Leaf CER from Post‐Flowering to Senescence of Field‐grown Soybean Cultivars1

Data were collected continuously on the leaf CO2 exchange rates (CER) of field‐grown soybean cultivars. These data were recorded during two seasons from post‐flowering through leaf senescence. The soybean leaves were remarkably insensitive to most environmental conditions. Light saturation at 90 to 100 nE cm−2 sec−1 was readily achieved on most days and then, CER essentially plateaued for most of the midday hours. Only cool night temperatures significantly altered CER. When leaf senescence was uninterrupted by a cool night, CER decreased slowly and gradually over a 10 to 14‐day period. Substantial differences among cultivars were observed both in the maximum CER achieved and in the persistence of high CER throughout the season. Cultivars that showed superior CER did so consistently between the 2 years.