Studies on Photosynthesis in Sugar Beet Plant : I. On the method of measuring photosynthesis with detached leaves.

Abstract

The method of measuring the photosynthesis with detached leaves of sugar beet plant was investigated, and some fundamental problems on measurement of photosynthesis were also examined. The results are summarized as follows. (1) The photosynthesis of leaf blade was not affected by cutting the petiole under the condition of air temperature ranging from 18°C to 28°C and of normal air humidity. (2) In order to maintain the photosynthetic ability of detached leaf as high as before excision, it was necessary to supply water to leaf blade from the cut end of petiole. And it was effective in maintenance of photosynthetic ability for a longer period, to keep the inside of the leaf chamber in high humidity and moderate temperature. (3) The leaf temperature under light intensity of about 40 Klx could be kept at the same level as the air temperature in the leaf chamber, by the placement of a water filter of adequate thickness between the light sourse and chamber. (4) There was a linear relationship between relative photosynthetic intensity and mean CO₂ concentration in the leaf chamber. This relationship was represented by the following formula; P=0.482·C-44.5, where P=relative photosynthetic intensity (P=100 at C=300ppm), and C=CO₂ concentration in the chamber. (5) The diurnal variation in photosynthetic ability was hardly detected.