DIFFERENCES IN THE RATES OF METABOLISM OF VARIOUS TRIACYLGLYCEROLS DURING SEED-GERMINATION AND THE SUBSEQUENT GROWTH OF SEEDLINGS OF DIOSCOREA-TOKORO, A PERENNIAL HERB

Differences in the rates of metabolism of various triacylglycerols (TA Gs) in the reserve oil of seeds during the course of germination and s eedling growth were studied in Dioscorea tokoro, an East Asian perenni al herb, Eleven molecular species of TAG were determined in the reserv e oil of seeds, These TAGs contained five fatty acids: palmitic acid ( P); stearic acid (S); oleic acid (O); linoleic acid (L); and linolenic acid (Ln), At 20 degrees C, levels of TAGs with one or less than one L moiety, such as OLO, OOO, PLO, POO, OLS, and OLnO, decreased rapidly during germination and the initial elongation of seedlings, whereas l evels of other TAGs decreased slowly during the subsequent development of seedlings, Even though seeds were unable to germinate at these tem peratures, levels of some TAGs decreased during incubation at 5 degree s C and at 30 degrees C, Such changes might be related to the metaboli sm required fbr the survival of seeds at these temperatures, It is als o possible that they might be involved in the breaking of dormancy at low temperatures or in the induction of secondary dormancy at high tem peratures, The present results provide an example of the selective uti lization of the TAGs in the reserve oil of seeds during germination an d the subsequent growth of seedlings.