Plants Can Tell Who's Who

According to an article that I read in the New Zealand Herald last week, it seems that plants are able to tell relatives apart from strangers. The article suggested that plants are operating on a higher cognitive level than we give them credit for.

I've reprinted it below for your viewing pleasure. It is from the 19 June 2007 edition.

What will the vegans eat now? Researchers at McMaster University have found that plants get fiercely competitive when forced to share their pot with strangers of the same species, but they're accommodating when potted with their siblings. "The ability to recognise and favour kin is common in animals, but this is the first time it has been shown in plants," said Susan Dudley, associate professor of biology at McMaster University in Hamilton, Canada. "When plants share their pots, they get competitive and start growing more roots, which allows them to grab water and mineral nutrients before their neighbours get them. It appears, though, that they only do this when sharing a pot with unrelated plants; when they share a pot with family they don't increase their root growth. Though they lack cognition and memory, the study shows, plants are capable of complex social behaviours such as altruism towards relatives, says Dudley.

If I were looking for a non-biological explanation for this phenomenon, I would mention Rupert Sheldrake's theory of morphic resonance fields, which basically states that invisible energy patterns or morphic fields surround and affect all living things. Organisms that have surrounding energy fields of similar vibrations can communicate telepathically, and perhaps that is what these plants are doing.

However, a more logical explanation would be the biological concept of resource competition. According to the article, a plant grows bigger when it is potted with an unrelated member of its species. One obvious thing to look for is at what time each day the plant absorbs the most water and mineral nutrients. Siblings are likely to all operate to the same schedule, since their genetic makeup is similar. Therefore, they'll use available resources less efficiently than strangers that operate to different schedules.

An alternative explanation is the biological process known as allelopathy, where one plant harms another with specific biomolecules, in order to hinder this plant's growth and further its own. According to Wikipedia, "Although allelopathic science is a relatively new field of study, there exists convincing evidence that allelopathic interactions between plants play a crucial role in both natural and manipulated ecosystems. These interactions are undoubtedly an important factor in determining species distribution and abundance within some plant communities."

In any case, concluding that plants can "recognise" relatives and strangers seems a bit suspect. We have brains to perform this task. Plants do not. The researcher also makes the assumption that plants are capable of complex social behaviours such as altruism towards relatives. That's quite a leap to make. Looks to me like another case of anthropomorphism.