The 2012 ASHS Annual Conference

Plant responses to biotic and abiotic environmental stress conditions involve coordinated control of oxidant concentration in a variety of plant organelles.  Plants utilize the rapid production of reactive oxygen species (ROS) to limit penetration of biotic pathogens.  Hydrogen peroxide (H₂O₂) is the most stable and non-radical ROS.  Within cellular metabolism, H₂O₂ is produced when O₂^-· encounters protons in a reaction catalyzed by superoxide dismutase.  Superoxide radicals are a main product of the photo-reduction of O₂ within thylakoids, and subsequently become converted to H₂O₂.  Plant tissues can tolerate high concentrations of H₂O₂.  H₂O₂ also act as a signal molecule for coordinated plant growth and morphogenesis.  Studies have demonstrated the ability of to alleviate abiotic stress conditions through exogenous applications of H₂O₂; however, what remains unclear is the ability of use H₂O₂ to promote production of anti-oxidant compounds linked to nutritional quality in specialty vegetable crops.  The objective of this research was to induce production of anti-oxidant carotenoid phytochemicals in basil (Ocimum basilicum L.) through exogenous applications of H₂O₂.  ‘Genovese’ basil plants were grown in nutrient solution culture.  At 28 days after sowing, plants were exposed to daily applications of H₂O₂ at concentrations of 0.0; 0.1; 0.2; 0.4; 0.8; 1.6; and 3.2 mMol.  Basil shoot tissues were harvested after 6 days of treatment applications, freeze-dried, and measured for pigments and mineral elements.  There were significant decreases in shoot tissue and root tissue fresh mass with increasing H₂O₂ concentration in nutrient solutions.  Shoot tissue β-carotene, lutein, neoxanthin, total carotenoid pigments, chlorophyll a, chlorophyll b, and total chlorophyll pigments increased then decreased in response to increasing H₂O₂ concentrations.  Increasing H₂O₂ concentrations in nutrient solutions resulted in significant decreases in the shoot tissue elements of K, Mg, Cu, Mn, Mo, and Zn.  Data revealed the potential to increase anti-oxidant carotenoid pigments with proper H₂O₂ concentration management.  However, H₂O₂ applications resulted in negative impacts on plant biomass and the accumulation of essential tissue nutrients.