Efekat apscisinske kiselime u odgovoru odabranih vrsta briofita na stres izazvan natrijum-hloridom

Abstract

Poznato je da briofite odgovaraju na povećane koncentracije NaCl i ABA na fiziološkom, biohemijskom i molekularnom nivou, iako je većina istraživanja bazirana na model vrsti Physcomitrella patens. U cilju ispitivanja efekata NaCl i ABA na halofitne vrste mahovina (Entosthodon hungaricus i Hennediella heimii) i definisanje razlika u odgovoru i otpornosti među njima, korišćene su različite biohemijske i histohemijske metode kojima su identifikovana i kvantifikovana jedinjenja, čije prisustvo može ukazati na njihovu ulogu u toleranciji na stres izazvan NaCl. ABA utiče na smanjenje koncentracije fotosintetičkih pigmenata, fenolnih jedinjenja, terpenoida i šećera. Međutim, kada se primeni kao predtretman, dovodi do povećanja preživljavanja održavajući koncentraciju primarnih i sekundarnih metabolita na umerenom nivou. Kvalitativni i kvantitativni sastav pojedinačnih komponenti je species-specifičan, što uslovljava različit odgovor na egzogeno dodat NaCl i ABA. Entosthodon hungaricus dominantno akumulira p-kumarinsku kiselinu i flavonoide, slično vrsti P. patens, dok H. heimii poseduje najveću koncentraciju terpenoida i flavonoida, ali ne i p-kumarinsku kiselinu. Šećeri su bitna komponenta kod sve tri vrste, mada se izomaltoza specifično nalazi kod brio-halofita tokom delovanja NaCl. Histohemijskim tehnikama je potvrđena akumulacija metabolita u protonemi, dok visoke koncentracije NaCl utiču na njihovu akumulaciju i u filoidima. ABA utiče na transpoziciju fenolnih jedinjenja u ćelijske zidove protoneme i filoida. Brio-halofite akumuliraju metabolite u većoj koncentraciji i odlikuje ih smanjena produkcija slobodnih radikala, što ukazuje da su one u velikoj meri prethodno pripremljene na stres izazvan sa NaCl i da ABA dodatno utiče na poboljšanje njihovog odgovora.

Bryophytes are known to respond to elevated NaCl concentrations and exogenous ABA at physiological, biochemical, and molecular levels, although most studies are based on model moss Physcomitrella patens. The aim of this research is to investigate the effects of NaCl and ABA on bryo-halophytes (Entosthodon hungaricus i Hennediella heimii) and to define the differences in their responses and resistance to salt stress using biochemical and histochemical analyses to identifiy and quantify compounds involved in tolerance to salt stress. Exogenous ABA leads to a decrease in the concentration of photosynthetic pigments, phenolic compounds, terpenoids, and sugars. When ABA was applied prior to salt stress, not only the survival rate, but also the concentration of primary and secondary metabolites increased. The qualitative and quantitative contents of metabolites are species-specific, indicatig different responses to exogenous NaCl and ABA. Entosthodon hungaricus accumulates p-coumaric acid and flavonoids, similarly to P. patens, while terpenoids and flavonoids are dominantly present in H. heimii, but not p-coumaric acid. Sugars are important constituents in all three studied species, although isomaltose may be a specific sugar in bryo-halophytes during salt stress. Histochemical analyses revealed an accumulation of metabolites in the protonema, while they can also be detected in phlloids upon elevated NaCl concentration. Exogenous ABA affects the conversion of phenolic compounds into cell walls of protonema and phylloids. Bryo-halophytes accumulate metabolites in greater concentration and produce smaller amount of free oxygen radicals, suggesting that they are to some extent prepared for salt stress, and that ABA pretreatment increases their response to stress.