Plantas insectívoras

Plant and Soil (2005) 274:127–140 DOI 10.007/s11104-004-2754-2

Ó Springer 2005

The roots of carnivorous plants
Wolfram Adlassnig1, Marianne Peroutka1, Hans Lambers2 & Irene K. Lichtscheidl1,3
Institute of Ecology and Conservation Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria. 2School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University ofWestern Australia, Crawley WA 6009, Australia. 3Corresponding author*
Received 30 April 2004. Accepted in revised form 31 August 2004
1

Key words: carnivorous plants, insectivorous plants, morphology, nutrition, root

Abstract Carnivorous plants may benefit from animal-derived nutrients to supplement minerals from the soil. Therefore, the role and importance of their roots is a matter ofdebate. Aquatic carnivorous species lack roots completely, and many hygrophytic and epiphytic carnivorous species only have a weakly developed root system. In xerophytes, however, large, extended and/or deep-reaching roots and sub-soil shoots develop. Roots develop also in carnivorous plants in other habitats that are hostile, due to flooding, salinity or heavy metal occurance. Information about thestructure and functioning of roots of carnivorous plants is limited, but this knowledge is essential for a sound understanding of the plants’ physiology and ecology. Here we compile and summarise available information on: (1) The morphology of the roots. (2) The root functions that are taken over by stems and leaves in species without roots or with poorly developed root systems; anchoring andstorage occur by specialized chlorophyll-less stems; water and nutrients are taken up by the trap leaves. (3) The contribution of the roots to the nutrient supply of the plants; this varies considerably amongst the few investigated species. We compare nutrient uptake by the roots with the acquisition of nutrients via the traps. (4) The ability of the roots of some carnivorous species to toleratestressful conditions in their habitats; e.g., lack of oxygen, saline conditions, heavy metals in the soil, heat during bushfires, drought, and flooding.

Introduction to carnivorous plants Plants benefit in many ways from animals; e.g., animals play a role as pollinators and as dispersers of fruits. However, animals may also contribute to a plant’s nutrition by being caught and digested. This phenomenonof carnivory has fascinated the scientific community ever since Darwin drew attention to it (Darwin, 1875). Although carnivorous plants can obtain water and at least some minerals from the soil, they also extract nutrients from captured animals.
* E-mail: irene@pflaphy.pph.univie.ac.at

Carnivorous plants attract their victims by means of scent, colouration and nectar (Lloyd, 1942). They are ableto trap and retain their victims, kill them, and digest their soft tissues, and take up at least part of their contents (Juniper et al., 1989; Lloyd, 1942). This whole process is achieved by highly specialized leaves, which have been transformed into various types of traps. Therefore, the leaves may take over functions that are usually restricted to the roots of noncarnivorous plants. The generalfeatures of carnivorous plants have been reviewed in detail by Juniper et al. (1989). Five types of traps can be distinguished:

128  Adhesive traps produce sticky mucilage that is able to glue little animals to the leaves. Such ‘fly-paper’ traps may actively roll over their victims (Drosera, Pinguicula) or they remain motionless (Byblis, Drosophyllum).  In steel traps, the leaf forms twolobes, which snap around animals that touch sensitive trigger hairs on the surface of the lobes (Dionaea, Aldrovanda).  In pitcher traps, leaves have been transformed to a pit that contains a pool of digestive enzymes (Darlingtonia, Nepenthes, Sarracenia, Cephalotus, Heliamphora). Animals are attracted towards the rim, and glide into the pit along the slippery inner surface, which prohibits...