SHOOT THRUST AND ITS ROLE IN PLANT COMPETITION

1. The generation of shoot thrust was measured in eight contrasted herbaceous species (Arrhenatherum elatius, Bromus erectus, Campanula rotundifolia, Cerastium fontanum, Hypericum perforatum, Koeleria macrantha, Poa trivialis and Urtica dioica) using a framework of weighted windows that could be opened by an expanding shoot. 2. The species that occur as vegetation dominants in their usual habitats (A. elatius, B. erectus and U. dioica) were found to have the greatest ability to generate thrust. 3. To test the prediction that shoot thrust was positively related to competitive ability, additional data were obtained by growing all eight species together in a productive turf in a glasshouse. 4. The rate of development of thrust was positively correlated with an index of competitive ability obtained in the productive, undisturbed conditions of the mixture experiment. 5. When associated with certain other attributes such as a tall leaf canopy, shoot thrust may be an important characteristic influencing the ability to forage for resources during competition and the potential of a plant to attain dominance in vegetation.