Turkish Journal of Botany




Studies were undertaken for induction of resistance against acute ozone exposure in Rhinacanthus nasutus (L.) Kurz. plants using ozone. Callus induced from Rhinacanthus nasutus leaf explants on Murashige & Skoog's (MS) medium supplemented with 3.40 µM of 2,4-dichlorophenoxy acetic acid (2,4-D) were treated with different concentrations of ozone (T_1 = 1.0 µmol mol^{-1} (±0.2), T_2 = 1.5 µmol mol^{-1} (±0.2), T_3 = 2.0 µmol mol^{-1} (±0.2)), and for the control (C) filtered air was supplied. Regeneration of shoots was obtained by culturing ozone-treated calli on MS medium supplemented with 5.57 µM of kinetin (KIN) and 1.30 µM of gibberellic acid (GA3). The frequency of regeneration of shoots from the callus was T_1 = 60%, T_2 = 49%, T_3 = 32%, but for the control 81% regeneration was obtained. Regenerated shoots were rooted in half-strength MS medium containing 4.92 µM of indole-3 butyric acid (IBA) and successfully acclimatised. The seedlings regenerated from ozone treated calli are referred to as T_1, T_2 and T_3 seedlings and the seedlings regenerated from filtered air-treated callus are referred to as control seedlings. T_1 seedlings hold remarkably more total soluble phenol content than T_2 and T_3 compared to the control seedlings. T_1 seedlings developed more resistance to withstand acute ozone exposure by increased phenylalanine ammonia-lyase activity and possessed more chlorophyll pigments and decreased H_2O_2 content relative to T_2 and T_3 seedlings compared to control seedlings.


Callus, chlorophyll, soluble phenol, phenylalanine ammonia-lyase (PAL)

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