Complex sentence: It has a vital role in the breakdown of the sugars manufactured by chlorophyll, but in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant.
Split into simpler sentences: It has a vital role in the breakdown of the sugars manufactured by chlorophyll. But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant.