Why carnivorous plants like wetlands

Posted on September 21, 2011

Carnivorous plants have evolved independently in several plant groups and include forms such as the sundews, butterworts, pitcher plants and bladderworts. Because such species tend to occur in low-nutrient habitats, plant carnivory has usually been explained as a way of making up for deficits in the supply of available nutrients. However, carnivorous plants are also closely associated with wet substrates, and the authors of a new study suggest that carnivory is more indicative of wetland conditions than of low soil fertility. Surveys were conducted in a Mississippi wet pine savanna that included moderately wet woodland, bogs and permanently waterlogged depressions. Distributional analyses and experiments showed that carnivorous plants were no more indicative of low-nutrient soils than non-carnivorous species. The carnivorous species occurred mainly in wetland habitats and were intolerant of dry soils. All carnivorous species produced non-porous roots with a lower maximum length (6.9 cm on average) than the roots of non-carnivorous plants (11.9 cm). Carnivorous plants were largely absent from nutrient-rich wetlands, perhaps because the rapid decomposition of organic matter led to the accumulation of sulphides and other toxins. These results are consistent with the idea that in waterlogged soils, oxygen diffusion may be too limited to detoxify the soil or to support the respiratory needs of a deep root system. As a result, plant roots are shallow and confined to the aerated soil layer near the surface. Shallow root systems explain why carnivorous plants are very intolerant of dry conditions. And because shallow roots have a limited ability to absorb nutrients, carnivorous plants have to supplement their intake with animal-derived nutrients.

Reference: Brewer, J.S., Baker, D.J., Nero, A.S., Patterson, A.L., Roberts, R.S. & Turner, L.M. 2011. Carnivory in plants as a beneficial trait in wetlands. Aquatic Botany 94, 62–70.

Posted in: nutrients, plants, wetland