Photosynthetic pigments and CO2- exchange of macrophytes in the middle taiga subzone

Data on the photosynthetic pigment content (chlorophylls and carotenoids) and CO2-gas exchange parameters of higher aquatic plants (macrophytes) from five reservoirs in the vicinity of Syktyvkar (the middle taiga subzone of the European Northeast) are given. The leaves of submerged macrophytes were characterized by low chlorophyll content and photosynthetic rates, were well adapted to low level of irradiance. The leaves of emergent plants accumulated more carotenoids (up to 2 mg/g of dry weight). Photosynthetic rates per dry mass in emergent leaves at photosaturation were higher (15 mg CO2 g-1 dw h-1) as compared to submerged plants. The positive relationships between chlorophylls and carotenoids content was revealed for both groups of the studied macrophytes. Leaf nitrogen content on a mass basis was identical for both groups, while the leaf carbon content was higher in emergent plants. Steady functioning of the photosynthetic apparatus of macrophytes on water-air boundary is promoted by ecological heterophily (on an example of Sium latifolium ). Use of macrophytes is perspective for the assessment of net-ecosystem carbon balance and total productivity of aquatic cenoses.