A Canopy Model for Plant Growth Within a Growth Chamber: Mass and Radiation Balance for the Above Ground Portion

As humans move into outer space, need for air, clean water and food require that green plants be grown within all planetary colonies. The complexities of ecosystems require a sophisticated understanding of the interactions between the atmosphere, all nutrients, and life forms. While many experiments must be done to find the relationships between mass flows and chemical/energy transformations, it seems necessary to develop generalized models to understand the limitations of plant growth. Therefore, it is critical to have a robust modelling capability to provide insight into potential problems as well as to direct efficient experimentation. Last year we reported on a simple leaf model which focused upon the mass transfer of gases, radiation/heat balances, and the production of photosynthetically produced carbohydrate. That model indicated some of the plant processes which had to be understood in order to obtain parameters specific for each species. However, that model did not account for available carbohydrate balance between storage, growth, and export to new tissues. The objective of this paper is to develop a generalized model which includes layers of leaves interacting with each other. This model differs from general canopy models of field growth since in growth chambers these leaf layers differentially absorb radiation, from a spatial fixed light source above the canopy, and gases, arriving from below the canopy and being forced to pass through it. The overall approach to the calculations remains largely the same as the leaf model. Energy balances are first used to calculate gases exchange patterns. Carbohydrate production is then calculated from the light intensity and CO₂/O₂ concentrations. The productivity is then divided into respiration loss, storage for maintenance, structural growth, and export to other growing portions of the plant.