Changes in the fresh and dry weight of leaf blades, petioles, internodes, a
nd their ion concentrations as well as rates of root exudation were investi
gated in cucumber grown in hydroponic culture and treated with physiologica
l concentrations of lead (Pb). The growth of flowering cucumber supplied wi
th FeCl3 shows a typical bell-shaped curve derived from leaf dry weights, w
here the 4th, 5th, and 6th leaves are the largest ones. Lead inhibited grow
th up to 20% (except the youngest leaves which were stimulated), but did no
t cause morphological changes. Whereas root growth was also retarded by abo
ut 20%, exudation was inhibited to 50%, that is, the root resistance to wat
er transport was increased by Pb. In spite of that the dry matter yield of
internodes and petioles hardly reached 10 and 5% of that of leaf blades, re
spectively, their calcium (Ca), magnesium (Mg), and zinc (Zn) concentration
s were almost the same. Similarly, the concentrations of these metals in th
e specific leaf blades are equal despite their different growth characteris
tics but the concentration of Mn is independent of the growth of the examin
ed tissues. Lead was the only cation to accumulate in the largest leaves. T
he inhibitory effect of ph on ion uptake was proportional to the growth inh
ibition of the tissues except manganese (Mn), the accumulation of which was
stimulated by Pb in all the analyzed tissues and copper (Cu) which increas
ed only in the internodes. We could not explain the extremely different ion
distributions observed during the growth of cucumber. However, it is evide
nt that the measurement of ion concentrations at whole shoot level is not e
nough to characterize ion interactions because only some ions accumulate at
the same rate as tissues grow. These ions maintain stable concentration le
vels in shoot parts whereas others decrease or increase independently from
growth.