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Title: Elevated carbon dioxide levels enhance rosmarinic acid production in spearmint plantlets

Author
item Tisserat, Brent
item Berhow, Mark
item Vaughn, Steven

Submitted to: Book Chapter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2008
Publication Date: 2/20/2010
Citation: Tisserat, B., Berhow, M.A., Vaughn, S.F. 2010. Elevated carbon dioxide levels enhance rosmarinic acid production in spearmint plantlets. In: Gupta, V.K., Verma, A.K., Koul, S., editors. Utilisation and Management of Medicinal Plants. New Delhi: Daya Publishing House. p. 124-135.

Interpretive Summary: CO2 is an essential element necessary for plant growth yet little information about how CO2 atmospheres affects growth and secondary metabolism exists. We studied a broad range of CO2 atmospheric environments to ascertain the influence of CO2 on mint microshoots growth and secondary metabolism in order to develop a technique to commercially produce important phytochemicals in vitro. Mentha spicata L. (spearmint) a member of the Lamiaceae family, a widely cultivated herb, was employed in this study. Our results indicate that this mint grows well with a broad range of CO2 atmospheres. In addition, the rosmarinic acid, an important and high-dollar value diterpene, increases as the CO2 levels increase. This study verifies that high rosmarinic acid and biomass can occur simultaneously. Continued application of the techniques employed in this study may result in the commercial production of high dollar value pharmaceuticals and phytochemicals within a controlled in vitro system.

Technical Abstract: The C20 diterpene rosmarinic acid (RA) is synthesized in the phenylpropanoid pathway and is constitutively expressed in spearmint (Mentha spicata L.) plantlets grown in vitro. RA levels within plantlet leaves were found to be readily manipulated by the nutritional and physical environments. Higher RA levels, about a 100 % increase, occurred from plantlets cultured on a Murashige and Skoog media with 3% sucrose (BM) compared to plantlets on BM without sucrose. Plantlets were grown on BM under either 350 or 10,000 ul CO2 L-1 and subjected to various Photosynthetic photon flux density (PPFD) levels (34, 80, 120, and 180 umole..m-2.s-1) to determine the optimum light level to conduct experiments. The best light level was determined to be 120 umole..m-2.s-1 because it allowed for high growth and RA production. Spearmint shoots on BM were grown under 350, 1,500, 3,000, 10,000, or 30,000 ul CO2 L-1 for 8 wks. Generally, increasing levels of CO2 produced increased growth, morphogenesis and RA concentrations. Mint cv ‘557789’ plantlets produced about a five-fold increase in RA concentration over the control. High positive correlations occur between CO2 levels and spearmint plantlet growth (fresh weight), morphogenetic responses (leaves, roots and shoots) and secondary metabolism (RA).