What do the term host and …

A plant (or animal) which lives on or inside another organism (called host) and derives the food from it, is called a parasite.

Those non-green plants which obtain their food from the living bodies of other plants (or animals) are called plant parasites.

The living organism (from whose body food is obtained) is called ‘host’ of the parasite. 

The parasite plants climb on the host plants from which they get all the food.

A parasite plant produces certain special type of roots (called sucking roots) which penetrate into the host plant. The parasite sucks the food materials from the host through these special roots.

For example : Cuscutta. It is called Amarbel in Hindi. Cuscutta plant is a yellow, tubular structure twining around the stem and branches of a tree. The tree on which Cuscutta plant climbs is called its host. Since Cuscuta plant does not have the green pigment called chlorophyll, it cannot synthesise its own food. Cuscuta plant takes readymade food from the tree (or plant) on which it climbs. Since Cuscuta plant deprives the host tree of valuable nutrients, it is called a parasite.

Examples of plant parasites are Mistletoe, Wheat rust and Corn smut.