Regeneration of reproductive structures of Potamogeton pectinatus, Ruppia maritima, Zannichellia palustris and Chara contraria: Effect of temperature

The effect of temperature on propagule germination was investigated in Pota mogeton pectinatus, Ruppia maritima, Zannichellia palustris and Chara contr aria, main aquatic weeds in the irrigation system of the lower Valley of th e Colorado River (Argentina) [Valle Inferior del Rio Colorado (VIRC, 39 deg rees 30' S and 63 degrees 00' W)]. Propagules were separated from harvested plants or from sediment collected in the artificial canal system. In the l aboratory, propagule germination was examined at temperatures ranging from 2 to 41 degrees C during 30 days, followed by an additional 30 days at 19 d egrees C. No germination was found at 2 degrees C, 36 degrees C and 41 degrees C in t he first 30 days. Except for P. pectinatus seeds from the bank, there was n o germination at 19 degrees C in propagules maintained at 36 degrees C or 4 1 degrees C. Those propagules which had been kept at low temperatures germi nated between days 30-60. The optimum germination (p< 0.05) range fluctuate d among propagules. In P. pectinatus germination was Door, but at 14 - 27 d egrees C, 82% of the tubers sprouted in the first 10 days. In the first 30 days, seeds of Z. palustris germinated 66.8% between 6 and 27 degrees C and those of R. maritima 52.3% between 19 and 24 degrees C. Oospores of C. con traria germinated a maximum of 36.6% in the optimum range 24 - 27 degrees C . We conclude that winter temperatures at VIRC would allow seed germination of Z. palustris. Optimum germination range for all propagules coincide wit h mean spring and summer temperatures, although oospores of C, contraria wo uld require higher temperatures.