Sodininkystė ir daržininkystė - Sodininkystės ir daržininkystės institutas

SCIENTIFIC WORKS OF THE LITHUANIAN INSTITUTE OFHORTICULTURE AND LITHUANIAN UNIVERSITY OF AGRICULTURE.SODININKYSTË IR DARÞININKYSTË. 2006. 25(1). 170-176.THE RESPONSE OF RADISH PHYTOHORMONESYSTEM TO OZONE STRESSAkvilë URBONAVIÈIÛTË, Raimonda ULINSKAITË,Giedrë SAMUOLIENË, Jurga SAKALAUSKAITË,Povilas DUCHOVSKIS, Aušra BRAZAITYTË,Jûratë Bronë ÐIKÐNIANIENË, Gintarë ÐABAJEVIENË,Kæstutis BARANAUSKISLithuanian Institute of Horticulture, LT-54333, Babtai, Kauno distr.E-mail: A.Urbonaviciute@lsdi.ltExperiments were performed at the Lithuanian Institute of Horticulture, Phytotroncomplex in 2005. The object of this study was to evaluate the effect of different ozoneconcentrations on phytohormone system in radish (Raphanus sativus L., cv. Þara) leaves.The exposure of 80, 160, and 240 µg m -3 ozone concentrations was maintained for sevendays. Day/night temperature was 21°C/17°C, photoperiod – 16 h. Phytohormones(gibberellic acid, zeatin, indolyl-3-acetic acid and abscisic acid) content analysis wasperformed using chromatographic method. Phytohormone balance is a suitable indicatorof the elevated ozone impact on physiological processes. These plant hormones do notact independently in response to ozone, but rather in a complex signaling network.According to phytohormone contents, radish under 160 µg m -3 treatment experiencedthe highest stress. The increase in phytohormones (zeatin, indolyl-3-acetic acid andabscisic acid) level after two weeks regeneration period is associated with the reactionof compensatory mechanisms and the regeneration of plant organs.Key words: phytohormones, radish, ozone.Introduction. Ozone is one of the major air pollutants, formed introposphere by the interaction of hydrocarbons, nitrogen oxides and sunlight,causing physiological damage to plants (Sandermann, 1996; Lin et al., 2001;Baier et al., 2005). It can reduce quantum yield, electron transport ofphotosystem II, membrane permeability, stomatal conductance, the functionof enzymes for CO 2fixation and photosynthesis (Lin et al., 2001), affectinteractions with plant parasites and change responses to pollutant mixtures(Sanderamann, 1996). Initially, the damage may be caused by reactive oxygenspecies (ROS) and hydrogen peroxide, released by ozone attack on apoplasticstructures (Lin et al., 2001; Conklin et al., 2004). Generally, ROS formedduring ozone exposure activate ethylene, salicylic acid (SA), abscisic acid170