Stock and scion are used in

• cutting

• grafting

• layering

• micropropagation

B.

grafting

Stock and scion are used in grafting. Grafting is a horticulture technique whereby tissues from one plant are inserted into those of another, so that the two sets of vascular tissues may join together. It is used in asexual propogation of commercially grown plants. 

In this technique, one plant is selected for its roots and this is called the stock or root stock. The other plant is selected for its stems, leaves, flowers or fruits and is called the scion or cion. The scion contains the desired genes to be duplicated in future production by the stock/scion plant.