K. Lesko et al., Effect of cadmium and titanium-ascorbate stress on biologically active compounds in wheat seedlings, NOVENYTERME, 50(1), 2001, pp. 71-81
The harmful processes caused by heavy metals are serious problems not only
for useful plants but, if they enter the food chain, for consumers as well.
This is why it is essential to clarify biochemical processes.
The effect of cadmium and combined cadmium and titanium-ascorbate was exami
ned on wheat seedlings (Triticum aestivum L.). The one-week-old hydroponica
lly-grown seedlings of wheat were exposed to Cd2+ (10(-7) M, 10(-3) M) and
Cd2+(10(-7) M, 10-3 M) + titanium-ascorbate (5 ng/cm(3)) stresses. The stre
ss effects were followed by changes in the free amino acid and polyamine co
ntents and the peroxidase enzyme activity in roots and shoots.
The free amino acid content was determined by ion-exchange liquid chromatog
raphy. The polyamine content was identified by OPLC (over-pressured layer c
hromatography). Peroxydase activity (U/mg protein) was measured by the spec
trophotometric method.
The results showed significant differences between the two plant organs (ro
ot and shoot) with respect to the biochemical response to the applied stres
s.
The total free amino acid content of the shoot samples was higher than that
of the roots. Cadmium treatment at the higher concentration caused the hig
hest accumulation of total amino acid content in both the shoots and roots.
Among the amino acids the threonine, scrine+ (Scr+Asn+Gln), glutamic acid,
proline, alanine, valine, isoleucine, leucine, histidine, lysine and argin
ine concentrations showed the most significant changes.
The different effects of cadmium and the combined cadmium+titanium-ascorbat
e treatment can be characterised based on the typical accumulation of polya
mines in the two organs of wheat seedlings. Agmatine accumulation was obser
ved in the control shoot sample while in the shoot sample treated with Cd2 (10-7 M) combined with titanium-ascorbate, putrescine tended to accumulate
. In the roots only putrescine increased significantly.
Peroxidase activity was more significant in the root samples than in the sh
oot samples. The highest peroxidase activity was measured in the ease of th
e Cd2+ (10(-3) M) treatment in the roots. Titanium-ascorbate treatment seem
ed to reduce the negative effects of heavy metal pollution in wheat seedlin
gs.
On the basis of the results it can be stated that the heavy metal stress ca
used typical biochemical changes in wheat seedlings. Further research is ne
eded to find out the relationship between the heavy metal stress and the ch
anges in free amino acid and polyamine contents as well as in peroxidase ac
tivity.