What is the chemical uptake form of potassium?

The correct choice is the positively charged potassium ion, known as K+. This is the form in which potassium is taken up by plants through their root systems. Potassium is an essential macronutrient that plays a critical role in various physiological processes within plants, including enzyme activation, photosynthesis, and regulation of water uptake. The K+ ion is highly soluble in soil solution, making it readily available for absorption by plant roots.

In contrast, calcium (Ca2+), sodium (Na+), and magnesium (Mg2+) are also important nutrients but do not represent the chemical uptake form of potassium. Calcium and magnesium often play structural and signaling roles, while sodium, although sometimes taken up by plants, is not essential for all plant growth and can even be harmful in excessive amounts. Thus, K+ is the unique and specific form of potassium that plants utilize for growth and development.