what are the constituents of phloem

The constituents of phloem are sieve tubes, companion cells, phloem fibers, and phloem parenchyma. Sieve tubes are long, tube-like structures that transport sugars and other organic compounds throughout the plant. Companion cells are specialized parenchyma cells that carry out the cellular functions of adjacent sieve elements. Phloem fibers are flexible, long sclerenchyma cells that provide flexible tensile strength to the phloem tissues. Phloem parenchyma cells are unspecialized cells that store food and other substances. Together, these constituents work to facilitate the conduction of sugars and amino acids from source tissues to sink tissues where they are consumed or stored.