Which ion is primarily responsible for uptake of Zinc in plants?

The primary ion responsible for the uptake of zinc in plants is the zinc ion itself. Zinc is an essential micronutrient for plants, playing a crucial role in various physiological and biochemical processes, including enzyme function and protein synthesis. The uptake of zinc occurs largely through the root system where it is absorbed in the form of zinc ions (Zn²⁺).

Zinc ions are taken up by root cells through a process that often involves specific transporters or channels in the plasma membrane. These transporters are selective for zinc and facilitate its movement into the plant, where it is then utilized in many metabolic pathways.

In contrast, other options like nickel, manganous ion, and calcium ion do not play a primary role in the uptake of zinc. While nickel can be involved in plant metabolism and manganese serves as another important micronutrient, they do not facilitate or enhance the uptake of zinc. Calcium, being a macronutrient, is primarily involved in cell wall structure and signaling, but it does not directly contribute to zinc uptake. Therefore, the correct answer highlights the direct relationship between zinc ions and their uptake by plants.