Objective Plant phototropism means that trees on the side directly exposed to sunlight generally grow faster than those on the opposite,and positive phototropism is easy to observe in crown and trunk.In this study,we chose the transverse section of tree trunk to observe.The definitive intensity of plant phototropism ranges regularly from strong to weak Objective Plant phototropism means that trees on the side directly exposed to sunlight generally grow faster than those on the opposite, and positive phototropism is easy to observe in crown and trunk. In this study, we chose the transverse section of tree trunk to observe.The definitive intensity of plant phototropism peaks from strong to weak