Two-day-old maize seedlings were incubated in the presence or absence
of 1 mM spermidine in the external medium. After 2 h, an increase of p
otassium (K+) efflux from roots was observed in treated seedlings up t
o a maximum after a 4 h treatment, decreasing to control values in the
following hours. Simultaneously, an inhibition of K+ uptake occurred
in roots from treated seedlings up to minimum values after 7-9 h treat
ment. Successively, roots from treated seedlings progressively recover
ed their K+ uptake capacity up to values about 50% higher than control
seedlings. No variations in K+ content were observed after 24 h betwe
en control and spermidine-treated seedlings taken as a whole, while th
e K+ content of roots and shoots showed different values when individu
ally analysed. Our results suggest that for spermidine-treated plants,
the K+ content is mantained constant after 24 h by an equilibrium of
the influx/efflux systems while a different K+ content in shoots and r
oots is related to a different growth rate induced by the presence of
spermidine in the external medium.