Leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning according to circadian rhythm controlled by biological clock. Our studies on the circadian leaf-movement, called nyctinasty, led to discovery the leaf-opening and leaf-closing substances that control nyctinasty. We revealed that some receptor for the leaf-opening subustance of Cassia mimosoides L., potassiumu lespedezate (1, bioactivity: 1×10^<-6> M), is localized in motor cells by using fluorescent probe (2), and then we synthesized 2 type photoaffinity probes based on 1 to identify the receptors. One is the probe 3 (bioactivity: 5×10^5 M) induced photoaffinity group and biotin unit into 6'-position of the glycon moiety, which remained high bioactivity because of bulky photoaffinity unit away from active aglycon moiety. The others are 4 (bioactivity: 8×10^<-5> M) and 5 (bioactivity: 1×10^<-4> M) induced photoaffinity unit into 2'-position of the glycon moiety, which are expected high labeling yield because of adjacent photoaffinity group to aglycon moiety. Then we collected large amount of motor cells by cutting sections of plant pulvini containing motor cells under the stereoscopic microscope. Successive homogenization and centrifugations gave the membrane fraction. After being added 4 and irradiated UV-lamp (365 nm), the membrane fraction was analyzed by SDS-PAGE, transferred to PVDF membrane and detected by chemiluminescence. In the result of it, we detected specific bands at 210, 180 kDa which disappeared under the condition of presence of 10000-fold molar excess non-labeled leaf-opening substance. Next, we examined the localization of these specific bands of proteins. The photolabeling experiment was carried out for the membrane fraction prepared from cutting sections of plant leave, but these bands were not found.