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.
1 To get the best head start, turn over your pea planting beds in the fall, add manure to the soil, and mulch well. 2  As with other legumes, pea roots will fix nitrogen in the soil, making it available for other plants.  Peas will appreciate a good sprinkling of wood ashes to the soil before planting.