This is a proposal for a joint international workshop for US and Japanese scientists to synthesize the current knowledge of the phenotypic plasticity of plants in response to light environments, and to discuss the future direction of plant ecophysiology as a key element to predict the ecosystem behaviors to global environmental changes. The central focus will be the great phenotypic plasticity exhibited by the photosynthetic apparatus at the leaf - whole-plant level, the traditional scale for plant ecophysiology, where great progress has been made. It is known from modeling studies that this plasticity can have a significant impact on canopy photosynthesis. However a more holistic understanding on the controls on this plasticity, including the mechanistic basis of species differences, and its implications for stand and ecosystem primary productivity is needed. This workshop will both review recent progress in understanding the controls on photosynthetic plasticity and their implications for responses to changing environments. It will be unique in considering both molecular studies of the underlying mechanisms and also the consequences for photosynthetic productivity and responses to environmental changes at the stand-ecosystem level. Ecophysiology in the US and Japan developed from different perspectives and bringing together scientists from both countries in this meeting is designed to facilitate synergistic collaborations. The conference is scheduled for October 23-26 in Nikko Japan, with funding from the Japan Society for the Promotion of Science to cover the costs of the meeting site and local travel, and the participation of Japanese scientists. This proposal will cover the costs for travel and per-diem for 13 U.S. scientists to enable their attendance. Papers presented at the workshop will be published in a special issue of an international journal.