EFFECTS OF MANGANESE DEFICIENCY ON SOLUBLE APOPLASTIC PEROXIDASE-ACTIVITIES AND LIGNIN CONTENT IN NEEDLES OF NORWAY SPRUCE (PICEA-ABIES)

Apoplastic peroxidase activities were investigated in manganese-defici ent and manganese-sufficient needles of field-grown Norway spruce tree s (Picea abies L.). In Mn-sufficient needles, two sets of peroxidases, one with an alkaline pI greater-than-or-equal-to 9 and another with a n acidic pI less-than-or-equal-to 3, were identified using guaiacol or coniferylalcohol as substrates for activity staining after isoelectri c focusing in a pH gradient from 3 to 9. The acidic peroxidases were c apable of Mn-dependent NADH oxidation and H2O2 formation. Syringaldazi ne peroxidase activity was not found in apoplastic extracts, but was p resent in whole-needle extracts. Manganese deficiency did not affect t he activity or the isoelectric focusing pattern (pH 3 to 9) of the apo plastic peroxidases. Soluble peroxidase activities from whole-needle e xtracts were significantly higher in Mn-deficient than in Mn-sufficien t needles with all substrates tested. Mn-deficient needles contained s lightly less cell wall material than Mn-sufficient needles, but the li gnin content was similar. Neither apoplastic peroxidase activity nor l ignification was affected by Mn deficiency, suggesting that apoplastic peroxidases are regulated independently from symplastic peroxidases.