Inhibition of Apoplastic and Symplastic Peroxidase Activity from Norway Spruce by the Photooxidant Hydroxymethyl Hydroperoxide

Abstract

Young, clonal Norway spruce trees (Picea abies 1.) were exposed for 2 years at high altitudes to ambient atmospheric concentrations of photooxidants containing hydroxymethyl hydroperoxide (HMHP) as an important constituent. In spruce needles from a site with higher concentrations of organic peroxides in air, the apoplastic peroxidase activities were significantly lower than in needles exposed to lower organic peroxide concentrations. Cuaiacol peroxidase activities in total needle extracts were not affected. It has also been detected in leaves of isoprene-emitting plants after ozone fumigation (Hewitt et al., 1990). Therefore, it was suggested that this compound might be involved in mediating air pollution damage to plants (Hewitt et al., 1990).Peroxidases are possible targets of HMHP. Marklund (1971) found that an acidic guaiacol peroxidase isolated from horseradish is rapidly and irreversibly inhibited by HMHP. The susceptibility of peroxidases to HMHP in plant species such as Norway spruce (Picea abies L.) that are suffering greatly from environmental pollution has not yet been studParts of this study were financially supported by the Bayerisches Staatsministerium fiir Landesentwicklung und Umweltfragen.* Corresponding author; fax 49-761-808349.ied. In spruce needles about 2 to 5% of total "nonspecific" guaiacol peroxidase activity is found in the apoplastic space (Polle et al., 1990). Ascorbate peroxidase activity is localized in the cytosol and in chloroplasts of plant cells (Asada, 1992) but not in apoplastic washing fluids of spruce needles (Polle et al., 1990). It is unknown whether the ascorbate-specific peroxidases, whose enzymic characteristics are different from the family of 'nonspecific" guaiacol peroxidases (Asada, 1992), are inactivated by HMHP.In the present study we investigated peroxidase activities in needles of clonal spruce trees exposed for 2 years at high altitudes to ambient atmospheric concentrations of photooxidants including HMHP. Since airborne hydrophilic pollutants enter the leaves predominantly via the stomata and have to cross the aqueous apoplastic space before they reach intracellular targets (Polle and Rennenberg, 1993), apoplastic peroxidase activities were also investigated. The effect of HMHP on ascorbate and guaiacol peroxidase activities was analyzed in vitro. The significance of ambient atmospheric HMHP concentrations for damage to plants is discussed on the basis of the present results. MATERIALS AND METHODS Preparation of HMHP Stock SolutionsIn aqueous solution HMHP is a product of H202 and formaldehyde according to the following equilibrium reaction:To produce stock solutions of HMHP, concentrated solutions of HzOZ (30%) and formaldehyde (37%) were mixed stoichiometrically and stirred for 12 h at room temperature. The concentrations of HMHP, H202, and formaldehyde in the resulting "HMHP stock solution" were slightly variable from batch to batch. Therefore, the composition of each freshly prepared HMHP solution was fluorimetrically analyzed according to Lazrus et al. ...

Apoplastic Peroxidases and Lignification in Needles of Norway Spruce (Picea abies L.)

“…4, a and b). The presence of these isoperoxidases in apoplastic washing fluids of mature spruce needles has been reported previously (Polle and Chakrabarti, 1994;Polle and Junkermann, 1994).…”

Emission of Volatile Organic Compounds from Ozone-Exposed Plants

“…Whether or not peroxides taken up from the atmosphere may act toxic was discussed by Polle and Junkermann (1994). The authors concluded that organic peroxides such as hydroxymethyl hydroperoxide (HMHP) produced in the boundary layer and taken up by the plants may affect peroxidase activity in the apoplast.…”

The global budgets of organic hydroperoxides for present and pre-industrial scenarios

“…They are strong oxidants like ozone, and have some toxic effects on plants by inactivation of enzymes, impairing metabolic processes, and blanching chlorophyll (Hewitt et al, 1990;Hewitt and Terry, 1992;Polle and Junkermann, 1994). Methyl hydroperoxide (CH 3 OOH), the most abundant organic hydroperoxide, has a longer lifetime of 2e3 days and is less soluble in water than hydrogen peroxide (H 2 O 2 ) (Cohan et al, 1999;Mari et al, 2000;Wang and Chen, 2006).…”