Salts and water in hydroponic plants are absorbed by

The correct option is: "Outer Layer of plants".

In soil-based agriculture, plants rely primarily on their root systems to extract water and essential mineral salts from the surrounding soil. However, hydroponics is a method of growing plants without soil, where the plants are instead suspended in a nutrient-rich, aqueous solution.
Because the plants are directly bathed in or continuously sprayed with this nutrient solution, absorption is not restricted solely to the roots. Instead, the outer layer of the plant—including the specialized dermal tissues and external cell walls that come into direct contact with the liquid medium—plays a primary and direct role in absorbing both water and dissolved salts.