In which two islands did the portuguese have their sugar plantations?

The Portuguese had their sugar plantations in the islands of Madeira and Sao Tome.

Explanation:

-The island of Madeira is an island located in the Atlantic Ocean, west of the African coast.  The first relevant agricultural activity was the harvest of wheat grain. Initially, colonists produced wheat for their own subsistence, but later it became an export product for the kingdom.

However, cereal production went into decline. To overcome the crisis, Prince Henry ordered the sugarcane to be planted on the island. The production of sugar attracted the island to Jewish, Genoese and Portuguese merchants.

The cultivation of sugar cane was by excellence the engine of the economy of the island. The production of sugar grew in such a way that a great need for labor arose. To cope with this shortage, slaves were brought to the island from the Canary Islands, Morocco, Mauritania and, subsequently, from other parts of Africa. The cultivation and industry of sugarcane was developed until the seventeenth century.

-Sao Tome is the largest island of Sao Tome and Principe, which was a Portuguese colony in Africa until 1975.  By the middle of the sixteenth century, and with the help of the slaves, Portuguese settlers had turned the islands into the main exporter of sugar from Africa.