Carboxyl groups have an electronegative oxygen atom double bonded to a carbon atom. This carbon-oxygen bond is very polar and the fact that its a double bond increases the polarity of the bond.
PEA agar, also referred to as Phenylethyl Alcohol Agar is a medium  used by microbiologists to grow microorganisms. The ingredient that  supplies nitrogen is casein. Making the world better, one answer at a time.
In the case of nitrogen, the recycling of nitrogen from dead to living plants is often the only source of nitrogen in the soil. To make plants grow faster, what you need to do is supply the elements that the plants need in readily available forms. That is the goal of fertilizer.Most fertilizers supply just nitrogen, phosphorus and potassium because the other chemicals are needed in much lower quantities and are generally available in most soils. Nitrogen, phosphorus and potassium availability is the big limit to growth. Nitrogen, phosphorus, potassium (a.k.a. potash) - The three macronutrients and the three elements you find in most packaged fertilizers. 2  Sulfur, calcium, and magnesium-Secondary nutrients. 3  Boron, cobalt, copper, iron, manganese, molybdenum and zinc-Micronutrients.