Potassium activates plant enzymes and keeps cell fluid movement in balance. Potassium regulates water loss through stomata (tiny pores) on the leaves, and it is necessary for root formation and food storage in the plant. Severe deficiencies in vegetables can appear as deformed, stunted or yellow leaves, weak stems and premature fruit drop.
This corn shows severe potassium deficiency in the stunted, yellowed leaves. Stalks lack strength and fall over late in the season.
Poor flesh development in the two tomatoes on the left is caused by potassium deficiency. The two fruits on the right show normal development.
Potassium deficiency in young tomato plants results in deformed stems and leaves, browning in older leaves, ripe fruit falls off vines.