The primary function of ___ is to store food. Its cells contain many amyloplasts that are filled with starch.

Root tubers

Explanation:

Firstly, amyloplasts are a type of plastids whose function is to produce and store starch granules. Amyloplasts are found to be numerous in the cells of storage tissues in certain plants. The ROOT TUBERS of some plants like potato stores carbohydrate in form of starch in the amyloplast organelles present in their cells.

According to this question, the ROOT, which contains numerous starch-storing organelles called AMYLOPLAST, primarily functions to store food for the plant.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.