Abstract:

Plant reproductive traits are key characteristics for predicting the impacts of global changes on plant community, agro-ecosystem and plant ecological fitness. This review seeks to integrate current results about the effects of elevated CO₂ on plant reproductive traits in detail based on the existing experimental data in the past few decades. Earlier investigations demonstrate that elevated CO₂ advances the flowering time through increasing relative growth rate and accelerating developmental process. All the numbers of flowers, fruits, and seeds, the mass of seed as well as the production of pollen and nectar of plants have been found to be stimulated by CO₂ enrichment. It is further revealed that the increase in plant yields results largely from an increase in seed number rather than from individual seed mass. Elevated CO₂ concentrations have little effect on seed [N] of legumes, but significantly reduce seed [N] of most nonlegumes. Contents of proteins, amino acids, and some mineral ions usually decrease in seeds of most nonlegumes. Different functional groups of plants are often found to differ markedly in their reproductive responses to elevated CO₂: 1) crops allocate more mass to reproduction and produce more fruits and seeds than do undomesticated species; 2) indeterminate plants have stronger responses to elevated CO₂ in comparison with determinate species; 3) legumes are most responsive to elevated CO₂, followed by nonlegume C₃ species, then C₄ species. Based on the data available, it seems rational to believe that changes in plant reproductive traits resulting from elevated CO₂ may alter the competitive hierarchy, the species composition, and hence the functioning of plant community. Finally, some issues noteworthy for future researches in this field are also put forward with reference to the existing unsolved questions.

Key words: Elevated CO₂, Sexual reproduction, Plant responses, Seed quality, Reproductive traits