Abstract:

The effects of elevated CO2 concentration on growth and development of terrestrial plants have been studied intensively, but less scientific interest has been raised on aquatic plants. In this study, a greenhouse experiment with submersed species Potamogeton crispus, one of dominant species in lakes along Yangtze River Basin, was studied comparatively in higher (1 000±50 μmol·mol-1) and ambient （about 380 μmol·mol-1） CO2 concentration to tst whether CO2 has significant impacts on phenotypic and some physiological and biochemical characteristics as main effect. In addition, allometric analysis was applied to distinguish whether phenotypic changes such as total leaf area are induced by environment (plastic) or plant size dependent (non-plastic).The results showed that phenotypic characteristics of P. crispus leaf in elevated CO2 concentration changed significantly compared with that in ambient CO2 concentration. Leaf shape was more stubby, but leaf width, single leaf area, total leaf area per plant and leaf area ratio increased significantly in elevated CO2 concentration. However, specific leaf area and leaf length did not differ between treatments. Total leaf area per plant was closely correlated with plant weight, indicating that change in this phenotypic characteristic may depend on plant size. The result of allometric analysis certified that this change was a non-plastic response, but plant size dependent. In addition, higher CO2 concentration led to the changes in pigment concentration. Chlorophyl a, chlorophyl b, total chlorophyl, carotenoid concentration and the ratio of chlorophyl a/b decreased in elevated CO2 concentration. The soluble sugar concentration increased, but protein, N and P content decreased under higher CO2 condition. It is concluded that elevated atmospheric CO2 concentration results in significant changes in some physiological and biochemical characteristics, especially increase of soluble sugar concentration, but not necessary in leaf phenotype. Maybe “true” adjustment in leaf phenotype is under strong genetic rather than CO2 control.