Growth, Plant Quality, and Survival of Sweet Cherry (Prunus avium L.) Seedlings are Enhanced by CO2 Enrichment

Enrichment with CO2 and a commercial mix of plant growth regulators were tested to improve the plant quality and survival of pregerminated cherry tree seedlings. Pregerminated seeds were transferred from a cold chamber to a climatic chamber where the CO2 was set at 800 mu mol.mol(-1) CO2 or at the ambient CO2 concentration. Also, half of the plants were sprayed with the mix of plant growth regulators and disposed randomly. The experiment lasted 18 days and physiological measurements, such as plant physiological status and growth, number of leaves, net CO2 assimilation (A(CO2)), internal CO2, stomatal conductance, and transpiration, were taken every 4 days. Also, at the end of the experiment, other parameters-such as total leaf area, photosynthetic pigments, soluble sugars, and starch-were recorded or quantified. During the experiment, plants cultured under CO2 enrichment exhibited a rapid increase in their photosynthetic rates, height, and leaf number; the commercial mix also increased plant height but inhibited leaf expansion and growth. At the end of the experiment, the amounts of starch and soluble sugars had increased in the plants grown under elevated CO2, compared with those plants grown in control conditions or with the commercial mix. Thus, culture at elevated CO2 achieved higher percentages of plant survival and of plants in active growth. We suggest that CO2 plays an important role-by increasing A(CO2), water use efficiency, soluble sugars, and starch-which results in plants that are physiologically more prepared for transfer to the field.