Effects of Elevated CO2 Concentration on Phenotypic, Physiological and Biochemical Characteristics of Submersed Plant Potamogeton crispus Leaf

Abstract

The effects of elevated CO 2 concentration on growth and development of terrestrial plants have been studied intensively, but less scientific interest h as been raised on aquatic plants. In this study, a greenhouse experiment with su bmersed species Potamogeton crispus, one of dominant species in lakes along Yangtze River Basin, was studied comparatively in higher (1 000±50 μmol·mo l -1 ) and ambient (about 380 μmol·mol -1 ) CO 2 concentration to t e st whether CO 2 has significant impacts on phenotypic and some physiological an d biochemical characteristics as main effect. In addition, allometric analysis w as applied to distinguish whether phenotypic changes such as total leaf area are induced by environment (plastic) or plant size dependent (non_plastic). The res ults showed that phenotypic characteristics of P. crispus leaf in elevated C O 2 concentration changed significantly compared with that in ambient CO 2 concent ration. Leaf shape was more stubby, but leaf width, single leaf area, total leaf area per plant and leaf area ratio increased significantly in elevated CO 2 co ncentr ation. However, specific leaf area and leaf length did not differ between treatm ents. Total leaf area per plant was closely correlated with plant weight, indica ting that change in this phenotypic characteristic may depend on plant size. The result of allometric analysis certified that this change was a non_plastic resp onse, but plant size dependent. In addition, higher CO 2 concentration led to t he changes in pigment concentration. Chlorophyl a, chlorophyl b, total chlorophyl, carotenoid concentration and the ratio of chlorophyl a/b decreased in elevated CO 2 concentration. The soluble sugar concentration increased, but protein, N a nd P content decreased under higher CO 2 condition. It is concluded that elevated a tmospheric CO 2 concentration results in significant changes in some physiologi ca l and biochemical characteristics, especially increase of soluble sugar concentr ation, but not necessary in leaf phenotype. Maybe true adjustment in leaf ph enotype is under strong genetic rather than CO 2 control.