G. Guerrier et al., Organic solutes protect drought-tolerant Populus x euramericana against reactive oxygen species, J PLANT PHY, 156(1), 2000, pp. 93-99
The mechanisms by which drought-induced oxidative stress is tolerated in po
plar were appreciated by the ability of leaf extracts to scavenge reactive
oxygen species (ROS) generated in vitro by a xanthine oxidase-hypoxanthine
system. Their effects were detected by the protection towards the denaturat
ion of malate dehydrogenase (MDH) of crude and dialysed extracts of a droug
ht-sensitive (Populus x euramericana Luisa Avanzo) and a drought-tolerant (
I! x euramericana, Dorskamp) poplar exposed to control and osmotic stress (
- 0.336 MPa). At the beginning of the incubation period in presence of ROS,
MDH from crude extract of control Dorskamp was protected against the denat
uration; boiled crude extracts of control Dorskamp also protected MDH from
the dialysed extract of control Luisa Avanzo. In control Dorskamp, cysteine
, proline, polyamines and ascorbate added in vitro were efficient ROS scave
ngers. Compared with the control condition, the rate of MDH denaturation in
presence of ROS decreased in a dialysed extract of stressed Luisa Avanzo b
ut increased in that of stressed Dorskamp. Under stress conditions, proline
in vitro enhanced the rate of MDH denaturation by ROS in Luisa Avanzo, bur
: competed as ascorbate with ROS in Dorskamp. In Dorskamp, the 12 h-exposur
e to osmotic stress resulted in a decrease in catalase and gutathione reduc
tase activities, in an enhancement of superoxide dismutase, ascorbate perox
idase and contents of some putative leaf antioxidants (putrescine and gluta
thione), but did not affect the contents of spermine, spermidine and ascorb
ate. The consequences of extract/solute effects are discussed for each clon
e as regards the drought response.