Abstract
The factors influencing photosynthesis are chiefly light-intensity and temperature, the former being most important. Therefore, it is important to study the relation between the diurnal change of the amount of dissolved oxygen in the water produced by the photosynthetic reaction of aquatic plants and the solar radiation which is the amount of sun-light.
The Ohori, a shallow moat, situated near the Central Meteorological Observatory, Tokyo, is characterized by the high oversaturation of oxygen due to the vigorous activity of Phanerogamous aquatic plants, such as Potamogcton cripsis L. and Hydrilla verticillata var. Roxburgii Casp. which grow in the moat luxuriantly in the warmer season, and, in addition, the great abundance of phytoplankton in the water. It is a suitable microcosmos to learn the mutual relationship between biocinosis and biotop.
Observations were made from 26 to 31, March, 1932. On 30, the dissolved oxygen contained in the surface water was 7, 39c.c. per liter at 7h. and 11, 42c.c. (150% in 100O2/O'2) at 18h., which was the maximum of the day, and after then it decreased gradually. The maximum at the surface layer came about an hour later than that at the bottom.
As far as the present observations were concerned, the author could not find out the relationship numerically between the O2-production and the amount of the solar radiation correspondingly for the unit time, still it is recognizable that a lineal relation exists between the increased volume of O2 from the early morning and the amount of the solar radiation which was summed up from sun-rise till each time of the observation. The correlation coefficients are +0, 94, ω=±0, 069 and γ=+0, 96, ω=±0, 064 at the surface and the bottom layer respectively on March 30.
As regards the fact that, in spite of rapid waning of the solar radiation in 16h.-18h., the amount of O2 is still increasing, the author reserves to dare to explain and awaits more exact experiments and further studies.
