Plants need to adapt their environment to survive under natural conditions. Light is one of the most important environmental factors because light energy is necessary for photosynthesis. So far, it has remained unclear how plants acclimate to a wide range of light conditions. Recently, our group discovered function of a key regulator in light acclimation. That is, both NONPHOTOTROPIC HYPOCOTYL3 (NPH3) and ROOT PHOTOTROPISM2 (RPT2) have very important roles in light adaptation. To clarify functions of NPH3 and RPT2, it is necessary to measure light intensities correctly. Therefore, a quantum photometer (LI-250A, LI-COR) with a LI-190R-BNC-2 sensor (LI-COR) has been purchased. NPH3 and RPT2 are categorized into same family, so-called NPH3/RPT2-like (NRL) family. However, function of NRL family has not been clarified. This study will investigate roles of NRL family in phototropic responses using a quantum photometer. Useful information will be obtained by the present study in detail.