What was done
The authors transferred tobacco (Nicotiana tabacum L.) plantlets grown in vitro to ex vitro conditions for one month, during which time the plantlets were exposed to atmospheric CO2 concentrations of 330 and 1,000 ppm to study the effects of elevated CO2 on plantlet productivity following transfer to ex vitro conditions.

What was learned
Plantlets grown in elevated CO2 displayed rates of photosynthesis that were 189 and 72% greater than those displayed by ambiently-grown plants two and 28 days after transfer to ex vitro conditions, respectively.  This increase in photosynthesis led to greater growth rates and, ultimately, to significantly greater dry mass values for plantlets grown in elevated CO2.  In addition, CO2-enriched plantlets displayed no signs of photosynthetic acclimation after one-month exposure to 1,000 ppm CO2.  Although elevated CO2 had no effect on stomatal conductance, differences in leaf water content after detachment indicated that CO2-enriched plants had greater relative water contents and were less susceptible to wilting than control plants exposed to ambient air.  Furthermore, elevated CO2 caused significant increases in plant water-use efficiency.

What it means
As the air's CO2 content rises, it will likely allow a smoother transition from in vitro to ex vitro growing conditions for tobacco and perhaps other plantlets.  Elevated CO2 enhanced rates of photosynthesis and increased dry mass production, while simultaneously increasing internal plant water content and water-use efficiency, all of which phenomena would likely enhance plantlet acclimation to ex vitro conditions.