Some sugars may stimulate seed germination and root elongation. Monosaccharides , which are aldehyde and ketone derivatives of the higher polyhydric alcohols. Oligosaccharides , a large group of polymeric carbohydrates consisting of a relatively few monosaccharide units. The class of organic compounds designated as lipids represents a convenient anlytical group rather than a specific type of compound. In normal aerobic soil the lipids probably exist largely as remnants of plant and microbial tissues.
Lipids are physiologically active.
Some compounds have a depressing effect on plant growth whereas others act as growth hormones. Waxes and similar materials may be responsible for the water repellent condition of certain sands. As mucoproteins As a muramic acid Amino acids, being readily decomposed by microorganisms, have only an ephemeral existence in soil. Thus the amounts present in the soil solution at any one time represent a balance between synthesis and destruction by microorganisms. The free amino acids content of the soil is strongly influenced by weather conditions, moisture status of the soil, type of plant and stage of growth, additions of organic residues, and cultural conditions.