INFLUENCE OF BORON DEFICIENCY ON (CO2)-C-14 AND [U-C-14] SACCHAROSE INCORPORATION IN PRIMARY METABOLITES IN RELATION TO ESSENTIAL OIL ACCUMULATION IN MENTHA-PIPERITA

Under boron (B) deficiency, the CO2 exchange rate, chlorophyll (Chl) a nd oil contents significantly decreased, whereas Chl alb ratio, leaf a rea ratio and leaf stem ratio significantly increased. When B-deficien t plants had been supplied with the control solution for 3 weeks, ther e was a partial recovery in some growth and yield parameters. In leave s of deficient plants, (CO2)-C-14 incorporation in sugars, amino acids and organic acids decreased, whereas in stems the incorporation of th ese three fractions was higher than in the controls. Upon recovery (3 weeks) the patterns of (CO2)-C-14 incorporation in sugars, amino acids and organic acids in leaves and stems were similar to those in contro l plants. In leaves of the B-deficient plants, [U-C-14] saccharose inc orporation was very high with respect to controls and a major portion was in ethanol soluble fraction. The incorporation was significantly h igher in sugars and organic acids than in amino acids. A substantial p ortion of labelled saccharose remained in the stem and it was signific antly higher than in control plants. Under B-deficiency, the levels of primary metabolites and their partitioning between leaf and stem sign ificantly influenced the essential oil accumulation.