What are changes that a plant makes to survive in its environment?

Plants in different environments makes changes in its structure when it starts growing. These are adaptations. For example Cactus are made up of a fleshy leaves with no leaves except for thorns which plays an important role in reducing water through evaporation (transpiration). Pine trees as we know are conical and its leaves are needle-shaped so as to reduce water loss. Under various changes, their normal disposition changes. Their structure changes for the worse.