The Carnivorous Plant FAQ v. 12

Q: Are carnivorous plants autotrophic or heterotrophic?

A: This is one of those specific, semi-technical questions that I get from time to time which are clearly part of someone's science homework. If you fall into this category, do not copy my answer verbatim. I assure you, your teacher will catch you. (I bet you don't know about the international teacher communication network, do you? I have a special pass to it that lets me make sure you can't cheat on your homework and get away with it). So when you complete your homework, answer in your own words!

Life forms that can survive on simple molecules that are not preprocessed by other life forms. Conventional (noncarnivorous) plants are clearly autotrophs. They require water, CO2, light, and simple mineral nutrients to survive.

Life forms that require complex organic molecules that have been preprocessed by other life forms. Animals (and that includes you) are all heterotrophs. Most bacteria are heterotrophs. Parasitic and mycotrophic plants are heterotrophs.

What about carnivorous plants? They certainly benefit from gathering molecules from other life forms, so that would seem to make them heterotrophs. On the other hand, scientists have successfully grown carnivorous plants in laboratories where the carnivorous plants were not given any insect food. I've even grown Venus flytraps in terraria for two years without feeding them. In all these cases, the plants grow perfectly well as complete autotrophs. Yes, they grew more slowly and produced less seed than well-fed plants, but they survived and grew nonetheless. So while carnivorous plants may be considered heterotrophic to a certain degree, for the most part they are autotrophic just like other plants.

Recall, if you will, that perfectly normal autotrophic plants can be fertilized by adding pulverized animals to them? Don't believe me? Then go to a plant nursery and gaze in horror upon bags of "bone meal" or "blood meal". Eeek!

If you are really interested in this business, here's a bit more for you... Generally speaking, we can classify organisms by how they obtain both the ENERGY they need, and the nutrients such as CARBON. So you can get even more complicated by defining terms such as chemoheterotrophs, chemoautotrophs, photoheterotrophs, and photoautotrophs. Also, if you REALLY want to get a good grade on your assignment on autotrophs and heterotrophs, use words like "obligate" and "facultative" in your report. Don't know what these words mean? Look them up!

Page citations: none (pick up any botany text book).

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Revised: 2018
©Barry Rice, 2018