Studies on Photosynthesis in Upland Field Crops : I. Diurnal changes in the photosynthesis of eight summer crops growing in the field

Abstract

Diurnal changes in the photosynthesis of eight species of field crops were persued. The species used were: upland rice, sweet potato, soybean, groundnut, buckwheat, sesame, foxtail millet, and orchard grads. The photosynthetic rate of whole plants was measured in the field by a transportable apparatus at different stages of development in each crop. From measurements carried out from 1957 to 1959, the following results were obtained: 1) Diurnal changes in the photosynthesis of the eight species studied showed strong correlation with those in the horizontal light intensity, the correlation becoming higher and higher as the leaf area index of each species increased. No substantial relationship was observed between photosynthesis and the air temperature or the time of day itself. 2. The shape of light-photosynthesis curve was different among different species; those possessing erect leaves, e. g. groundnut, had higher values in their light saturation point, while those possessing horizontal leaves, e.g. sweet potato, had lower values.