Impacts of simulated drought stress and artificial damage on concentrations of flavonoids in Jatropha curcas (L.), a biofuel shrub.

We studied the possible roles of flavonoids in the antioxidant and antiherbivore chemistry in Jatropha curcas (L.), a Latin American shrub that holds great potential as a source of biofuel. Changes in flavonoid concentrations in the leaves of J. curcas seedlings exposed to artificial damage and to different rainfall patterns were assessed by applying a 32-factorial experiment in a greenhouse. The concentrations of different flavonoids in the leaves of seedlings were significantly affected by interaction effects of artificial damage, drought stress and age of the seedling. The highest flavonoid concentrations were obtained in seedlings imposed to the highest percentage of artificial damage (50 %) and grown under extreme drought stress (200 mm year-1). In this treatment combination, flavonoid concentrations were three-fold as compared to seedlings exposed to the same level of artificial damage but grown in 1900 mm year-1 rainfall application. Without artificial damage, the concentration of flavonoids in the seedlings grown in 200 mm year-1 rainfall application was still two-fold compared to seedlings grown in higher (>800 mm year-1) rainfall applications. Thus, the observed flavonoid concentration patterns in the leaves of J. curcas seedlings were primarily triggered by drought stress and light rather than by artificial damage, suggesting that drought causes oxidative stress in J. curcas.