Capsaicin accumulation is related to nitrate content in placentas of habanero peppers (Capsicum chinense Jacq.)

BACKGROUND: The presence of capsaicin, the pungent principle of peppers, is restricted to the fruits of hot cultivars. This compound, which is produced in the fruits' placenta, requires 3 mol of nitrogen to be formed. Hence nitrogen availability may affect pepper pungency through its content in the fruit tissues. On the other hand, potassium may also affect pepper pungency given its positive effect on fruit development. In order to address this issue, plants of habanero pepper (Capsicum chinense Jacq.) were hydroponically cultured with various doses of nitrate and potassium and the contents of these ions and capsaicin were analyzed in the different fruit tissues. RESULTS: Treatments did not produce major effects on pod yield or size during the experimental period, and pepper pods from plants growing under low nitrate concentrations presented no significant differences in total nitrate content. However, lower nitrate, as well as low capsaicin contents, were found in the isolated placentas from peppers grown on the lowest nitrate doses. Variations in potassium availability resulted in differences in pod production per plant, but not in capsaicinoid accumulation. CONCLUSION: Under the assayed conditions, nitrate content in the placenta affects capsaicin synthesis.