作物の瓦斯代謝作用に関する研究 : I. 作物の瓦斯代謝作用の継続的測定装置について II. 水稲の発育に伴う同化・呼吸量の消長

抄録

The apparatus deviced by us, gives a nearly instantaneous measuring of the CO₂-exchange for a whole plant under natural conditions, and the measurement can be carried for a long time. This apparatus is divided into 4 main parts: (1) The main stream system consisting of plant chamber, gas-meter and exhauster. The chamber is set upon a Wagner's pot in which the plant is cultured, the air is supplied to the chamber by driving the exhauster, and its volume indicated by gas-meter. (2) Air-sampling-cylinder. A pair of air-sampling-cylinders driving at the intervals of 5 min. alternatively, Samples 350 cc. of air per min. from main stream and delivers it to the absorber. (3) Absorber, which holds 50cc. of CO₂-absorbing solution (1/(50) NaOH+1% Butyl-Alcohol), catches CO₂ completely from the air sample. (4) An electrode, which is inserted in absorber, measuring the changes of electro-conductivity caused by CO₂ absorption with the help of Kohlraushe's Bridge. In 1953, CO₂ exchange in rice plant cultured in a pot was investigated by applying the apparatus mentioned above, and data obtained are as follows: (1) Diurnal changes of apparent photosynthesis and respiration were investigated at various growing stages. The total daily CO₂ assimilation level increases gradually in proportion to the growth, and reaches the maximum amount at the end of the vegetative stage or the beginning of the reproductive stage, then decreases gradually and keeps nearly the same level from booting to heading, and then decreases rapidly during the ripening stage. Otherwise total night respiration level increases gradually accompanying with the growth, and the maximum level appears in the stage from booting to heading, and then decreases gradually. (2) The balance between growth (dry-matter productivity) and carbon dioxide exchange. Fig. 14 shows the total daily apparent assimilation and respiration at each of the main stages of growth. The theoretical curve of increase in dry matter and the actual one are also shown here, the former is calculted from net assimilation value, assumed on the basis of chemical analysis that the dry plant material centains 44 % of carbon, and the latter is derived from the actual growth curve (fig. 15). There is approximate concordance between the experimental curve and the theoretical one in the early stages of growth, however, the former is considerably lower than the latter in later growing stages. This is due to unfavourable climate in the later stage of growth, and also due to the fact thet the estimation is made theoretically for sunny days only. (3) The relation of photosynthesis to light intensity (Lux) is illustrated in fig. 16. There seems to be different demands for light for their maximum photosynthesis according to the vegetative or reproductive stage. It will be found there is no appreciable increase in the rate of assimilation over 60∼70 K. Lux at booting stage and 50∼60 K. Lux at vegetative stage. And in both cases, when the light intensity drops under 20 K. Lux, sudden reduction takes place in the rate of assimilation. (4) During the daytime, in which vigorous CO₂ assimilation continues, CO₂ concentration in field keeps the valu of about 55 mg per 100 liters of air, in late afternoon this gradually increases and a sudden increase in CO₂ concentration takes place after sun set, and then increases gradually during the nighttime, and finally reaches the maximum value of about 70 mg per 100 liters of air berore sun rise. The concentration level decreases abruptly after the sun rise, and returns to the low daytime level of 55 mg until 10 a.m. (Received April. 4, 1954)