ABSTRACT

Gas-exchange data for actual or synthesized crop canopies, enclosed in controlled-environment chambers, have often been used for predicting canopy photosynthesis vs. intercepted light and other environmental variables. An associated model is needed for predicting intercepted light as a function of the leaf-area index as a growing season progresses. The generation and use of controlled-environment data for predictive purposes are limited by disturbances in the microenvironment caused by enclosing plants. This chapter focuses on the problem of predicting gross photosynthate supply to improve the carbon balance approach. Such balances are important parts of many models predicting photosynthate partitioning for various growth processes, as well as abscission or induced dormancy of various plant organs. One important factor controlling crop photosynthesis is the canopy leaf area index (LAI) and how much light it intercepts. For describing gross photosynthesis vs. intercepted light, initial slopes of net photosynthesis vs. total irradiance probably are adequate for crops with reasonably large LAI values.