Ecophysiological characterization of carnivorous plant roots: oxygen fluxes, respiration, and water exudation

Various ecophysiological investigations on carnivorous plants in wet soils are presented. Radial oxygen loss from roots of Droseraceae to an anoxic medium was relatively low 0.02 - 0.07 mu mol(O-2) m(-2) s(-1) in the apical zone, while values of about one order of magnitude greater were found in both Sarracenia rubra roots and Genlisea violacea traps. Aerobic respiration rates were in the range of 1.6 - 5.6 mu mol kg(-1)(f.m.) s(-1) for apical root segments of seven carnivorous plant species and 0.4 - 1.1 mu mol kg(-1)(f.m.) s(-1) for Genlisea traps. The rate of anaerobic fermentation in roots of two Drosera species was only 5 - 14 % of the aerobic respiration. Neither 0.2 mM NaN3 nor 0.5 mM KCN influenced respiration rate of roots and traps. In all species, the proportion of cyanide-resistant respiration was high and amounted to 65 - 89 % of the total value. Mean rates of water exudation from excised roots of 12 species ranged between 0.4 - 336 mm(3) kg(-1)(f.m.) s(-1) with the highest values being found in the Droseraceae. Exudation from roots was insensitive to respiration inhibitors. No significant difference was found between exudation rates from roots growing in situ in anoxic soil and those kept in an aerated aquatic medium. Carnivorous plant roots appear to be physiologically very active and well adapted to endure permanent soil anoxia.