Translocation (botany)
During the plant's growth period, usually during the spring, storage organs such as the roots are sugar sources, and the plant's many growing areas are sugar sinks. The movement in phloem is multi-directional, whereas, in xylem cells, it is one-directional (upwards). Other molecules like amino acids, hormones, and even messenger RNAs are also transported in the phloem through sieve tube elements.