The PMA symposium series was initiated in 2003 by LIAMA, the Sino-French Laboratory for Computer Sciences, Automation and Applied Mathematics. PMA multidisciplinary events are addressed to plant biologists, mathematicians and computer scientists with an interest in plant growth modeling, simulation, visualization and their applications in plant and crop sciences, forestry, agriculture, environmental sciences, ecology and virtual reality. PMA'12, the fourth conference in this series, took place in Shanghai, China, organized by CASIA and CIRAD, with the supports of several Chinese and French Institutes (CAU, PICB, CAS, NSFC, INRA, French Embassy in China, Consulate General of France in Shanghai). This Proceedings volume presents the technical and scientific results presented at PMA'12, both as oral communications and posters. Regular and short papers in the following subjects have been published: - Concepts and hypotheses in plant modeling; - Plant system modeling; - Plant-environment interaction/feedback modeling ; - Data acquisition and application of plant models in agronomy, forestry and horticulture; - Computational and mathematical methods in plant modeling; - Plant and landscape visualization; - System simulation and implementation. Readers will find new ideas and research topics in this book which is rich in diversity of approaches, scales and applications concerning plant growth models