An Analysis of Light Intercepting Characteristics in Rice by Using Simple Integrated Solarimeter

Akihiro ISODA, Takao YOSHIMURA, Toshio ISHIKAWA, Yasushi NAKAMURA, Hiroshi NOJIMA and Yasuo TAKASAKI (* Image and Remote Sensing Research Center, Chiba Univ.)

Abstract : Light intercepting_ characteristics of two typically different plant types in rice were examined by using the simple integrated solarimeter. This solarimeter is a piece of the film, which can measure radiation by remaining percentages of dye after the exposure to radiation. This sensor has several benefits compared with usual measuring instruments, which are to be l) unnecessary of any electric sources, 2) cheap and mass-productive easily, 3) suitable to integrate solar radiation for a day to a few days, 4) easy to deal in out-door, 5) possible to use on a leaf surface because of its small size (12mm X 35mm) and light weight (70mg) , and 6) possible to use in many points at the same time. Shinrei (short-culmed and panicle number typed cultivar) and Tamanishiki (long-culmed and panicle weight typed cultivar) were used in this experiment. After planting, plants were transplanted to ll500Oa Wagner pots as one plant per pot, and were arranged as 33 pots per m2. Experiments were done on 11, 12 August (before heading) and 30, 31 August (after heading) in 1988. Sensor films were put on every leaf surface at the 20cm (11, 12 August) and 10cm (30, 31 August) height intervals for one plant of each cultivar. On 11, 12 August, Shinrei had larger values than Tamanishiki in the mean, the maximum and the minimum values of intercepted radiation on leaf surfaces at the uppermost layer (Shinrei 50cm, Tamanishiki 70cm) . At the second layer from the uppermost layer, there was no marked difference in these values between the two cultivars. On 30, 31 August, the mean, the maximum and the minimum values of intercepted radiation for Shinrei were larger than those for Tamanishiki. At the layers lower than the second layer, however, the amounts of intercepted radiations for Tamanishiki were less than 2MJ/m2/2days, while those for Shinrei decreased gradually toward the basal layer. Shinrei also showed larger mean values of intercepted radiation on total leaf surfaces than Tamanishiki at the both experiments. At the upper layers, the percentages of the mean values of intercepted radiation against the global solar radiation were larger than the values of the relative light intensities at the both experiments. At the lower layers, however, those values for Tamanishiki at the first experiment and for Shinrei at the second experiment were a little small in comparison with the values of the relative light intensities.