EFFECTS OF APEX CUTTING ON GROWTH OF ELODEA CANADENSIS ST. JOHN

The 5cm cut of apex of Elodea canadensis St.John caused a decrease ofbiomass by 28% synchronically. Both net photosynthetic rate (Pn) and photosyntheticproduction (PhP) of the shoot decreased by more than 50% when compared with thecontrol. The immediate decrease of biomass, length, Pn and chlorophyll a after cuttingwere observed to be different in percentage. During the 28 days of growth experimentafter cutting, when compared with the control, the growth of biomass and total shootslength (main shoot + lateal shoots) decreased by 45% and 53% respectively. Theelongation of the main shoot was nearly terminated, segmentation of shoots reducedslightly and water content increased significantly. Pn and PhP decreased in average by31% and 51% respectively. Growth of PhP reduced more in Percentage than that ofbiomass. It tOOk 21 days for PhP and 10 days for biomass to reach their preharvestlevels, 2 times longer for PhP than for biomass to recover. It is indicated that afterthe immediate decrease of the growth indices, growth of E. Canadensis decreasedconsequently. The increase of biomass, elongation of the main shoots and thedevelopment of the canopy were inhibited significantly by the cut of the apex,Nevertheless, no marked effects were found on segmentations of shoots. Themechanism of cutting on growth and recovery of submersed macrophytes wasdiscussed based on the current results and in comparison with literature.