Aquatic Plant Control Research Program. Effects of Water Chemistry on Aquatic Plants. Growth and Photosynthesis of Myriophyllum spicatum L

摘要

Growth of the submersed macrophyte, Myriophyllum spictam L., was examined in nine solutions differing in major cation (Ca, Mg, Na, and K) and inorganic carbon C sub t levels. Growth experiments were conducted under two conditions differing in the relative magnitudes of gas exchange and solution volume. Under conditions of limited solution volume, growth was adversely affected by the combination of low cation (particularly Ca) and low C sub t levels. However, where solution volume was greater, there was no effect of cations. Irrespective of volume, growth was increased by increasing C sub t from 3.5 to 10.5 mg/l, but was unaffected by further increase in C sub t to 21.00 mg/l. Photosynthetic uptake of C sub t during growth reduced levels of C sub t and acidity and increased pH. Alkalinity and Ca levels were also reduced in some solutions due to the precipitation of CaCO3. Diurnal analyses indicated C sub t was not appreciably replenished during the night; thus, the experimental systems continually lost C sub t throughout the study. Initial photosynthesis rates, measured in the same solutions, indicated a strong relationship between photosynthesic and solution C sub t. Measurements of the exchange of CO2 between the atmosphere and the solution during the photosynthesis experiments revealed the potential importance of the atmosphere as a significant source of carbon. Keywords: Aquatic plants; Eurasion watermilfoil; Water chemistry.