Histochemical localization of storage components in caryopsis of rice (Oryza sativa L.)

Abstract

The pattern of distribution of major storage components of IR50 rice caryopsis was investigated and compared with several other cultivars and 17 wild species of Oryza. Starch occurs abundantly in the pericarp during early stages of grain filling. Starch begins to accumulate within the endosperm about 5 days after fertilization (DAF), and by 14 DAF starch in the pericarp is completely depleted, presumably transported as sucrose into the endosperm. Lipids are stored mostly in the aleurone cells. Proteins occur as aleurone grains and as discrete particles of three different sizes in the endosperm.80 percent of protein occurs in the subaleurone layers. The dead endosperm cells contain remnants of nuclear material. The rice embryo is rich in lipids and proteins and accumulates smaller amounts of starch. The aleurone and embryo also store phytin granules which contain abundant calcium, potassium and iron. The above pattern of distribution of major storage reserves is remarkably alike in all cultivars and species examined. The same pattern is also observed in grains stored for 12 years.