Enhanced growth of in vitro plants in photoautotrophic micropropagation with natural and forced ventilation systems

摘要

Recently, photoautotrophic micropropagation has been proved to be one of effective methods of lowering production costs in micropropagation by the reduction of biological contamination, the enhanced growth of in vitro plantlets, the increased percent survivals and elimination of acclimatization in the ex vitro stage. In naturally ventilated micropropagation, the air outside and inside the culture vessel exchanges through microporous membrane filters covering holes made on cap or upright sides of the culture vessel, or through a gas permeable material replacing the closure completely. In this system, several plant species, such as coffee, banana, Paulownia and sweetpotato, showed no significant difference in their growth when cultured under photoautotrophic conditions as compared with that under photomixotrophic conditions. Furthermore, the photoautotrophic growth of in vitro plantlets was significantly enhanced when air-porous supports, such as cellulose plug, vermiculite, Florialite (a mixture of vermiculite and cellulose fibers) or perlite were used instead of agar or gelrite. However, in large-scale production, the control and maintenance of gaseous components, especially carbon dioxide, in the headspace of culture vessels can not be achieved easily in naturally ventilated, small vessels. A forced ventilation system can help to control the ventilation rate and CO_2 concentration inside the culture vessel by means of airflow rate meter and CO_2 controller. This system may bring more benefits for large-scale micropropagation when large boxes/chambers are used. In case of coffee and sweetpotato, the growth of photoautotrophic plantlets was greater in forced ventilation system as compared with those in a natural ventilation system.