This transfer of sugars (photosynthetic) from mesophyll cells to sieve tube elements in the leaf is called as phloem loading. On the other hand, the transfer of sugars (photosynthetic) from sieve tube elements to the receiver cells of consumption end (i.e., sink organs) is called as phloem unloading.

What is unloading of phloem?

Phloem unloading is the movement of phloem sap constituents, principally nutrients (sugars, amino-N compounds, ions), signalling molecules (RNAs, proteins, phytohormones) and water, from sieve element-companion cell (SE-CC) lumens (SE-CC unloading) with subsequent cell-to-cell delivery to non-SE-CC vascular or ground ...

What is meant by phloem loading?

Phloem loading is the process of loading carbon into the phloem for transport to different 'sinks' in a plant. Sinks include metabolism, growth, storage, and other processes or organs that need carbon solutes to persist.