TRENDS OF EVOLUTIONARY CHANGES IN AMINO-ACID-COMPOSITION IN MONOCOTYLEDONOUS SEEDS

The amino acid composition of seeds in monocotyledons of 47 genera and 24 families was studied. According to this trait, the divergence of g rasses is comparable to that of all studied monocotyledonous families. Pronounced trends of changes were revealed for certain amino acids. I n monocotyledons (except grasses) it is the accumulation of arginine, while the changes in amino;acid composition in grasses are more divers e, sharing a common decrease in lysine and arginine content. A compari son of monocotyledons with a hypothetical ancestor of grasses using th e remoteness index (RT) suggests that many monocotyledonous families i nitially had an amino acid composition similar to that in the hypothet ical ancestor. Taking into account the immunochemical data on relation ships between monocotyledons and grasses, we have grounds to consider Arecaceae, Cyperaceae, and Juncaceae to be the most phylogenetically r elated to grasses.