Why Do Plants Need Roots?

Roots are one of the most vital organs in plants. These are the parts where no leaves or nodes are present and are mostly under the soil.
A plant needs roots for two chief reasons: as a mean of anchorage or support, and to absorb water and mineral salts from the soil.

Carrot the a root of its plant.

The root of most plants grow in the soil but they don't just sit there, but seem to reach out in the soil to help the plant grow. By elongating near their tips, roots are always coming in the contact of new portions of the soil.
Thousands of tiny root hairs project from the surface of the young root to absorb several mineral salts and other materials from the soil.That's why when a young root is drawn out of the soil, soil particles often cling to the root hairs.
Some plants have taproots. A taproot is a single root and much larger than any of the branch roots. Other plants have not one large but several small, equal sized roots. These form a fibrous root system.

Orchid & Sweet Potato

Grasses have fibrous root system. Soil in which there are many fibrous roots is protected from erosion. In other plants, most of the roots grow from stems. For example, the geranium.
As roots grow older, some of them store large quantities of sugar and starch. Beet and sweet potatoes are examples of this. A sweet potato is a root, but Irish potato, with its eyes, is a stem.
Not all plants have roots that grow in the soil. Some tropical orchids that grow on trees have spongy roots that grow in the air to absorb moisture. Both the English ivy and poison ivy cling to walls or trees by means of their tiny, little aerial roots. Some plants have special roots that develop from the stem above the ground and grow down into the soil, forming props. A few roots, such as the sweet potato, form buds that grow into leafy branches and can be used to propagate the plant.
Roots, either large or small, are crucial for the survival of any plant or tree.