The seeds of Medicago truncatula have morphological features typical of dicotyledons, and are borne in a spine-covered spiral pod. The cotyledons are rich in protein (35-45%), the major storage molecule, accumulate ca. 10% lipids and only traces of starch. The most abundant proteins are homologous to the globulin storage proteins of other legumes. The remainder of the dry weight is mainly composed of cell wall material and complex polysaccharides of the Raffinose family. The seed contains a residual endosperm constituting about 10% of the final seed mass. The embryo acquires desiccation tolerance by 12 DAP and afterwards is capable of germinating. Metabolite profiling in the endosperm, seed coat and embryo along with global approaches, such as transcriptomics and proteomics, were used to allow the dissection of molecular processes underlying seed development. An in vitro culture system has been developed allowing comparison of cotyledon development with or without the surrounding maternal seed tissues. Mature seeds exhibit dormancy that can be overcome e.g., by scarifying the seed. Seed size, seed dormancy and pod morphology are characters varying greatly between Medicago species, and characterization of genetic variability for these traits within M. truncatula is underway in several laboratories.
In The Medicago truncatula Handbook. Pp. 1-23