Which nutrient movement process is driven by a concentration gradient and does not require energy?

• A. Mass movement with water flow
• B. Active transport requiring energy
• C. Capillary action
• D. Diffusion

Answer: (D)

Diffusion is the movement of nutrients down their concentration gradient, and it doesn’t require energy because it happens by the natural, random motion of molecules. When there’s more of a solute in one area than another, molecules spread out until the concentrations become more even. This passive process is fundamental for how nutrients spread through soil solution and reach micro-sites where plants and microbes can use them. The rate depends on how steep the concentration difference is, the temperature (which speeds up molecular motion), and the size or charge of the particles and how easily they move through the medium. In contrast, processes that involve a need for energy—such as moving substances against their gradient or requiring bulk movement of water—don’t fit the description of diffusion.