Gymnosperm phloem does not have sieve tubes, only single cells. Sieve plates are on the side of the cell-works like a network rather than a pipe. These are called sieve areas. It is not understood how this works because sieve areas are filled with endoplasmic reticulum which blocks flow. The presence of membranes would mean that there can’t be a bulk flow, but it doesn’t seem to be possible in gymnosperms.
Recent comments