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-deficient and manganese-sufficient needles of field-grown Norway spruce trees (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 an acidic pI less-than-or-equal-to 3, were identified using guaiacol or coniferylalcohol as substrates for activity staining after isoelectric focusing in a pH gradient from 3 to 9. The acidic peroxidases were capable of Mn-dependent NADH oxidation and H2O2 formation. Syringaldazine peroxidase activity was not found in apoplastic extracts, but was present in whole-needle extracts. Manganese deficiency did not affect the activity or the isoelectric focusing pattern (pH 3 to 9) of the apoplastic peroxidases. Soluble peroxidase activities from whole-needle extracts were significantly higher in Mn-deficient than in Mn-sufficient needles with all substrates tested. Mn-deficient needles contained slightly less cell wall material than Mn-sufficient needles, but the lignin content was similar. Neither apoplastic peroxidase activity nor lignification was affected by Mn deficiency, suggesting that apoplastic peroxidases are regulated independently from symplastic peroxidases.