Influence of Temperature and Light on Early Growth of Potamogeton gramineus L.

ABSTRACT

Early growth of Potamoaeton gramineus L. was evaluated at several combinations of temperature (10 to 35 C) and light (7 to 213 umol m⁻² s⁻¹) in laboratory cultures. Leaf production rates were positive except at 35 C, and generally increased at higher light levels. Leaf production was reduced at 10 or 35 C. At low light levels (< 65 umol m⁻² s⁻¹), elongation rate increased with temperature. The maximum rate occurred at 25 or 30 C. At higher light levels, elongation rate decreased at higher temperatures. At low light levels (< 25 umol m⁻² s⁻¹), dry weight decreased over time. At these light levels, rates were more negative at high temperatures. At high light levels (> 65 umol m⁻² s⁻¹) dry weight increased and appeared to be a function of temperature. At ≥ 65 umol m⁻² s⁻¹ P. gramineus was photosynthetically sufficient within 4 weeks of sprouting. Comparison of P. gramineus and P. pectinatus showed that P. gramineus would not grow as rapidly under early season conditions.