Why do biennial plants often have root crops?

Biennial plants form flowers and seeds, that is, they multiply, in the second year of life. But, with the onset of unfavorable conditions, the aboveground part of the plant dies off. In order to form an aerial shoot in the second year of life, nutrients are needed. Here plants and accumulates them in the first year of life underground, forming various modifications of shoots and roots, including root crops. Examples of such plants are carrots, parsley, radishes, radishes, turnips.