INFLUENCE OF BORON NUTRITION ON ESSENTIAL OIL BIOGENESIS, GLANDULAR SCALES, CO2 ASSIMILATION AND GROWTH IN MENTHA-ARVENSIS L

In Mentha arvensis L., boron supply between 0.5 to 1.0 g(B) m-3 was op timal for maximal shoot and root growth and essential oil yield per pl ant. There was no significant effect of B supply on the relative perce ntage of menthol, menthone and menthyl acetate in the oil. The incorpo ration of (U-C-14)saccharose into essential oil increased significantl y with increasing B supply. Co-feeding of B with labelled sucrose to B -deficient plants exhibited a similar patterns of incorporation. Frequ ency and size of oil glands, net photosynthetic rate, stomatal conduct ance, and the concentration of soluble sugars and micronutrients (Fe, Mn, Cu and Zn) were severely affected under excess boron.