Article,
Elevated CO2 concentration, nitrogen use, and seed production in annual plants
Global Change Biology, 13 (10): 2161--2170 (Oct 1, 2007)
DOI: 10.1111/j.1365-2486.2007.01429.x
Abstract
Elevated atmospheric CO2 concentration (CO2) stimulates seed mass production in many species, but the extent of stimulation shows large variation among species. We examined (1) whether seed production is enhanced more in species with lower seed nitrogen concentrations, and (2) whether seed production is enhanced by elevated CO2 when the plant uses more N for seed production. We grew 11 annuals in open top chambers that have different CO2 conditions (ambient: 370 μmol mol−1, elevated: 700 μmol mol−1). Elevated CO2 significantly increased seed production in six out of 11 species with a large interspecific variation (0.84–2.12, elevated/ambient CO2). Seed nitrogen concentration was not correlated with the enhancement of seed production by elevated CO2. The enhancement of seed production was strongly correlated with the enhancement of seed nitrogen per plant caused by increased N acquisition during the reproductive period. In particular, legume species tended to acquire more N and produced more seeds at elevated CO2 than non-nitrogen fixing species. Elevated CO2 little affected seed N in all species. We conclude that seed production is limited primarily by nitrogen availability and will be enhanced by elevated CO2 only when the plant is able to increase nitrogen acquisition.
