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3113241 
Journal Article 
No induction of polyamines and radical scavenging antioxidants in Nicotiana tabaccum exposed to iron excess, as investigated by the DPPH assay and differential spectroscopy 
Lovaas, E; Olsen, JE 
1998 
Yes 
Journal of Plant Physiology
ISSN: 0176-1617 
153 
3-4 
401-408 
WOS:000076688800018 
Recently it has been shown that Fe induces oxidative stress and antioxidant enzymes in Nicotiana tabaccum (Kampfenkel et al., 1995). Similarly it has been shown that polyamines are elevated by a number of stress factors (Galston and Kaur-Sawhney, 1995) and that polyamines are efficient antioxidants (Lovaas, 1996). In the present study we investigated whether Fe excess induces polyamines in Nicotiana tabaccum. We also screened for radical scavenging antioxidants (RSA) by the DPPH assay and for inducible compounds by differential UV spectroscopy. Effects of oxidative stress caused by Fe excess were studied in plants grown in hydroponic cultures in the presence of elevated Fe (100 mu mol/L), as compared with low levels (30 mu mol/L). Elevated Fe caused development of yellow-brown necrotic spots in the mature and old leaves, but not in young leaves. Apart from this no other effects of elevated Fe were observed. In particular we did not see any rise in polyamines, RSA or W-absorbing compounds as a result of the Fe treatment. However, striking qualitative and quantitative differences in antioxidant contents were found between different developmental stages of leaves. The young, healthy leaves contained high levels of polyamines. Mature leaves had high levels of radical scavenging antioxidants and a high content of a UV-absorbing substance, possibly a flavonoid that was absent in young leaves. We conclude that polyamines and radical scavenging antioxidants detected by the DPPH assay are not induced by Fe-stress, or that the induction of such antioxidants is a slow process. Our results are consistent with the idea that polyamines protect against oxidative damage. 
antioxidants; iron Nicotiana tabaccum; polyamines; stress factors