Plant-herbivore interactions: Examination of potential effects of bison saliva on regrowth of Bouteloua gracilis (H.B.K.) lag

Summary Laboratory experiments were performed to determine whether regrowth of blue grama was affected by potential growth-promoting substances in saliva of North American bison. We observed no statistically significant effects of foliar application of whole bison saliva on net photosynthesis (P_N), root respiration (R_R), allocation patterns of photosynthetically fixed ¹⁴C, or regrowth rates over a 10-day period following clipping to various heights. In a 10-week experiment, there were no significant effects of saliva on leaf, crown or root growth or tiller production in plants clipped to heights of 6, 4 or 2 cm above crowns. Similarly, nitrogen-stressed plants failed to show significant changes in growth rates or tillering in response to saliva over a 3-week period. Clipped blue grama plants did exhibit significant compensatory growth responses, including higher P_N rates from 3–10 days following clipping and allocation of a higher proportion of current photosynthate to synthesis of new leaf tissue with increasing severity of defoliation. Nevertheless, unclipped plants invariably outproduced clipped plants following defoliation.