Photosynthesis Under Field Conditions. IX. Vertical Distribution of Photosynthesis Within a Corn Crop

The vertical distribution of the photosynthetic fixation of carbon dioxide within a crop of corn was calculated from carbon dioxide profile data and transfer coefficients obtained by analysis of windspeed measurements. Infrared analyzers were used to measure the carbon dioxide concentration at several heights within and above the crop. The calculated total fixation for the day was approximately 60 g CO? m-? (equivalent to 470 pounds of sugar per acre per day). The results demonstrated the importance of the upper leaves in the fixation of carbon dioxide and showed the increased fixation by the lower leaves during periods of high light penetration. There was some indication that a coupling existed between the level of windspeed and fixation under conditions of high light and relatively low windspeed. With refinement in technique the method could be used to obtain more quantitative estimates of the distribution of photosynthesis in other crops