Nc. Besnard et F. Larher, PHYTOCHELATINS AND GLUCOSINOLATES ACCUMULATION IN SEEDLINGS OF BRASSICA-NAPUS TREATED WITH CADMIUM CHLORIDE, Phyton, 32(3), 1992, pp. 19-24
Thirty days old seedlings of Brassica napus var. oleifera were submitt
ed to short term treatments with CdCl2 in order to investigate the eff
ect of this heavy metal on sulfur channelling for both phytochelatins
(PC) and glucosinolates (GLS) synthesis and accumulation. PC peptides,
from the roots, containing 2 to 5 gamma-glutamyl-cysteinyl units were
characterized and their individual content determined in relation to
both treatment durations and CdCl2 concentrations. PC synthesis was de
tectable 1 hour after the onset of the treatment, being then maintaine
d at a constant rate until reaching a level related to CdCl, concentra
tion in the external medium. A maximum PC level of 1.28 mumol SH g fre
sh weight-1 was obtained after a 48 h treatment with 150 muM CdCl2. Th
e relative levels of various PCs remained constant except for low conc
entrations (below 10 muM) and in treatments shorter than 15 h. In thes
e cases, the relative abundance of PC2 and PC3 are increased. PC accum
ulation in rapeseed was prevented when CdCl2 and buthionine sulfoximin
e were applied together. This inhibitory effect was abolished with the
glutathione addition. Thus, it is concluded that the processes involv
ed in PC synthesis and accumulation by rapeseed roots are quite simila
r to that occurring in a number of other species. Preliminary results
obtained for GLS stored in vegetative parts of young rape plants treat
ed with CdCl2 suggest that sulfur consumption for PC synthesis did not
occur at the expense of the sulfur available for GLS synthesis since
the effects induced by Cd were not significant.