After defoliation, Busso et al. determined axillary bud number, bud respiratory activity, and photosynthetic canopy re-establishment, for two bunchgrass species, Agropyron spicatum and Agropyron desertorum, which were exposed to droughted, natural or irrigated conditions. These field treatments were repeated annually on the same plants from 1984-1986. Tillers were sampled in the grasses after defoliation in each year and tested for bud outgrowth and metabolic activity; then early spring growth was measured each year. Two defoliations under drought conditions and one year of defoliations under mild water stress did not reduce tiller number and size. Longer periods of drought and defoliation reduced tillers, which subsequently reduced photosynthetic canopy. Continued defoliation of tillers under drought would reduce the photosynthetic area further, and probably affect the persistence of these species in the community.
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