinética de absorção e translocação de fosfato e sobre o crescimento e composição mineral de dois cultivares de trigo. Viçosa, U.F.V., 1084. 45 p. (Tese M.S.).
ANGHINONI, 1. & BARBER, S.A. Phosphorus influx and growth characteristics of corn roots as influenced by phosphorus supply. Agron. J. 72:685-688. 1980.
CANAL, LN. & MIELNICZUK, J. Parâmetros de absorção de potássio em milho (Zea mays L.), afetados pela interação aluminio-calcio. Ciéncia e Cultura 35:336-340, 1983.
CASTELLS, A. Absorção de fosforo e de cálcio como critério de seleção de genótipos de soja (Glycine max (L.) Merrill) quanto à tolerância ao alumínio. Viçosa, Universidade Federal de Viçosa, 1984. 62 p. (Tese M.S.).
CLAASSEN, N. Development and verification using measured soil and plant parameters of a mathematical model for nutrient flux to plant roots growing in soil. Purdue University, 1975. 157 p. (Ph.D. Dissertation).
CLAASSEN, N. & BARBER, S.A. A method for characterizing the relation between nutrient concentration and flux into roots of intact plants. Plant Physiol. 54:564-568. 1974.
HOFSTEE, B.H.J. On the evaluation of constant Vm and Km in enzyme reactions. Science 116:329-333. 1952.
JUNCK, A. & BARBER, S.A. Plant age and the phosphorus uptake characteristics of trimmed and untrimmed corn roots systems. Plant Soil 42: 227-239. 1975.
LINEWEAVER, H. & BURK, D. The determination of enzyme dissociation constants. J. Amer. Chem. Soc. 56:658-666. 1934.
NYE, P.H. & TINKER, P.B. Solute movement in the soil-root systems. Studies in Ecology — Vol. 4 Berkeley, University of California Press, 1977. 342 p.
OLIVEIRA, R.F. & MIELNICZUK, J. Caracterizacdo de trés cultivares de soja (Glycine max (L.) Merrill) quanto a eficiéncia de absorção e utilização de K. Agron. Sulriogr. 14:251-260. 1978.
RUIZ, H. Estimativa dos parâmetros cinéticos Km e Vmax por uma aproximação grafico-matematica. Rev. Ceres 32.79-84. 1985.
RUSSELL, R.S. & SANDERSON, J. Nutrient uptake by different parts of the intact roots of plants. J. Exp. Bot. 18:491-508. 1967.
SCHENK, M.K. & BARBER, S.A. Potassium and phosphorus uptake by corn genotypes grown in the field as influenced by root characteristics. Plant Soil 54:65-76. 1980.
VILELA, L. & ANGHINON], 1. Morfologia do sistema radicular e cinética da absorção de fosforo em cultivares de soja afetados pela interação aluminio-fosforo. R. Bras. Ci. Solo 8:91-96. 1984.
