Plant membrane-transport systems are important for distributing photoassimilates and nutrient elements over both short-(intracellular and cell-to-cell) and long-distance (from source organs to other parts of the whole-plant body).Although the importance of membrane-transport systems for resource distribution had been recognized several decades ago,only over the last decade has the understanding of membrane-transport mechanisms markedly improved along with the identification of diverse membrane transporters.To reflect the current progress and future trend in this exciting and expanding field of plant biology,Molecular Plant published a special issue focusing on membrane-transport mechanisms and regulation (Volume 4,Number 3,2011),which has been freely accessible online since May 2012.