Journal Article

Oxygen Concentrations Inside the Traps of the Carnivorous Plants <i>Utricularia</i> and <i>Genlisea</i> (Lentibulariaceae)

Lubomír Adamec

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 100, issue 4, pages 849-856
Published in print October 2007 | ISSN: 0305-7364
Published online August 2007 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcm182
Oxygen Concentrations Inside the Traps of the Carnivorous Plants Utricularia and Genlisea (Lentibulariaceae)

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Species of Utricularia and Genlisea (Lentibulariaceae) are carnivorous, capturing small prey in traps which are physiologically very active, with abundant quadrifid and bifid glands. Traps of Utricularia have walls composed of two cell layers, and are filled with water. Diverse communities of commensal microorganisms often live inside the traps. Genlisea forms long, hollow subterranean traps of foliar origin, growing in anoxic wet substrate. Knowledge of the O2 concentrations inside Utricularia and Genlisea traps is vital for understanding their physiological functioning and conditions for the life of commensals. To test the hypothesis that prey are killed by anoxia inside the traps, and to measure respiration of traps, [O2] was measured in the fluid in mature traps of these species.

Methods

Oxygen concentration and electrical redox potential were measured using a small Clark-type oxygen sensor and a miniature platinum electrode, respectively, in the fluid of excised and intact traps of six aquatic Utricularia species and in Genlisea hispidula traps.

Key Results

Steady-state [O2] in the traps of both genera always approached zero (median 0·0–4·7 µm). The [O2] decreased after electrodes were inserted into Utricularia traps at a rate which ranged from 0·09 to 1·23 mm h−1 and was lower in traps of irradiated and intact shoots with higher [O2] in shoot tissues. Redox potential ranged from −24 to −105 mV in the traps, confirming the very small or zero [O2].

Conclusions

Very small or zero [O2], effectively anoxia, is demonstrated in Utricularia and Genlisea traps. This is probably below the critical [O2] for prey survival, and causes captured prey to die of suffocation. Internal trap glands and trap commensals are considered to be adapted to facultative anoxia interrupted by limited periods of higher [O2] after firings.

Keywords: Aquatic Utricularia species; Genlisea hispidula; intact traps; trap fluid; dissolved oxygen concentration; oxygen minisensor; anoxia; trap respiration; electrical redox potential

Journal Article.  6773 words. 

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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