It has been hypothesized that plants compete actively by allocating more resources to competitive organs and activities in response to neighbors, and this reduces population performance, such as yield in crops. Root proliferation and reduced aboveground growth in response to the presence of roots of a neighboring plant in experiments with vs. without root dividers between pairs plants has been reported in several studies, but this result has been criticized as a possible artifact resulting from differences in soil volume available to roots in the two treatments. To addressed this possible confounding effect, we conducted a pot experiment with a traditional landrace and a modern cultivar of spring wheat (Triticum aestivum). Pairs of spring wheat plants were grown in pots with two types of root dividers (a) film, which completely divides the soil into two volumes, and (b) fine nylon net, through which roots cannot grow but chemicals can move. We hypothesized that the root proliferation in response to root interactions will reduce aboveground growth.
Results/Conclusions
Wheat plants produced significantly more belowground and less aboveground biomass when interacting through the net dividers than when roots were completely separated. This effect was smaller, but still significant in the modern cultivar. Our results confirm neighbor-induced root proliferation resulting in a "tragedy of the commons" in an important crop species. The results also suggest that this response has decreased over the course of crop breeding, due to inadvertent “group selection”, and that there is still potential to increase yields by further reducing this response.