Can a plant be altruistic?

Nov 11, 2009

The concept of altruism has long been debated in philosophical circles, and more recently, evolutionary biologists have joined the debate. From the perspective of natural selection, altruism may have evolved because any action that improves the likelihood of a relative's survival and reproduction increases the chance of an individual's DNA being passed on. Social behavior, kin recognition, and altruism are well known in the animal kingdom; however, although plants have the ability to sense and respond to other plants, their ability to recognize kin and act altruistically has been the subject of few studies.

In a paper published in the November issue of the , Ph.D. candidate Guillermo Murphy and Dr. Susan Dudley explore kin recognition in Impatiens pallida, commonly known as yellow jewelweed. Yellow jewelweed individuals are often found growing in close proximity to related individuals and are known to respond strongly to aboveground competition, making this species a likely candidate for kin recognition.

Murphy and Dudley measured plants' responses to two potential cues for competition—changes in light quality (an aboveground cue) and the presence of root neighbors (an underground cue)—for plants grown with strangers and with relatives. The researchers found that the response of Impatiens plants differed depending on whether the plants grew with relatives or with strangers. This demonstrates that jewelweed is capable of recognizing kin from non-kin and shows an interesting degree of complexity since both types of responses differed from plants growing with no neighbors at all.

Among close relatives, plants did not increase resource allocation to roots or leaves. Rather, they altered their aboveground morphology by increasing stem elongation and branching. This may be an example of the plants cooperating with kin by attempting to acquire needed resources without shading nearby relatives. Yellow jewelweed is found in the understory of forests, where light may be scarce but the soil is usually nutrient-rich. Because light is the limiting factor for plant growth in this environment, a plant competing with its neighbors would be most likely to allocate resources to leaves.

For Impatiens plants grown with strangers, the plants increased their resource allocation to their leaves relative to allocation to stems and roots, an indication of a competitive response. By moving their resources into leaves, these plants not only positively affected their own growth by enhancing their ability to acquire a limited resource but also negatively affected their competitors' growth by shading nearby plants and decreasing the competitor's light acquisition abilities.

However, these differences in response based on the presence of kin or strangers were only observed in those plants grown with root neighbors, indicating that communication among roots may be necessary for plants to recognize kin. Also, changes in allocation of resources toward roots in response to light quality only occurred in plants grown with root neighbors. This is the first instance where researchers demonstrated that a plant's response to an aboveground cue is dependent upon the presence of a belowground cue. This study demonstrates that plants are social organisms. It shows that is possible among and that response to both kin and strangers depend on the ecology of the plant species.

More information: http://www.amjbot.org/cgi/content/full/96/11/1990

Source: American Journal of Botany

Explore further: Danish museum discovers unique gift from Charles Darwin

add to favorites email to friend print save as pdf

Related Stories

Plants recognize their siblings, biologists discover

Jun 13, 2007

The next time you venture into your garden armed with plants, consider who you place next to whom. It turns out that the docile garden plant isn’t as passive as widely assumed, at least not with strangers. Researchers at ...

Insects use plant like a telephone

Apr 23, 2008

Dutch ecologist Roxina Soler and her colleagues have discovered that subterranean and aboveground herbivorous insects can communicate with each other by using plants as telephones. Subterranean insects issue chemical warning ...

Super plants may fight African hunger

May 24, 2006

Ohio scientists say they've produced genetically modified cassava plants with roots more than two-and-a-half times the size of normal cassava roots.

Understanding Natural Crop Defenses

Feb 28, 2009

Ever since insects developed a taste for vegetation, plants have faced the same dilemma: use limited resources to out-compete their neighbors for light to grow, or, invest directly in defense against hungry ...

Recommended for you

Danish museum discovers unique gift from Charles Darwin

Aug 29, 2014

The Natural History Museum of Denmark recently discovered a unique gift from one of the greatest-ever scientists. In 1854, Charles Darwin – father of the theory of evolution – sent a gift to his Danish ...

Top ten reptiles and amphibians benefitting from zoos

Aug 29, 2014

A frog that does not croak, the largest living lizard, and a tortoise that can live up to 100 years are just some of the species staving off extinction thanks to the help of zoos, according to a new report.

User comments : 0