What is one of the signs of a potassium deficiency in plants?

A potassium deficiency in plants typically manifests through the wilting and discoloration of older leaves. Potassium is an essential nutrient that plays a vital role in various physiological functions, including water regulation, enzyme activation, and photosynthesis. When plants lack sufficient potassium, they struggle to maintain turgor pressure in their cells, leading to wilting. Additionally, potassium is crucial for the synthesis of chlorophyll, so the older leaves may also start losing their green color, turning yellow or brown. This is especially notable in older leaves because they are often the first to show nutrient deficiencies as the plant prioritizes newer growth.

Other options do not accurately reflect the symptoms of potassium deficiency. Bright green color in leaves typically signals adequate or high levels of nitrogen rather than potassium. Rapid growth of young seedlings suggests optimal conditions for growth, which is not associated with a deficiency. Increased resistance to disease is generally an indicator of overall health and sufficient nutrient availability, which would not be seen in plants suffering from a potassium shortfall.