Several ecological, genetic, and environmental factors are known to influence tannin concentration in plant tissues. In this study, the effects of seasonality, water availability, and sex of the plant on tannin concentration in the dioecious shrub Baccharis dracunculifolia were assessed. The effects of water availability on plant shoot growth and its relationship to tannin concentration were also experimentally evaluated. Tannins occurred in B. dracunculifolia from November to May, peaking during the summer (December to March). However, no relationship between tannin concentration, rainfall and temperature was found. No difference in tannin concentration and shoot growth was found between plants in the irrigated and control treatments, this suggesting that tannin production was affected by factors other than water availability, such as light intensity or plant phenology. There was a negative relationship between tannin concentration and shoot growth, possibly due to a trade-off between these metabolic activities. Plant gender did not influence tannin concentration and shoot growth, indicating that B. dracunculifolia did not show a differential resource allocation between male and female individuals.
tannins; Baccharis dracunculifolia; irrigation; gender; phenology