L. Willadino et al., POLYAMINE AND FREE AMINO-ACID VARIATIONS IN NACL-TREATED EMBRYOGENIC MAIZE CALLUS FROM SENSITIVE AND RESISTANT CULTIVARS, Journal of plant physiology, 149(1-2), 1996, pp. 179-185
The effect of different NaCl concentrations on maize embryogenic callu
ses derived from immature embryo cultures of a) the salt-sensitive inb
red line W64Ao2, b) the resistant hybrid Arizona 8601 and c) the 0.4 %
NaCl pre-adapted W64Ao2 (WpA) calluses was studied. The effect of sal
t stress on growth as well as on polyamine (putrescine, spermidine and
spermine) and amino acid contents of the treated calluses was determi
ned. Enzymatic activities of the polyamine biosynthetic enzymes argini
ne and ornithine decarboxylase were also analyzed. A significant decre
ase in the growth of calluses in relation to increased salt concentrat
ions and to the tolerance of the callus was observed. Embryogenic Ariz
ona calluses showed the lowest growth inhibition and W64Ao2 calluses t
he highest inhibition after GO days of culture in saline medium. WpA c
alluses showed an intermediate response. At high-salt concentrations (
1.2-2.0 %), calluses showed a significant increase in total polyamine
content, especially caused by a rise in putrescine. This increase was
proportionally higher for Arizona and WpA than for W64 calluses. Where
as the spermidine content of Arizona calluses was augmented with salt,
a spermidine decrease was observed for W64 from 0.8 % NaCl. Arginine
decarboxylase activity increased from 1.2 to 2.0 % NaCl for Arizona ca
lluses, while in W64 calluses this increase was lower than in Arizona
up to 2.0 %. With respect to free amino acid contents, the levels of f
ree proline, which represent 50 % of the total free amino acid content
, decreased with increasing salt in the medium. The highest amino acid
increases were observed for arginine, alanine, glutamine, glutamic ac
id and gamma-aminobutyric acid. Arginine decarboxylase activity showed
significant increments in relation to salt stress, which may be relat
ed to putrescine and some amino acid variations. Relationships between
all the analyzed parameters and the polyamine synthesis and degradati
on processes under stress conditions are discussed.