Under boron (B) deficiency, the CO2 exchange rate, chloropliyll (Clil) and oil contents significantly decreased, whereas Clil alb ratio, leaf area ratio and leaf stem ratio significantly increased. When B-deficient plants had been siipplied witli tlie control solution for 3 weeks, there was a partial recoveiy in sonie growtli and yield parameters. In leaves of deficient plants, •^C02 incoiporation in sugars, ainino acids and organic acids decreased, whereas in stems the incoiporation of these three fractions was higher than in the Controls. Upon recovery (3 weeks) the pattenis of '‘*C02 incoiporation in sugars, amino acids and organic acids in leaves and stems were similar to those in conPol plants. In leaves of the B-deficient plants, [U-’‘*C] saccharose incoiporation was very high with respect to Controls, and a major portion was in ethanol soluble fraction. The incoiporation was significantly higher in sugars and organic acids than in amino acids. A substantial portion of labellcd saccharose remained in the stem and it was significantly higher than in control plants. Under B- deficiency, the levels of primaiy metabolites and their partitioiiiiig between leaf and stem significantly influenced the essential oil accumulation.