Influence of modified oxygen and carbon dioxide atmospheres on mint and thyme plant growth, morphogenesis and secondary metabolism in vitro

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% O 2 with either 350 or 10,000 µmol mol -1 CO 2 . Plants were grown in vitro on Murashige and Skoog salts, 3% sucrose and 0.8% agar under a 16/8-h (day/night) photoperiod with a light intensity of 180 µmol s -1 m -2 . Growth and morphogenesis responses varied considerably for the two plant species tested depending on the level of O 2 administered. Growth was considerably enhanced for both species under all O 2 levels tested when 10,000 µmol mol -1 CO 2 was added as compared to growth responses obtained at the same O 2 levels tested with 350 µmol mol -1 CO 2 . Mint shoots exhibited high growth and morphogenesis responses for all O 2 levels tested with 10,000 µmol mol -1 CO 2 . In contrast, thyme shoots exhibited enhanced growth and morphogenesis when cultured in ≥21% O 2 with 10,000 µmol mol -1 CO 2 included compared to shoots cultured under lower O 2 levels. Essential oil compositions (i.e. monoterpene, piperitenone oxide from mint and aromatic phenol, thymol from thyme) were analyzed from CH 2 Cl 2 extracts via gas chromatography from the shoot portion of plants grown at all O 2 levels. The highest levels of thymol were produced from thyme shoots cultured under 10% and 21% O 2 with 10,000 µmol mol -1 CO 2, and levels were considerably lower in shoots grown under either lower or higher O 2 levels. Higher levels of piperitenone oxide were obtained from mint cultures grown under ≥21% O 2 with 10,000 µmol mol -1 CO 2 compared to that obtained with lower O 2 levels.

Effects of Growth Regulators on Biomass and the Production of Secondary Metabolites in Peppermint (<i>Mentha pi-perita</i>) Micropropagated <i>in Vitro</i>

“…Such cultures lack the complex tissue and organ differentiation found in intact plants [10]. On the other hand, micropropagated plants, the normal sites of secondary metabolism in nature, easily produce commercially desirable secondary metabolites in vitro [8,10,11]. In the mint family (Labiatae), EOs are synthesized primarily in leaf epidermal cells and stored primarily in glandular leaf trichomes [12].…”

“…In the mint family (Labiatae), EOs are synthesized primarily in leaf epidermal cells and stored primarily in glandular leaf trichomes [12]. These glandular trichomes are present on the leaf surfaces of tissue culture plantlets and readily produce volatile Eos [11,13]. The effects of growth regulators on EO production are highly variable.…”

Tissue culture in synthetic atmospheres: diffusion rate effects on cytokinin-induced callus growth and isoflavonoid production in soybean [Glycine max (L.) Merr. cv. Acme]

“…The most likely explanation for the absence of an effect of gas diffusion rate in the daidzein assay is that differences in diffusion rates between argon, nitrogen, and helium do not change bioavailability of oxygen enough to be relevant to isoflavonoid metabolism. Tisserat et al (2002) noted that production of thymol in Thymus sativa (thyme) was not significantly different between cultured plants treated with 10% oxygen and those treated with ambient levels of oxygen when carbon dioxide was not limiting. They also noted that piperitenone oxide production in Mentha sp.…”

Growth, morphogenesis, and essential oil production in Mentha spicata L. plantlets in vitro

“…Cell suspensions and callus cultures lack the complex tissue and organ differentiation associated with plants and this probably contributes toward the lack of expression of certain metabolites (Curtin 1983;Charlwood et al 1990;HavkinFrankel et al 1997;Giri and Narasu 2000;Bourgaud et al 2001;Rao and Ravishankar 2002). In contrast, microroots and microshoots, which are the normal sites for secondary metabolism in nature, readily manifest commercially desired secondary metabolites in vitro (Charlwood et al 1990;Giri and Narasu 2000;Bourgaud et al 2001;Tisserat and Vaughn 2001;Rao and Ravishankar 2002;Tisserat et al 2002;Vanisree et al 2004). For example, in the mint family, essential oil synthesis occurs primarily in the leaf epidermal cells and storage primarily in glandular leaf trichomes (Shanker et al 1999;Hallahan 2000;Turner et al 2000).…”

“…For example, in the mint family, essential oil synthesis occurs primarily in the leaf epidermal cells and storage primarily in glandular leaf trichomes (Shanker et al 1999;Hallahan 2000;Turner et al 2000). Examination of the leaf surfaces of foliage from tissue culture plantlets also reveals the occurrence of these leaf trichomes (unpublished data) and they also readily produce volatile essential oils (Tisserat and Vaughn 2001;Tisserat et al 2002). A close relationship exists between primary metabolism of plantlets, which can be seen in growth and organ development and secondary metabolism, which is the production of specialized complex metabolites (Gulmon and Mooney 1986;Herms and Mattson 1992;Matyssek et al 2002).…”