Capsaicinoids, the chemical compounds that confer the pungency trait to peppers, are accumulated at different levels in all species of the genus Capsicum. There is much evidence suggesting that the synthesis of capsaicinoids occurs in the placenta interlocular septum of pepper fruits; however, the exact localization of the capsaicinoids biosynthesis accumulation pathways is still under debate. Thus, the aim of the present work was to evaluate whether pepper plants synthesize or accumulate capsaicinoids in vegetative organs as an indirect way to elucidate the systemic regulation of the capsaicinoid biosynthesis. For that purpose, we studied habanero pepper grown in the Yucatan Peninsula, which is among the hottest pepper worldwide. Our results, obtained by chromatographic and enzymatic measurements, provide solid evidence that habanero pepper plants do not accumulate capsaicinoids in the vegetative organs analyzed, even under water stress conditions. Thus, it is probable that the accumulation of capsaicinoids is restricted to reproductive organs.
The pungency of chili peppers is conferred by compounds called capsaicinoids that are produced only in the fruits of the Capsicum genus. Accumulation of capsaicinoids in these fruits may be affected by environmental conditions such as water and nutrient stresses, although these effects may vary even among genotypes within a species. The Habanero pepper (Capsicum chinense Jacq.), grown in the Yucatán, is in especially high demand as a result of its unique flavor, aroma, and pungency and is the second most important commercial crop in the state after the tomato. Although the Habanero pepper is a significant economic resource for the region, few studies have investigated the effects of abiotic stresses on capsaicinoid production. In this study, the effects of water stress on plant growth, capsaicinoid accumulation, and capsaicin synthase activity were evaluated. Habanero pepper plants under water stress had a lower height, root dry weight, and root/shoot relation than control plants, which were irrigated daily. However, fruit growth and production were unaffected by water stress. Capsaicin and dihydrocapsaicin concentrations increased in fruits of stressed plants compared with control plants, and this effect was correlated with fruit age. However, capsaicin synthase activity was reduced in response to water stress, and this effect depended on both stress severity and fruit age. These results provide new information on the regulation of capsaicinoid metabolism in response to abiotic stress from the fruit of a highly pungent chili pepper.