Submitted to: Hortechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 1997
Publication Date: N/A
Interpretive Summary: Carbon dioxide (CO2) is the major bi-product of alcohol fuel fermentations. In addition, carbon dioxide gas build-up has been associated with global warming. This work addresses how the utilization of low value gas generated by fermentation can be constructively developed into a value added product. Currently, the plant tissue culture/nursery industry produces over 100 million plants/year. Methods that improve growth and multiplication rates are needed by this industry. Normally, CO2 is employed in commercial greenhouses at a level of 1,000 to 1,500 ppm. In this study, we found that plant tissue cultures can readily use CO2 at levels of 10,000 to 50,000 ppm (about 10 to 50 x the levels normally thought useful to grow plants). Plants grown under these conditions were found to exhibit as much as a 10-fold increase in growth. Application of these techniques greatly improves growth rates of plants grown in sterile culture and create a ready-made market for CO2.
Technical Abstract: A continuous CO2 flow system was employed to study the growth of carrot (Daucus carota L.), citrus (Citrus macrophylla L.), kale (Brassica oleracea L.), lettuce (Lactuca sativa L.), radish (Raphanus sativus L.), and tomato (Lycopersicum esculentum L.) cultures in vitro under photoautotrophic, photomixotrophic, and heterotrophic conditions. Lettuce plantlets were grown on Murashige and Skoog medium with 0, 0.3, 1. and 3% sucrose within flow chambers containing 350, 750, 1,500, 3,000, 10,000, 30,000, and 50,000 uliter**-1 CO2. Increasing the levels of CO2, especially at the ultra-high levels (i.e., >3,000 uL liter**-1 CO2), increased fresh weight, shoot length, leaf number, leaf length, leaf width, root number, and root length for plantlets grown regardless of sucrose levels tested compared to plantlets grown at normal atmospheric CO2 levels, i.e., 350 uL liter**-1. For example, fresh weights of lettuce plantlets grown on medium containing 0 or 3% sucrose increased 11- and 13-fold, respectively, when supplemented with 30,000 uL liter**-1 CO2 compared to growth of lettuce plantlets grown on the same media without CO2 enrichment. Similar fold increases in growth responses were obtained with carrot, citrus, kale, radish, and tomato plantlets grown in atmospheres enriched with high CO2 levels, elevated from 3000 to 30,000 uL liter**-1. Optimum CO2 concentration varied among species suggesting a species-related response. Varying the rate of CO2 application between 250, 500, 1,500, 2,000 ml min**-1 did not effect the rate of growth of lettuce plantlets. The passive diffusion continuous flow through system presented in this paper is inexpensive, easily constructed, and allows for testing ultra-high CO2 levels on plant culture growth in vitro.