In plants.

when siblings are grown next to each other in the soil, they "play nice" and don't send out more roots to compete with one another.

However, the moment one of the plants is thrown in with strangers, it begins competing with them by rapidly growing more roots to take up the water and mineral nutrients in the soil. . .

In a series of experiments, young seedlings were exposed to liquid media containing the root secretions or "exudates" from siblings, from strangers (non-siblings), or only their own exudates.

The length of the longest lateral root and of the hypocotyl, the first leaf-like structure that forms on the plant, were measured.

Additionally, in one experiment, the root exudates were inhibited by sodium orthovanadate, which specifically blocks root secretions without imparting adverse growth effects on roots.

The exposure of plants to the root exudates of strangers induced greater lateral root formation than exposure of plants to sibling exudates. Stranger recognition was abolished upon treatment with the secretion inhibitor. . .

Strangers planted next to each other are often shorter, Bais notes, because so much of their energy is directed at root growth.

Because siblings aren't competing against each other, their roots are often much shallower.

Bais says he and his colleagues also have noticed that as sibling plants grow next to each other, their leaves often will touch and intertwine compared to strangers that grow rigidly upright and avoid touching.

The study leaves a lot of unanswered questions that Bais hopes to explore further. How might sibling plants grown in large "monocultures," such as corn or other major crop plants, be affected? Are they more susceptible to pathogens? And how do they survive without competing?

"It's possible that when kin are grown together, they may balance their nutrient uptake and not be greedy," Bais speculates.

The research also may have implications for the home gardener.

"Often we'll put plants in the ground next to each other and when they don't do well, we blame the local garden center where we bought them or we attribute their failure to a pathogen," Bais says. "But maybe there's more to it than that."

It seems to me that planting unlike cultivars in soil with sufficient moisture and nutrients would result in plants that have good root systems and good leaf systems since the roots would enable them to eat more. I wonder how flowers and seed would be affected? How far does the competition go?

This may be an explanation of and argument for polyculture, but it would have to be done with some knowledge of how to balance the competitors, though I suppose that live-and-learn trail and error would eventually sort the competitors.

I'd also like to see some tests done in which the various cultivars occupied different parts of the biotope space: feeding at different soil depths and with slightly different growth and maturity phases.