Communication between sagebrush and wild tobacco in the field

Communication between plants has not been widely accepted by most ecologists. However. recent field experiments indicated that wild tobacco plants became more resistant to herbivores when grown in close proximity to clipped sagebrush neighbors. Tobacco plants grown within 15 cm of sagebrush that had been either manually clipped with scissors or damaged by herbivores experienced less naturally occurring folivory than tobacco plants with unclipped neighbors. These results were consistent over five field seasons and involved treatments that were randomly assigned and well replicated. Associated with lower levels of herbivory were increased activities of polyphenol oxidase in tobacco foliage near clipped sagebrush neighbors. Experiments that blocked either air or soil contact between sagebrush and tobacco indicated that the communication was airborne rather than soilborne. Alternative explanations involving altered microenvironmental conditions or avoidance of clipped sagebrush by herbivores were not supported. Much remains to be learned about the natural history of this phenomenon. Apparently the plants must be in close proximity for communication to occur. Preliminary results suggest that communication between sagebrush and other plants may also occur. The mechanisms of communication as well as its ecological and evolutionary significance remain unknown. (C) 2001 Elsevier Science Ltd. All rights reserved.