What nutrient is present in the atmosphere as a gas, and is responsible for the vegetative growth and dark green color of the plant?

Nitrogen is the nutrient present in the atmosphere as a gas, making up about 78% of the Earth's atmosphere. It plays a crucial role in plant growth as a fundamental component of amino acids, proteins, and nucleic acids, which are essential for the development of plant tissues. Nitrogen is vital for vegetative growth and is responsible for the dark green color of plants, primarily because it is a key element in chlorophyll, the pigment that allows plants to photosynthesize. This process is essential for converting light energy into chemical energy, ultimately supporting growth and productivity.

While phosphorus, potassium, and magnesium are also important nutrients for plants, they are not present in the atmosphere as gases. Phosphorus is primarily found in soil and rock minerals, potassium is available in the soil, and magnesium is mainly absorbed from the soil solution. Each of these nutrients contributes to various aspects of plant growth and development, but nitrogen's gaseous form and its direct involvement in chlorophyll production make it distinctly responsible for enhancing vegetative growth and giving plants their characteristic dark green coloration.