Nitrogen Nutrition Effect on Aeroponic Basil (Ocimum basilicum L.) Catalase and Lipid Peroxidation

Considering the physiological importance of nitrogen (N) for the plant growth and its controversial role in the plant oxidative status, the objective of this research was to investigate the effect of three different N nutrition solution concentrations (1.8, 3.6 and 11.5 mM) on leaf and root oxidative stress of aeroponically cultured basil (Ocimum basilicum 14 plants. Catalase (CAT) activity and lipid peroxidation (LP) were used as oxidative stress indexes at two different growth stages (10 and 15 week-old plants respectively). Leaf and loot CAT activity was enhanced by the increment of N concentration at both growth stages of the plants. Especially in younger, high N nourished plants, 130 and 149% increments of the leaf and root CAT activities were observed respectively, in comparison with the low N nourished ones. Moreover, the root enzyme seems to be a bifunctional catalase-peroxidase considering its insensitivity to aminotriazole. On the other hand, root LP seems to be unaffected at thus N concentration range whereas leaf LP was enhanced at high N levels, especially in younger plants. These results suggest that increased N nutrition induces oxidative stress mainly in the leaves of aeroponically grown basil plants while the increase of CAT activity probably represents a part of plant's antioxidative defense against potent cellular damage similar to membrane lipid peroxidation.