9408120 McConnaughay In plant ecological research, differences among plants of different genetic identity (e.g., species) or among plants grown in different environments are usually assessed by comparing plants at a single, often arbitrary, point in time. This static view of plant responses does not recognize the dynamic and indeterminate nature of plant development. Most characteristics of plants change during growth and development; the ratio of root: shoot biomass, for example, is usually high in seedlings ald then declines as the plant grows in size. Furthermore, plants of different genetic identity or in different environments may differ in rates of growth and development. Thus differences observed at any one point in time may not represent an adapative response to a given environment, but rather may be due, at least in part to differences in the developmental stage or size of the plant. In the last several years, there has been a widespread recognition that a broad understanding of environmental and genetic differences among plants requires a dynamic characterization of plant growth and development. We must shift our focus from snapshots of plants at one point in development to the dynamics of development itself. Biomass allocation patterns (i.e., relative amounts of biomass put in to varying plant structures) have received considerable attention from plant ecologists and plant evolutionary biologists. For example, these traits have been used to describe functional adaptations to environmental constraints. Since allocation patterns may change during plant growth and development, different allocation patterns may result from flexibility in allocation per se (allocation plasticity) or in overall plant growth (plasticity in growth or developmental rates). In cases where allocational plasticity is strictly due to alterations in growth or developmental rates, much of our current theory concerning optimal growth patterns and functional adaptations of plants to variable environments may need to be revised. We propose to separate the effects of resource availability on plant growth rate and biomass partitioning. We will grow plants in environments with different levels of resource availability (CO2, light, nutrients and water) in order to determine if differences in biomass allocation result from differences in growth rates, partitioning, or both. These experiments will provide much needed information concerning plant functional adaptations to environments differing in resource availability. ***
