Growth of Potamogeton pictinatus L. In the Irrigation system of the Rio Colorado, Argentina.

BENTIVEGNA D. J.; FERNANDEZ O. A.; BURGOS M. A.; SABBATINI M. R.

Foz do Iguassu

Congreso; Third International Weed Science Congress; 2000

International Weed Science Society

The most important water management problem in the lower valley of the Rio Colorado (62° 37´ W, 39° 23´S) is flow reduction in water channels caused by infestation of Potamogeton pectinatus. The aim of this study was to analyze the annual growth cycle of this submerged species in order to improve its management. Monthly plant samples were taken during the growing (Oct-Mar) of 1995/1996 (1SE) and 1997/1998 (2SE) in an irrigation channel. During these seasons water temperature varied from 12 to 25 C, and means of conductivity, turbidity, pH and water depth were 1.1 mS cm-1, 27 NTU, 7.9 and 1.2 m , respectively. Maximum plant length and maximum stem elongation rate were 150 cm and 2.1 cm day-1 during 1SE, and 267 cm and 3 cm day-1 in 2SE respectively. Regression analysys showed the same exponential growth rate of stems between October and February in both seasons, represented by the function: length = 34.1 e0.01x (x= days of growth). The average above ground plant growth rate was 9.9 mg DW day-1 for both seasons. There was a continuous increase of plant biomass with a peak in February of 802 g DW m-2 in 1SE and 1656 g DW m2 in 2SE, with an average weight gain of 6.56 g DW day-1. The DW leaves/ DW stems ratio decreased from 7.2 in October to 1.0 in January. Maximum chlorophyll content, measured only in 2SE, had a peak of 4.1 mg g DW-1. Despite the growth differences found between seasons, this study found that plant growth was most rapid early in each season (Oct-Dic), and the available habitat in the water channels was occupied by P. pectinatus by December.