What does the term "grafting" refer to in plant propagation?

The term "grafting" specifically refers to the technique of joining two plant parts together so they grow as one. This process often involves attaching a scion, which is a piece of a plant that will become the new growth, to a rootstock, which provides the root system and sometimes additional characteristics such as disease resistance or better growth conditions. The success of grafting relies on the compatibility of the plant tissues, allowing for the vascular systems of both parts to connect and function as a single plant. This method is commonly used to propagate fruit trees, enhance plant characteristics, and produce hybrid varieties that may not occur naturally.

The other options represent different plant propagation techniques or processes. Cloning a plant from a single leaf pertains to methods such as leaf cuttings, which is distinct from grafting. Separating roots from the main plant growth generally refers to division rather than grafting. Planting seeds directly into soil is the most basic form of seed propagation, entirely separate from the grafting technique, which involves existing plant parts rather than seeds.