A gardener applies ten times the recommended dose of fertilizer. By afternoon the crop leaves droop even though soil moisture is ample. Which explanation fits best?

Core Concept

Excess fertilizer can raise the concentration of nonpenetrating solutes in the soil solution enough to make the environment effectively hypertonic relative to root cells. Water then leaves cells by osmosis, vacuoles shrink, and turgor falls, causing wilting even when liquid water is present. Recovery requires reducing the external salt load and restoring favorable ion and water-potential gradients; plants may also export excess ions that entered root cells.