Ecophysiological Study of Roots in Carnivorous Plants

Reprinted from the Journal Trifid No. 3/2005:

LUBOMÍR ADAMEC 1)
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 0.020–0.070 μmol (O2) 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 μmol kg-1f.m. s-1 for apical root segments of seven carnivorous plant species and 0.4–1.1 μmol kg-1f.m. s-1 for Genlisea traps (Tab. 1).

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 mm3 kg-1f.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 on unit biomass and well adapted to endure permanent soil anoxia.

Tab. 1. Aerobic respiration rate of 3-cm apical root segments (R) of CPs and Genlisea traps (T) as dependent on respiration inhibitors after 3-h treatment. CN--R, proportion of cyanide-resistant respiration. Means ±1.SE intervals are shown; n=6. FM, fresh mass; DM, dry mass.

Respiration rate [μmol kg-1FM s-1]
Species and organ DM
[% FM] 		Controls 0.5 mM KCN 0.5 mM KCN
±5 mM SHAM 		CN--R
[%]
Sarracenia rubra – R 24.0 2.42±0.10a 2.47±0.14a 0.84±0.11b 64.7±5.9
Drosera capillaris – R 15.4 2.51±0.28a 2.51±0.21a 0.39±0.03b 84.0±1.7
Drosera capensis – R 10.5 2.15±0.11a 1.88±0.10a 0.46±0.04b 76.0±1.6
Drosera rotundif. – R 15.8 5.61±0.61a 5.97±0.31a 0.64±0.10b 89.2±1.8
Dionaea muscipula – R 17.3 4.72±0.50a 4.36±0.31a 1.11±0.12b 73.7±4.0
Genlisea violacea – T 6.4 0.38±0.03a 0.49±0.06a 0.067±0.008b 85.3±2.5
Genlisea hispidula – T 5.7 0.53±0.07a 0.48±0.10a 0.053±0.003b 86.9±2.6

Conclusions

  • Rates of root respiration and water exudation from excised CP roots were comparable with those reported in non-CPs in the literature or higher.
  • Generally, roots are very important for the ecophysiology of CPs.
1)
RNDr. Luboš Adamec – A scientist at The Institution of The Plant physiology in Třeboň, Dukelská 135, CZ-379 82 Třeboň, the Czech Republic.