Abstract
The relationships between light intensity and the photosynthetic rate of an individual plant and a population of mat rush, the productive structure and the light-intercepting characteristics in mat rush stand were investigated to elucidate the crop photosynthetic system. The results were summarized as follows: 1. The apparent photosynthetic rate of the individual plant having the total stem surface area below about 30 dm2 was light-saturated at about 0.4 ly/min., while that of the individual plant with larger surface area of stems was not light-saturated even at 1.0 ly/min, and the highest photosynthetic rate observed in this experiment was 8.5 mgCO2/dm2/hr (Fig. 1, Table l). 2. The crop photosynthetic rate of the population with stem surface area index (SAI) of 8 was almost light-saturated at 0.8 ly/min (Fig. 2), and at this time the relative light intensity at the ground level was 50%. 3. Light extinction coefficient (K) based on SAI was nearly constant and comparatively small, while SAI was markedly increasing at the later stage of the growing period (Fig. 3, 4). 4. The ratio of the stem surface area exposed to a light intensity of 0.4 ly/min. to the total stem surface area gradually decreased as SAI became higher, and at the harvest time reached about 30% in terms of percentage (Fig. 5, 6).
