Abstract

Atmospheric CO₂ concentrations are increasing and studies about the impact on plant species’ responses are on the rise. Unfortunately the wide range of variations in the published data is a concern when it comes to usefulness and application. Simple descriptive analyses on the published results are needed to make sense of the overall trends in plant responses to CO₂ enrichment. In the present report, 90 articles were the basis of a 395-entry database analyzed for general trends on how terrestrial plant species were reported to have responded to CO₂ fertilization.  The CO₂ concentrations that were studied range between 440 ppm and 900 ppm. The results revealed that 238 and 40 entries dealt with C3 and C4 pathways; respectively. A significant regression analysis (P=0.111), between CO₂ levels and average response, was detected for C3 plant species only. This highlights the need for more studies on C4 plants which constitute an important component of primary productivity on terrestrial ecosystems. Of the total entries into the database C4 plants had the highest average magnitude of response (27.1±0.4%).  At the functional group level, woody species were reported to have the highest average response (33.5±0.4%). Salinity, nutrient, defoliation and water stresses had average responses of 15.7±0.2, 12.3±0.3, 10.80±0.2 and 7.6±0.2%, respectively. In short, the above simplistic descriptive approach places much of what was studied in relation to plant responses to CO₂ fertilization into a practical perspective. Furthermore, detailed periodic analyses, including meta-analyses, are therefore highly recommended in order to summarize the body of published data, suggest up-to-date interpretations and make it available for practical use.

Key words:  Stress, CO₂, floral response.