Young shoot discs of sweet cherry (Prunus avium L.) were sampled at va
rious dates from elongating internodes of vigorous shoots and incubate
d for 4 days in 0.04 mM paraquat (1,1-dimethyl-4,4-bipyridinium dichlo
rid). The histochemical response was a massive deposition of flavanols
along the outer margin of cells of pith, phloem and cortex. Even the
outer cambium layer responded in this way. Flavanol inclusions in the
cortex disappeared upon addition of paraquat. The paraquat effects des
cribed were reversed by addition of 0.16 mM (+)-catechin to paraquat i
n the incubation medium. Similar treatments were performed with small
discs of mature leaves indicating a massive displacement of the cytopl
asm by paraquat which again was overcome by (+)-catechin. Epicatechin,
(+)-catechin as well as five proanthocyanidins could be identified by
HPLC-CRD techniques from leaves and phloem of cherry. The possible fu
nctions of(+)-catechins and their oligomeric forms in preserving the n
ormal cellular organization were discussed.