Co <sub> 2 </ Sub> Control Of Tissue Culture Micro-ecological Environment

In order to study the functions of CO₂ in tissue culture, and to search the feasibility of the culture without (with low) sucrose in vitro conditions, a CO₂ real-time control system (RTCS) was developed. The RTCS is composed of a growth chamber, PC system, control devices, and gas resource assembles. Addi- tionally a realtime control software was designed. Using this system, the required ranges of CO₂ concentration can be obtained, and plantlets can be cultured under sucrose-free, CO₂ enrichment, a high photosynthetic photon flux, and non-aseptic conditions. The CO₂ concentrations in the traditional culture method (TCM) were measured, and the trending curve of the CO₂ concentrations in the whole day was also simulated. The result showed that plantlets cultured with TCM present strong power of photosynthesis, the CO₂ concentration in the little glass bottle reduced to the compensation point rapidly (less than one hour) after lighting. And since then, piantlets were very insufficient of CO₂ in the whole photoperiod. Under the conditions of 65 LI mol rn?s?photosynthetic photon flux density (PPFD, sidewd), 43 Lt mci m2 s?PPFD (upward), 12 Li mci m2 sPFD (down- ward) and 25t in the 12h?photoperiod every day, 20 to 30 days?growth of sub- cultured grape (cabernet sauvignon) plantlets under RTCS, controlling CO₂ con- centration ranges (600ppm 000ppm,SOOppm-1 000ppm, 1 000ppm. 500ppm), was compared with TCM (non-CO₂ enrichment) for three times, each without and with sucrose(lOg/l) in medium. The experiments showed that the average leaf dimension of plantlets micropropagated photoautotrophically (sucrose-free) and photomixotrophically (with sucrose) under RTCS with CO₂ enrichment increased by 90.0% and 140.90/a respectively, the average diameter of stems increased by 76.6% and 79.1%, and the average length of stems increased by 62.S% and 44.2%. Similarly, those under the TCM were 53.8% and 197.1%, 1.6% and 39.1%, 30.2% and 100.3% respectively. The dry weight of the plantlets cultured with sucrose under RTCS was 1.7 times and 6.6 times greater than that cultured without sucrose under RTCS and TCM respectively, and was 2.8 times greater than that cultured with sucrose under TCM. It is clear that the plantlets cultured under RTCS, especially those cultured with sucrose, had significantly stockier stems and shorter neighboring nodes distance, healthier roots and greater dry weight, which arc preferred characteristics of micropropaguted plantlets for ac- climatization to cx vitro conditions. Simultaneously, it was concluded from ob- serving the slices of stems that plantlets cultured under RTCS bad grown at more advanced stage. The results indicate that the RTCS is feasible to culture for plantlets without sucrose (photoautotmphy). Compared with TCM, the sucrose-free (sucrose- containing) culture with CO₂ enrichment embodied the significant superiority.