Submitted to: American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: July 25, 2001
Publication Date: N/A
Technical Abstract: Although oxygen (O2) is an essential element for plant growth and metabolism, little research has been conducted to determine the influence of various O2 concentrations on growth (fresh weight), morphogenesis (leaves, roots, and shoots), and secondary metabolites. Mint (Mentha sp. L.) and thyme (Thymus vulgaris L.) shoots were cultured under 5, 10, 21, 32, or 43% O2 employing either 350 or 10,000 uL CO2 liter**-1. Shoots wer grown in vitro on Murashige and Skoog salts, 3% sucrose, and 0.8% agar employing 180 umoles.s**-1.m**-2 PPFD 16 hr photoperiod. Growth and morphogenesis responses varied considerably among the two plant species tested depending on the level of O2 administered. Nevertheless, growth was enhanced considerably for shoots under all O2 levels tested with 10,000 uL CO2 liter**-1 when compared to growth responses obtained from cultures grown on the same O2 levels with 350 uL CO2 liter**-1. Mint shoots did not texhibit any difference in growth and morphogenesis regardless of the O2 level tested with 10,000 uL CO2 liter**-1. In contrast, thyme shoots exhibited enhanced growth and morphogenesis when cultured in >21% O2 compared to shoots cultured under lower O2 levels. Essential oil compositions (i.e., the monoterpene, piperitenone oxide from mint and the aromatic phenol, thymol from thyme) were analyzed by CH2Cl2 extracts via gas chromatography from the shoot portion of plants grown in all O2 levels. Highest levels of thymol were produced from thyme shoots cultured under 15 and 21% O2 with 10,000 uL CO2 liter**-1 and were considerably less from shoots when grown under either lower or higher O2 levels. Highest levels of piperitenone oxide were obtained from mint cultures when grown with >21% O2 with 10,000 uL CO2 liter**-1.