Amino Acids: Production by Plants and the Requirements of Man

Abstract

It is an interesting thought that plants, lacking brains, have a far greater capacity for organic synthesis than animals and humans. This fact underlies the different modes of nutrition of the two classes of organisms. Plants synthesise their fabric starting from simple inorganic precursors, i.e. they utilise an auxotrophic form of nutrition, whereas animals are heterotrophs and require preformed organic molecules, many of considerable chemical complexity, to be provided as components of their diet. This difference is seen most clearly in carbon and energy metabolism. Animals are utterly dependent upon plant photosynthesis for the conversion of solar into chemical forms of energy and for the production of the preformed carbon substrates necessary for their synthetic and respiratòry processes. A second major difference is encountered when nitrogen metabolic processes are compared. Plants produce the vast range of nitrogen compounds essential for their growth and development starting from inorganic sources of nitrogen absorbed by their root systems, but monogastric animals must obtain minimum quantities of many preformed organic nitrogen compounds in their diet. Man’s efforts over millenia to select and cultivate a range of plant species then may be seen not only as an attempt to stave off hunger but, less consciously, to ensure a reliable and sufficient supply of particular chemical substances.