Abstract:

A submerged clonal plant, Vallisneria spinulosa, was grown for three months in greenhouse under ambient CO2 (400±20) μmol·mol-1 and elevated CO2 (1000±50) μmol·mol-1 to test the dynamic change of its growth and nutrient accumulation during its life cycle. It is credible to estimate the biomass of the submerged macrophyte continuously by multiplex parameters of morphology without destroying the experimental material. The sprouting of turions had not been affected by elevated CO2. The growth rate of ortet above-ground responded positively to elevated CO2 during prophase and metaphase of life cycle, while the opposite result occurred during anaphase because much more photosynthetic substance transferred to blow-ground to reproduce turions under elevated CO2 condition. Both primary and secondary ramets had higher growth rate under elevated CO2 than under ambient CO2. There was no difference in C content of the same clonal modules under two experimental conditions. Elevated CO2 significantly stimulated P accumulation in all modules of V. spinulosa except turion compared with ambient CO2. However, due to bio-dilute resulted from quickly increasing biomass, a 12％ 14% of N content of leaf and turions reduced under elevated CO2, while no significant difference in root and rhizome under both CO2 concentrations was detected. Total C, N and P accumulated in submerged plant under elevated CO2 were much more than those under ambient CO2 because the growth rate of plant increased quickly under the former condition. It is concluded, therefore, from the present study that (i) elevated CO2 significantly stimulates V. spinulosa clonal growth which will be of great benefit to its competition with other species among the community; (ii) more carbon will sink in the water-ecosystem because aquatic plants biomass increases; (iii) the content of N、P will influence directly aquatic clonal plants’ growth in the global climate change.