Abstract
In this first of three lessons spanning the topic of Plant Nutrition, we examine primarily the energetics and mechanisms of nutrient uptake and transport. These processes are particularly well illustrated by an examination of the essential nutrient potassium (K), and the closely related element sodium (Na). We also examine the challenges associated with providing plants with sufficient K to support vigorous growth, and the detrimental effects of sodium accumulation in soils. Finally, we examine efforts to improve the salinity tolerance of crop plants.