RELATIVE IMPORTANCE OF GROWTH AND LIGHT LEVEL ON TERPENE CONTENT OF GINKGO-BILOBA

Growth of young Ginkgo biloba cultivated in a greenhouse, in natural light (varying between 125 and 1100-mu-E m-2 s-1), at 24-17-degrees and evolution of the terpene content (ginkgolides A, B, C, J and bilobalide) in leaves, shoots and roots were observed at the same moments during the first three years of life. Leaves accumulate more terpenes than roots and especially shoots. Annual mean concentrations of terpenes in leaves remain constant during the first three years of Ginkgo development, whereas those of roots and shoots evenly decrease. During one vegetative season, terpene content fluctuated significantly in leaves. This is mainly due to seasonal variations of ginkgolide A and bilobalide, which reach a maximum value at the end of summer or at the beginning of autumn. When the plants are cultivated in a climate chamber, in constant artificial light with medium photonic flux (250-mu-E m-2 s-1) at the same temperatures, the ginkgolide and bilobalide content in leaves remains low and constant. The level of terpene accumulation in G. biloba leaves may be linked to the photonic level and not to leaf or plant growth or to a specific stage of organs.