Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2001
Publication Date: 11/26/2001
Citation: TISSERAT, B., VAUGHN, S.F., SILMAN, R.W. INFLUENCE OF MODIFIED OXYGEN AND CARBON DIOXIDE ATMOSPHERES ON MINT AND THYME PLANT GROWN, MORPHOGENESIS, AND SECONDARY METABOLISM IN VITRO. PLANT CELL REPORTS. 2002. V. 20. P. 912-916. Interpretive Summary: Oxygen (O2) is one of the most important elements necessary to plant growth, yet little information about how O2 atmospheres affect plant growth exists. We studied a broad range of O2 and carbon dioxide (CO2) atmospheric environments to ascertain the influence of O2 on plant growth and secondary metabolism which can aid researchers in effectively employing goptimal physiological atmospheres in future biotechnological research. Tw species of Lamiaceae, thyme and mint, were employed in this study. Our results indicate that these plants can easily survive and grow well in a broad range of O2 atmospheres (i.e., 5 to 43% O2). However, secondary metabolites can vary considerably depending on the level of O2 tested. Our results did not always conform to observations in previously published articles as to the influence of O2 on secondary metabolism. This study illustrates that each plant species biochemical and growth responses should dbe empirically tested with a broad range of O2. This study suggests that O2 and CO2 atmospheric environments may greatly influence plant growth and metabolism and may provide systems to enhance the commercial production of important plant metabolites.
Technical Abstract: Growth (fresh weight) and morphogenesis (production of leaves, roots, and shoots) of mint (Mentha sp. L.) and thyme (Thymus vulgaris L.) shoots were determined under atmospheres of 5, 10, 21, 32, or 43% O2 with either 350 or 10,000 umol mol**-1 CO2. Plants were grown in vitro on Murashige and Skoog salts, 3% sucrose, and 0.8% agar employing a 16 hr/day, 180 umoles.s**-1.m**-2 16 hr photoperiod. Growth and morphogenesis responses varied considerably for the two plant species tested depending on the level of O2 administered. Growth was considerably enhanced for both species under all O2 levels tested when 10,000 umol mol**-1 CO2 was added as compared to growth responses obtained on the same O2 levels tested with 350 umol mol**-1 CO2. Mint shoots exhibited high growth and morphogenesis responses for all O2 levels tested with 10,000 umol mol**-1 CO2 included. In contrast, thyme shoots exhibited enhanced growth and morphogenesis when cultured in greater than or equal to 21% O2 with 10,000 umol mol**-1 CO2 included compared to shoots cultured under lower O2 levels. Essential oil composition (i.e., monoterpene, piperitenone oxide from mint and aromatic phenol, thymol from thyme) was analyzed from CH2Cl2 extracts via gas chromatography from the shoot portion of plants grown in all O2 levels. The highest levels of thymol were produced from thyme shoots cultured under 10 and 21% O2 with 10,000 umol**-1 CO2 and were considerably less from shoots when grown under either lower or higher O2 levels. High levels of piperitenone oxide were obtained from mint cultures grown under greater than or equal to 21% O2 with 10,000 umol mol**-1 CO2 compared to that obtained with lower O2 levels.