EFFECT OF SALT STRESS ON ANTIOXIDANT DEFENCE
SYSTEM IN LENTIL (Lens culinaris M.) SEEDLINGS
Department of Biochemistry
Supervisor: Prof. Dr. Huseyin Avni Oktem
Co-Supervisor: Prof. Meral Yucel
2001, 100 pages
In this study changes in the activity of
antioxidant enzymes such as superoxide dismutase (SOD: EC 22.214.171.124),
catalase (CAT: EC 126.96.36.199), ascorbate peroxidase (APX: EC
188.8.131.52) and glutathione reductase (GR: EC 184.108.40.206), cell membrane
stability, lipid peroxidation in terms of malondialdehyde (MDA)
content, H2O2 content, proline content and physiological changes (as
wet-dry weights, root-shoot lengths) of 14 days old lentil (Lens
culinaris, Medik. cv. Sultan-1) seedlings subjected to 100 mM and
200 mM NaCl stress for 5 days were studied.
Four SOD isozymes were differentiated in lentil namely Cu/ZnSOD1,
Cu/ZnSOD2, FeSOD and MnSOD, FeSOD being only in leaves. Salinity
enhanced the activity of Cu/ZnSOD isozymes and the increase was much
higher in roots when compared to leaves. MnSOD activity increased
only at 200 mM NaCl stress while FeSOD activity decreased at both
stress concentrations. Total SOD activity enhanced in both tissues
but the increase was more pronounced in roots. APX and GR activity
was induced under both salt treatments however a slight decrease in
CAT activity was detected in both tissues.
Root-shoot lengths and wet-dry weights significantly decreased by
salt treatments. A higher level of lipid peroxidation (MDA content)
was observed in leaves when compared to roots at both NaCl stresses.
This finding was matched with electrolyte leakage test results in
which a significant increase was observed in leaves, while in roots
no change was detected.
Proline content increased in both tissues in correlation with
increased salt stress. A higher increase was observed in H2O2
content in leaves when compared to roots.
The results obtained suggest that leaves are more susceptible to
salt stress. In roots Cu/ZnSOD, APX and proline seem to play an
important role in defense against salt stress by effectively
removing reactive oxygen species.
Key words: Lentil, salt stress, oxidative stress, SOD, APX,
GR, CAT, proline, H2O2, lipid peroxidation, MDA.
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