The primary productivity and physiology of Ceratophyllum demersum. I. Gross macro primary productivity

Abstract

An artificial laboratory stream was used to study production in Ceratophyllum demersum under various conditions of light intensity, light quality, day length, and water flow. An incandescent illumination of 1500 f.c. over a 12 hr day length gave optimum production. Moderate amounts of red light gave the greatest increase in wet weight but full red light was inhibitory. Blue light, rather than white light, controlled internode length, but small amounts of red light did not cause any inhibition of this internode lengthening. Production appeared to increase with water flows (current) up to 0.54 cm/sec, but this could have been due to temperature effects. Bud formation was arrested in the slowest water flow tested, viz. 0.46 cm/sec. This suggests that vegetative propagation is retarded by slow water flows. Neither length nor the number of leaves per node showed any response to current or temperature.