Actual escape area and lateral escape from the xylem of the alkali ions Na + , K + , Rb + and Cs + in tomato
1985; Wiley; Volume: 65; Issue: 4 Linguagem: Inglês
10.1111/j.1399-3054.1985.tb08675.x
ISSN1399-3054
AutoresH. Th. Wolterbeek, J. van Luipen, Marie L. De Bruin,
Tópico(s)Plant nutrient uptake and metabolism
ResumoApproximation of the total escape area of the xylem in an inbred line of tomato (Ly‐copersicon escutentum Mill. cv. Tiny Tim) with help of the frequency distribution of xylem vessel radii provides the possibility to calculate realistic escape constant values from uptake experiments of several elements into tomato stem segments. Comparison of the lateral escape rates of 24 Na + , 42 K + , 86 Rb + and 134 Cs + indicate that Na + escape is rate‐limited by its uptake into a rather constant number of surrounding cells, regardless of changes in the total escape area of the xylem vessels. The escape of K + , Rb + and Cs + seems to be proportional to the surface area of the xylem vessels and their escape is apparently controlled by their transport across the cell walls of the transport channels. The calculated small values for the escape rate constants (apparent permeability of the xylem cell walls, ca 2–3 · 10− 9 m s− 7 ) are probably due to the presence of lignin in the xylem cell walls, the discrimination between ions as a result of differing affinities and selectivities and the presence of other solutes in the applied solution.
Referência(s)