and as an area Extension agent with Colorado State University. Mr. Murphy is currently completing a Ph.D. program in plant physiology. His dissertation research focuses on the environmental, developmental, and physiological mechanisms that regulate tiller initiation in grasses. Mr. Murphy's research interests include physiological plant ecology, plant population ecology, photobiology and plantherbivore interactions. David D. Briske received his B.A. in botany fromNorth Dakota State University in 1973 and his Ph.D. in range science from Colorado State University in 1978. His research and teaching interests include physiological plant ecology, developmental plant morphology, plant-herbivore interactions, clonal plant biology, plant population ecology, and grassland ecology. The goals of Dr. Brisk& research program are to develop a greater understanding of the ecophysiology and population ecology of the bunchgrass growth form which dominates rangelands throughout the world and to generate and synthesize ecological information necessary to evaluate current strategies and provide new alternatives for grassland conservation and management.

Depressions in the red to far-red ratio (R:FR) of solar radiation arising from the selective absorption of R (600-700 nm) and scattering of FR (700-800 nm) by chlorophyll within plant canopies may function as an environmental signal directly regulating axillary bud growth and subsequent ramet recruitment in clonal plants. We tested this hypothesis in the field within a single cohort of parental ramets in established clones of the perennial bunchgrass, Schizachyrium scoparium. The R:FR was modified near leaf sheaths and axillary buds at the bases of individual ramets throughout the photoperiod without increasing photosynthetic photon flux density (PPFD) by either (1) supplementing R beneath canopies to raise the naturally low R:FR or (2) supplementing FR beneath partially defoliated canopies to suppress the natural R:FR increase following defoliation. Treatment responses were assessed by simultaneously monitoring ramet recruitment, PPFD and the R:FR beneath individual clone canopies at biweekly intervals over a 12-week period. Neither supplemental R nor FR influenced the rate or magnitude of ramet recruitment despite the occurrence of ramet recruitment in all experimental clones. In contrast, defoliation with or without supplemental FR beneath clone canopies reduced ramet recruitment 88% by the end of the experiment. The hypothesis stating that the R:FR signal directly regulates ramet recruitment is further weakened by evidence demonstrating that (1) the low R:FR-induced suppression of ramet recruitment is only one component of several architectural modifications exhibited by ramets in response to the R:FR signal (2) immature leaf blades, rather than leaf sheaths or buds, function as sites of R:FR perception on individual ramets, and (3) increases in the R:FR at clone bases following partial canopy removal are relatively transient and do not override the associated constraints on ramet recruitment resulting from defoliation. A depressed R:FR is probably of greater ecological significance as a signal of competition for light in vegetation canopies than as a density-dependent signal which directly regulates bud growth and ramet recruitment.

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