Epidermal cells of plant roots increase their absorption surface by having

The epidermal cells of plant roots increase their absorption surface area through the development of root hairs. These structures are unicellular extensions of the root epidermal cells that significantly expand the total surface area available for the uptake of water and essential minerals from the soil [1]. By increasing the absorptive surface and improving physical contact with soil particles, root hairs facilitate more efficient nutrient and water transport into the plant's vascular system [1]. While stomata are present on leaves and stems for gas exchange and transpiration control, they are generally absent or non-functional for absorption in roots [3]. The endodermis serves as a selective barrier within the root rather than an external surface-increasing structure, and scales are typically protective rather than absorptive. Thus, root hairs are the primary specialized epidermal modifications for maximizing absorption [1].

Sources

1. [1] https://www.nature.com/scitable/knowledge/library/water-uptake-and-transport-in-vascular-plants-103016037/
2. [3] https://en.wikipedia.org/wiki/Root_hair