Malondialdehyde cannot be related to lipoperoxidation in habituated sugarbeet plant cells

Malondialdehyde (TBARS: thiobarbituric acid reactive substances) has been investigated in non-organogenic and organogenic habituated and normal sugarbeet cell lines and compared with lipid hydroperoxides, conjugated diene formation and lipoxygenase activity in order to estimate the reality of lipid peroxidation processes which have been postulated in the habituated non-organogenic cell line. The results presented here exhibit a strong discrepancy between TBARS and the other indices tested. Neither hydroperoxide index, nor conjugated dienes, nor lipoxygenase activity could confirm that the non-organogenic habituated cells studied were submitted to permanent stress due to free radical attacks. Moreover, these results underlined that the use of TBARS to estimate lipid peroxidation must be considered with extreme caution in plants and can lead to misinterpretations.