ROOT-GROWTH RESPONSES OF 3 GREAT-BASIN PERENNIALS TO INTRASPECIFIC AND INTERSPECIFIC CONTACT WITH OTHER ROOTS

Competition between plants for soil resources such as water and nutrients can be affected by the spatial arrangement of neighbouring root systems. Avoidance of root overlap by one or more species would lessen competition. Here, we test whether the roots of three Great Basin perennials are capable of detecting the presence of other roots, and whether root growth rate is thereby negatively affected. Root growth rates were measured for Pseudoroegneria spicata, Agropyron desertorum and Artemisia tridentata ''test'' plants, as they encountered and made contact with roots of other plants of each of the three species (''target'' plants). The root growth responses were compared with roots that did not make contact with other roots and those that contacted simulated roots made of braided dacron line. Of the twelve test-target combinations, only Pseudoroegneria roots exhibited a highly significant reduction in growth rate upon contact with roots of Agropyron. Root growth rate of two Pseudoroegneria plants of a different genotype was not affected by contact with Agropyron roots. The ability to alter root growth behaviour according to the presence or absence of specific neighbours could be beneficial if it makes resources available that would not otherwise be. It remains to be seen whether or not ''root recognition'' is an important phenomenon dictating root behaviour in the field, given resource patchiness and mycorrhizal associations.