VARIABILITY OF PHOTOSYNTHETIC GAS-EXCHANGE PARAMETERS, DARK RESPIRATION, AND STOMATAL NUMBERS IN SPECIES OF POLYGONUM

Within the genus Polygonum a large variation was found between species with regard to stomatal number, gas phase resistance, intracellular r esistance and dark respiration. Interspecific variation in CO2 compens ation concentration and intercellular CO2 concentration at constant ex ternal concentration were comparatively small. Correlations were found between stomatal number and gas phase resistance, stomatal number and Gamma, and Gamma and the product of dark respiration rate and intrace llular resistance. The influence of dark respiration and stomatal numb er on photosynthetic gas exchange is discussed. It was concluded that dark respiration in light was enhanced by 22% as a mean value in 9 Pol ygonum species and by 62% in Polygonum lapathifolium.