Distinguished Professor Emeritus of Plant Sciences University of California Davis
Seeds offer a unique perspective from which to view biology. An individual seed is an autonomous biological entity that must rely on its own resources (and resourcefulness) to persist after dispersal and to time its transition to germination and seedling growth to coincide with environmental opportunities for survival. At the same time, the overall behaviors of populations of individual seeds are important in agriculture and ecology. This duality of individual diversity underlying consistent population-wide behavior patterns is described quantitatively using population-based threshold (PBT) models. These flexible models can describe a diversity of responses of populations across biological levels of complexity, from the molecular to the ecological. This population variation often is termed “noise,” with analysis efforts focused on mechanisms for extracting mean “signals” from this variation to understand regulatory pathways. However, the PBT approach proposes that inherent population sensitivity distributions and recruitment phenomena underlie many fundamental biological processes. Examples from different complexity levels indicate that rather than being “noise,” built-in distributions in threshold sensitivities provide a simple and automatic system for regulating plant development and responses to metabolic and environmental signals.