Pollination, Fertilization, and Grain Development

In nature, the matnre seeds eventually shed from the plant and fall to the soil to wait for proper conditions for germination, thns reinitiating the life cycle. 

FIGURE 4.1 A schema of the typical flower of cereal grains and the ovary structure showing the ovum and polar nuclei that, upon fertilization, yield the germ and endosperm tissues. 

The aleurone layer differentiates from the rest of the starchy endosperm approximately 2 weeks after pollination. There is clear evidence that aleurone cells synthesize starch granules after fertilization however, the starch granules disappear and the cell walls thicken as the grain matures. The cytoplasm of aleurone cells contains phytic acid bodies, protein bodies, and spherosomes or fat depots. The aleurone ceU walls contain soluble and insoluble dietary fiber, phenolics such as ferulic acid, ara-binoxylans, and P-glucans that fluoresce when viewed under a microscope equipped with ultraviolet light. 

The endosperm cell walls start developing 3 to 5 days postanthesis. Cellulose is placed in cell walls starting in the periphery and gradually migrates to the central endosperm part. The mature cell walls of rice, maize, sorghum, and millets are thinner compared to wheat, barley, rye, and triticale. 

The germ takes more time to develop compared to the endosperm. The wheat embryonic axis is observed until approximately 23 days after anthesis. 

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