Interpopulational variation in the flavonoid composition of Cistus ladanifer L. exudate

A study was made in different populations of Cistus ladanifer of the quantitative and qualitative variation of the exudate of the leaves and stems, including the exudate's aglycone flavonoid content. Two groups of populations were established according to different climate conditions, and the results showed the existence of interpopulational variability both quantitatively and qualitatively. The populations subject to the greatest thermal stress and moisture stress (Group I) synthesized more exudate and total flavonoids. The amounts of the different flavonoids synthesized also differed between the two groups of populations: Group I secreted more 3-O-methylkaempferol, 3,4′-di-O-methylkaempferol and 3,7-di-O-methylkaempferol and Group II more 4′-O-methylapigenin. Quantifying the proportion of each apigenin and kaempferol relative to their totals, it was observed that the synthesis of position 7 methylated flavonoids are enhanced in Group I, and position 4′ methylated flavonoids in Group II. The indication is that the climatic conditions to which a population of C. ladanifer is subject may lead to diversification in the flavonoid composition of the leaf and stem exudate, with the implication that flavonoids could have various ecological functions in this species.