Volume 15, Number 31: 1 August 2012
Believing that anthropogenic-induced climate change will indeed "lead to an excessive change in climate conditions in greenhouses, particularly during the summer," Dannehl et al. (2012) developed what they call "a new climate strategy for greenhouses," which they designed "to avoid plant damages." This strategy consists of the combined application of "a high pressure fog system and CO2 enrichment that can be applied to decrease the inside temperature and to increase the levels of relative humidity and CO2 concentrations at a high ambient temperature."
These goals were accomplished while the five German researchers worked with tomatoes in two separate cabins of an experimental Venlo-type greenhouse at the Humboldt-Universitat zu Berlin, where the plants were grown under identical light conditions, but where one of the cabins utilized a DescFog system equipped with a high-pressure fog creation unit that produced very small (10µm) droplets of demineralized water above the plants and thus ensured a uniform evaporative cooling of them. Simultaneously, the CO2 concentration of the cabin air was set at 900 ppm from 5 to 11 am and at 700 ppm from 11 am to 6 pm in both cabins. So what were the "fruits" of their labor?
Dannehl et al. report that the changed microclimate in the cabin with the DescFog system was "sufficient to accelerate plant growth, to increase dry matter in leaves, and to promote the formation of fruit set per truss in comparison to [plants] grown under conventional climate conditions." In addition, they say that the new climate strategy "led to a maximum total yield increase by 20%, to a reduction of blossom-end rot in tomatoes and to a pronounced increase in fruit size during the spring experiments," and that "the climate conditions caused by the new technology significantly promoted secondary metabolism, resulting in a maximum increase in contents of lycopene (by 49%), ß-carotene (by 35%), and phenolic compounds (by 16%) as well as associated antioxidant activity in the water-insoluble (by 18.5%) and water-soluble (by 35.4%) fraction compared to the conventional treated plants," which group of enhancements, in their estimation, "most likely benefits human health."
We would only add, in this regard, that the increase in the air's CO2 content in both of the experimental cabins likely also increased the "baseline" values of these several beneficial plant compounds, as may readily be seen by perusing the several journal reviews we have written and archived in our Subject Index under the heading of Health Effects (CO2 - Health-Promoting Substances).
Sherwood, Keith and Craig Idso
Reference
Dannehl, D., Huber, C., Rocksch, T., Huyskens-Keil, S. and Schmidt, U. 2012. Interactions between changing climate conditions in a semi-closed greenhouse and plant development, fruit yield, and health-promoting plant compounds of tomatoes. Scientia Horticulturae 138: 235-243.