Measurement of Distribution of Photosynthesis in Plant Canopies

Abstract

ATTEMPTS have been made to measure or calculate photosyn-thetic activity in various morphological parts or height layers of plant canopies. This has been done by measuring dry weight changes in relation to removal of the parts¹, carbon dioxide exchange when the parts were enclosed in assimilation chambers² and a combination of progressive defoliation and whole canopy carbon dioxide uptake measurement^3,4. To study the activity in layers of the canopy, Leach and Watson⁵ placed phytometers at various points in the canopy to stimulate the photosynthesis of adjacent plant parts, and aerodynamic methods have since been used to estimate the distribution of photosynthesis in canopies⁶. By using photosynthesis response data for leaves and information about the environment in the profile, Monsi and Saeki⁷ and others^8,9 have estimated localized photosynthesis.