Final answer:
The top part of a graft is called the scion, which is the part of the plant desired for its growth characteristics, and gets grafted onto the stock, the rooted part known for its strong root system.
Step-by-step explanation:
The top part of a graft is called the scion. Grafting is a horticultural technique where a scion, the part of the plant that is desired for its stems, leaves, flowers, or fruit, is connected to the stock, which is typically chosen for its strong root system and resistance to disease. The scion becomes the new growth of the grafted plant, producing shoots and eventually flowers and fruits, while the stock provides support and nutrients. The vascular systems of the stock and scion must closely match and fuse together to ensure a successful graft. This technique is widely used in agriculture, particularly in viticulture and the citrus industry.