Abstract
For studying photosynthetic rate of crop plants cultivated in the field, usually the natural sun-light is used as light source. However, the intensities of natural sunlight received by crop plants are not only subject to variations with the season of the year, the time of day, and the meteoro-logical conditions, but also different representation of its intensities may be observed by the change of measuning method (cf. Fig. 1). Therefore, it may be expected that the relationship between the light intensity and the photosynthetic rate varies due to the different representations of light intensities. Based on diurnal course of photosynthetic rate obtained by meanes of "infrared CO2-analysing recorder", author made two kinds of light curves by arranging photosynthetic rate in accordance with the received light intensities of normal and horizontal incidences. It can better be represented by arranging in accordance with the light intensity of horizontal incidence rather than the normal, with the light curve, which is of light unsaturating type (cf. Fig. 3). On the otherhand when the light curve is of light saturating type (cf. Fig. 2), it can be represented by arranging in accordance with either the latter or the former (regardless of isolated or community conditions).
