Ryan Kitko (droserary) wrote in wtf_nature,
Ryan Kitko


The recent post on the genus Lithops and the comment about their morphology reminded me of something I had been thinking of posting. I figure now's a good time. The photo to the right is a member of the Lentibulariaceae, a family of carnivorous plants related to other members of the Lamiales like mints and snapdragons. This particular photo, an image of the bladder traps of Utricularia inflata is one of Barry Rice's many beautiful photos of carnivorous plants.

I realize these have been posted about before but not really in depth. The reason the Lentibulariaceae are interesting is their extremely varied morphology (from aquatic invasive species like U. inflata to alpine and tropical land plants of the other two genera, Pinguicula and Genlisea) and also their curious rapid molecular evolution and genome downsizing.

Let me explain. First, morphology. We normally think of plants as having roots that go down and shoots that go up, gravitropism at work, right? Of course there are notable exceptions, like the aerial roots of mangroves or the "knees" of bald cypress in swamps. Some members of the Lentibulariaceae, especially those in the genus Utricularia turn everything on its head. To be accurate, these plants don't have any true roots or cotyledons (embryonic leaves), nor do their "leaves" appear to be leaf-like. For many of the species, especially the aquatic ones like U. inflata, the main vegetative body part is essentially a stolon. The terrestrial species, like this one (U. longifolia) to the right, has no roots but modified stems, often called rhizoids, anchoring it in the soil. Those "leaves" you see on U. longifolia might possibly be leaves, but there's been much debate about what the proper term for them is, since they're not really true leaves. Peter Taylor, the main man who monographed this genus in 1986, revised in 1989, a monumental task, called them "modified leaf-like organs" but settled for calling them "leaves" for the remainder of the 700-page monograph to save ink. Similarly, the carnivorous traps of the genus Genlisea (photo below) that attract and capture soil protozoans are really modified underground leaves! The traps of Utricularia are of course the vacuum/suction bladders you've seen above (they actually create negative pressure inside the bladder trap!) and the traps of Pinguicula are similar to those of the sundews (Drosera), simply sticky leaves. So why the huge morphological differences? How the hell did they get like this?

Simple answer is no one's quite sure. All we know for sure is that there's been extremely rapid molecular evolution that's allowed this family to develop three very different kinds of carnivory in a relatively short period of time. Even more surprising is that some species in this genus, specifically Genlisea margaretae, have a high number of chromosomes (diploid number around 40), while the chromosomes themselves are very small. Here's the fun part: Individual chromatids of G. margaretae are even smaller than some bacterial chromosomes. As of 2006, G. margaretae has the smallest flowering plant genome ever recorded. Much smaller than the model organism, Arabidopsis thaliana. Add to the equation that among 400 other genera tested, these plants are evolving much faster than anything else in certain genes that were tested (usually ones that code for ribosomes). Fascinating, no?

Some more photos for photo junkies:

Genlisea lobata × violacea flower

Pinguicula grandiflora

Utricularia menziesii

And the one everyone says looks like a bunny rabbit:

Utricularia sandersonii

I suppose that's all for now. This whole plant family is fun to play with and relatively easy to grow, depending on the species. I have a few that are considered weeds in carnivorous plant cultivation. Can't get rid of them! And of course, there's more interesting stuff about these plants, but this is all I could think of immediately. Sources are below.

  • All the Wikipedia pages I linked to, many of which I wrote.
  • Laakkonen, L., Jobson, R.W., and Albert, V.A. (2006). A new model for the evolution of carnivory in the bladderwort plant (Utricularia): Adaptive changes in cytochrome c oxidase (COX) provide respiratory power. Plant Biology, 8: 758-764.
  • Greilhuber, J., Borsch, T., Müller, K., Worberg, A., Porembski, S., and Barthlott, W. (2006). Smallest angiosperm genomes found in Lentibulariaceae, with chromosomes of bacterial size. Plant Biology, 8: 770-777.
  • Taylor, Peter. (1989). The genus Utricularia: A taxonomic monograph. Kew Bulletin Additional Series XIV: London.
  • Tags: carnivorous plants, evolution
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