Kinetics of l-Alanine Escape from Xylem Vessels
AUTOR(ES)
van Bel, Aart J. E.
RESUMO
Labeled (3H or 14C) l-alanine was perfused through the xylem vessels of isolated tomato internodes (Lycopersicon esculentum cv. Moneymaker) at various concentrations (10−6 molar to 10−2 molar). At each concentration the escape of l-alanine from the xylem vessels was apparently a first order process, which is in agreement with Horwitz' (1958, Plant Physiology 33:81-93) model for irreversible escape from the xylem vessels. The escape constant (K) decreased at higher concentrations of l-alanine, which implies that Horwitz' model is inappropriate to describe the kinetics of l-alanine escape, and that the escape at least partly is a saturable process. To obtain data that relate the concentration of l-alanine in the xylem vessels and the escape rate of the amino acid, average escape rates per internode were measured and the corresponding concentrations were calculated from the integrated form of the Michaelis-Menten equation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=542806Documentos Relacionados
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