SEED DEVELOPMENT IN A SHRUNKEN ENDOSPERM BARLEY MUTANT

Seg8 is one of eight barley (Hordeum vulgare L.) mutants whose endosperm development is affected by the maternal plant genotype. This study was initiated to determine the nature and onset of abnormal development to provide a basis for further studies aimed at understanding the mechanism of genetic control. Seed development and synthesis and accumulation of reserve substances were compared between seg8 and its normal counterpart, cv. Klages. Light microscopic examination showed that the mutant phenotype appeared as early as 4 d after anthesis (DAA), and seg8 grain dry weight was significantly lower than cv. Klages by 8 DAA. Grain cell number was significantly lower in seg8 by 8 DAA, indicating an early termination of cell division. The mutant had a lower starch concentration and higher sucrose concentration, also evident at 8 DAA. Rates of [14C]sucrose incorporation into starch in excised half seeds were similar in both genotypes at 2 and 4 DAA, but at 8 and 12 DAA seg8 had a lower rate. Total protein concentration was not significantly different between the two genotypes throughout endosperm development. These results indicate that the mutation affects cell division and starch accumulation prior to 8 DAA. It is not known if the reduction in starch biosynthesis and accumulation results from a reduced capacity for starch or a defect in starch biosynthesis. © 1991 Annals of Botany Company.