抄録
The young sporophyte of Ecklonia kurome Okamura is growing on the population floor. This study was designed to estimate the daily light compensation point of the young E. kurome with a mathematical model based on photosynthesis-irradiance relationships, diurnal changes in solar radiation and relative irradiance at the sea floor in the habitat around the Umashima Island, Yamaguchi Prefecture. The samples were collected at a depth of 5m at the habitat. Photosynthesis-irradiance relationships of the young E. kurome using a productmeter were fitted by a hyperbolic tangent function. Maximum gross photosynthesis, respiration, light saturation and light compensation point were 30.0 LO2 cm-2 h-1, 1.88 LO2 cm-2 hr-1, 67.0 mol m-2 s-1 and 4.20 mol m-2 s-1, respectively. The daily light compensation point of the young E. kurome estimated by the mathematical model was 0.73% of the irradiance on the sea surface for a day of average solar radiation during study period. This estimated value agreed with the light condition actually measured at the growing site of young E. kurome on the population floor, which was 0.74% of the irradiance on the sea surface. The present study was able to clarify the daily light compensation point of young E. kurome from the results of the mathematical model considered with the both of photosynthetic property and the measurement in the field.
