The main function of the inner bark of a woody plant is to

The inner bark of a woody plant is scientifically known as the phloem [1][t1]. Its primary function is the translocation of food, specifically the products of photosynthesis like sucrose and sap full of sugar, from the leaves to the rest of the plant [1][c1][c4]. This transport system moves energy stores to various parts of the tree, including roots, fruits, and growing organs, to meet the plant's metabolic needs [c2][c4]. While the xylem (found in the wood or sapwood) is responsible for transporting water and minerals from the roots to the leaves [c3][c5][t1], the phloem facilitates the movement of organic nutrients in both upward and downward directions through sieve tubes [c4]. The outer bark, in contrast, serves as a protective layer against environmental factors and moisture loss [c1][t1].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 13: Plant Diversity of India > Bark; > p. 204