CO2 assimilation by Dryas integrifolia on Devon Island, Northwest Territories

Abstract

In situ measurements of CO2 assimilation by Dryas integrifolia at different stages of development and under different environmental conditions were made on Devon Island, Northwest Territories. Dryas can fix CO2 in excess of respiration over a 24-h period under conditions of clear nights and cloudy days. The maximum net assimilation rate measured was 4.2 mg g−1 dry weight h−1. The maximum amount of CO2 fixed in 24 h was 61.54 mg g−1 dry weight. Maximum net assimilation occurred at 8 to 10 °C leaf temperatures. Positive net assimilation occurred at 1 °C leaf temperature. Light compensation was shown to be less than 0.04 langley min−1. Leaf temperatures were always greater than ambient. The maximum leaf temperature measured was 39 °C. Net assimilation rates appear to decrease as the season progresses.