Application to endosperm hardness

In the high water content of the immature kernel, proteins and lipids compete for the starch granule surface. The granule surface would be expected to be less polar (more hydrophobic) than the aqueous medium. Puroindolines are hydrophobic proteins and would therefore tend to adsorb at the starch granule surface. By the mass action law, their amounts would be greatest in the wild phenotype (i.e., with both puroindolines present). 

The other factor to consider is the molecular weight. Puroindolines are rather small proteins. Other proteins in the kernel can reach very high molecular weights (e.g., glutenins) and thus have high free energies of adsorption. They could therefore replace pmoindolines at the starch surface. 

Students are supplied with numbered packets of wheat kernels (6-10 kernels) of known hardness (soft, hard, durum) and asked to classify them as soft, hard, or very hard. 

Write a paragraph about Table 4.1, attempting to explain why the different mutations induce a change from soft to hard kernels. 

Barlow, K. K., S. M. Buttrose, D. H. Simmonds, and M. Vesk. 1973. The nature of the starch protein interface in wheat endosperm. Cereal Chemistry 50 443—454. 

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