Observation and Investigation of Starch Granules Within Wheat Pericarp and Endosperm

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The pericarp and endosperm are two important wheat caryopsis sinks containing starch granules. In order to further clarify developmental characteristics of starch granules within wheat pericarp and endosperm, caryopses of hard and soft wheat at different days after pollination were used as experimental materials and their sections were observed with light and electron microscopy in this paper. The results indicated: (1) Pericarp parenchyma cells contained two types of starch granules: single-granule starch granules (ISG) and compound-granule starch granules (CSG). Pericarp parenchyma cells underwent degeneration from the part adjacent to cross cells to the part near the pericarp epidermis. Along with degeneration of pericarp parenchyma cells, CSG were transformed into ISG and all of ISG were gradually disintegrated. (2) There were denser chloroplasts present within the green pericarp cells around the vascular system in hard wheat than in soft wheat. (3) The tiny ISG appeared in aleurone cells at 9 days after pollination, but disappeared in the high-level differentiated aleurone cells. (4) ISG of the inner-layer endosperm transfer cells, sub-aleurone cells and the central starchy endosperm cells developed better in hard wheat than in soft wheat. This was probably because endosperm transfer cells had stronger nutrient transport function and the green pericarp cells provided more photosynthates for the endosperm in hard wheat than in soft wheat.