[21] Phloem transport

The term phloem transport refers to the flow of assimilates from their site of synthesis or storage to their site of consumption for methodological reasons and may be separated into three phases: phloem loading, long-distance transport, and phloem unloading. To gain a better understanding of phloem transport, a close relationship between structural and functional information is necessary. Therefore, methods for studying phloem transport should include anatomical, histological, and physiological approaches. This chapter presents a selection of techniques with special emphasis on their methodological value, and open questions are briefly discussed on occasion. The different techniques are introduced by those who are working in the respective field to provide firsthand information. The development of legume seeds is characterized by a continuous transfer of assimilates from the tissues of maternal origin (seed coat) to the embryonic tissues. Photosynthetic imported from the pod wall must pass the seed coat before it is available for uptake by the embryo.