Plants need protein for healthy growth and development. One of the critical roles of protein in plants is regulating phototropism and mediating the response of plants to light-dark cycles. Proteins are also involved in energy-generating reactions, intracellular structure and membrane transport.
Proteins are made up of smaller building blocks called amino acids. Plants require about 20 amino acids in order to start protein synthesis and for plant growth to occur. Unlike animals that can derive amino acids by consuming plants and other organisms, plants depend hugely on soil nutrients for their protein supply.
Because nitrate is one of the main elements in protein, agricultural systems use nitrogen fertilizers to replenish nutrients in the soil and aid plants in generating needed proteins. The nitrates are converted into amino acids, synthesized into protein and stored in different places in the plant. Only a small percentage of nitrates, however, get absorbed by plants, and the remaining nitrogen leaches into either the soil, the air or water.
Protein deficiency in plants may lead to stunted growth, often characterized by light-green lower leaves or the yellowing of older leaves. Further deficiency may lead to the development of necrosis or brown discoloration and leaf tip death.