The rate of movement of materials in the sieve elements can be expressed in two ways: as velocity, or as mass transfer rate. In early publications reporting on rates of transport in the phloem, what is the velocity and the mass transfer rate? i) velocity-centimeters per hour (cm h-1) and mass transfer- grams per hour per square centimeter (g h-1 cm-2) ii) velocity-the linear distance traveled per unit time and mass transfer rate-the quantity of material passing through a given cross section of phloem or sieve elements per unit time. iii) velocity- the quantity of material passing through a given cross section of phloem or sieve elements per unit time and mass transfer rate- the linear distance traveled per unit time iv) velocity- per hour per square centimeter (h-1 cm-2) and mass transfer- kg centimeters per hour (cm h-1) -triyambak.org