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Effects of Elevated CO2 on the Reproduction and Progeny of a Dioecious Plant
Reference
Wang, X.  2005.  Reproduction and progeny of Silene latifolia (Caryophyllaceae) as affected by atmospheric CO2 concentration.  American Journal of Botany 92: 826-832.

What was done
The author grew well watered and fertilized specimens of white campion (Silene latifolia Poiret, a short-lived perennial herb of Eurasian origin that has been naturalized in North America) from seed to maturity in pots within controlled environment chambers that were maintained at mean CO2 concentrations of 386 and 696 ppm, while documenting various reproductive responses during growth and at final harvest, after which the seeds that had been produced by the plants in this experiment were used to grow a second generation of plants under the same environmental conditions in which the parent plants had been grown.

What was learned
In the first experiment, the total reproductive biomass of the plants that were grown in CO2-enriched air was 32% greater than that of the plants grown in ambient air, as was the total number of fruit produced.  In the second experiment, for seeds from female plants grown in ambient air, 55% of all emergence occurred within six days of sowing, while for seeds from plants grown in CO2-enriched air, 67% of total emergence occurred during the same period.  In addition, 87% of the seeds from the elevated-CO2-grown plants ultimately germinated, while only 67% of the seeds from the ambient-CO2-grown plants did so.  Last of all, there was a tendency for a greater percentage of female progeny to be produced in the CO2-enriched air than in ambient-air (56.3% vs. 52.7%).

What it means
The synergistic effect of a greater number of seeds being produced per female plant, a higher percentage of seed germination, and more female-biased seed production in CO2-enriched air would seem to suggest that white campion will fare well in a high-CO2 world of the future, which might cause some to worry, seeing it is a rather cosmopolitan and somewhat weedy species.  It must be remembered, however, that any plants of agricultural value with which it might compete will also be doing better in such a future world.  Hence, the greater importance of this study is what it may imply about other dioecious species, especially in light of the fact that Silene latifolia, in the words of Wang, "has become a model system for studying sexual dimorphism and sex-determination mechanisms and is likely the most extensively studied dioecious species."

Reviewed 27 July 2005