The Relation Between Primary and Secondary Metabolism in Peppermint Under Fe-stress

Changes in growth, (U-14C) sucrose and 14CO2 incorporation in primary photosynthetic metabolic pool under Fe deficiency and recovery in relation to essential oil accumulation have been investigated in Mentha piperita grown in solution culture. In Fe deficiency, CO2 exchange rate, stomatal conductance, oil content, chlorophyll content and chlorophyll a/b (Chl a/b) were significantly affected. Growth data such as leaf area ratio, specific leaf weight, leaf weight ratio and leaf stem ratio indicate the leaf tissue to be more severely effected than stem. In Fe-deficient plants, total 14CO2 incorporation in the oil and primary metabolites significantly decreased. Incorporation of 14CO2 in sugars, amino acids and organic acids was significantly lower than for control plants. In stems, 14CO2 incorporation in amino acids and organic acids was significantly higher in Fe-deficient plants while the incorporation in sugars was similar to that found in control plants. In plants that have recovered from Fe deficiency the incorporation of 14CO2 into sugar fractions and oil was similar to that found in control plants. (U-14C) Sucrose incorporation in oil and various fractions is significantly higher in Fe-deficient plants. A significant portion of label was found to remain in the stems of deficient plants. Incorporation of (U-14C) sucrose is significantly higher in sugars, amino acid and organic acid fractions in leaves and in stems of Fe-deficient plants. The results suggest that under Fe deficiency the levels of primary photosynthetic metabolites, their partitioning between leaf and stem significantly influences essential oil accumulation in peppermint.