Which nutrient can enhance a plant's ability to tolerate drought and cold conditions?

Potassium is a crucial nutrient that plays a significant role in enhancing a plant's ability to withstand drought and cold conditions. It is involved in the regulation of water use within the plant, helping to maintain cell turgor pressure which is vital for maintaining structural integrity during periods of water scarcity. Potassium also helps to control the opening and closing of stomata, which are essential for gas exchange and transpiration. By improving the plant's water efficiency, potassium allows it to better manage stress brought on by drought.

In colder conditions, potassium contributes to overall plant health by supporting metabolic processes that enable the plant to adapt to low temperatures. Adequate potassium levels can promote better root development and improve overall plant vigor, making it better equipped to endure environmental stresses.

In contrast, phosphorus primarily supports root development and energy transfer processes, nitrogen is mainly associated with leafy growth and overall plant vigor, and sulfur is important for protein synthesis and enzyme function, but does not have the same direct impact on drought and cold tolerance as potassium does. Thus, potassium's unique qualities make it the key nutrient in enhancing drought and cold tolerance in plants.