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The accumulation and morphology of starch in the pericarp, embryo and endosperm of normal and waxy maize were investigated using whole sections of complete caryopses. Pericarp starch took the form of compound granules, was distributed in the bottom of caryopses, and degraded from the top to the bottom. Embryo starch mostly took the form of simple granules and accumulated in the scutellum beginning approximately 10 DAP. In the endosperm, starch accumulated longitudinally from the top to the bottom and transversely from the centre to the periphery with caryopsis development. The peripheral endosperm cells synthesized starch faster than did the inner ones. Simple and compound starches were both observed, but the compound starch granules were distributed in the central region of the endosperm. At a late stage of development, compound starch was only observed in the bottom central portion of the endosperm. The pericarp starch of normal maize showed higher amylose content than did the embryo and endosperm starch. The waxy maize pericarp and embryo starches had similar amylose contents, but amylose was hardly detected in the endosperm due to the granule-bound starch synthase I gene mutation. The starches from the endosperm, embryo and pericarp of normal and waxy maize all had A-type crystallinity., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Highlights • Starch from vitreous endosperm (VS) was larger than that from floury endosperm (FS). • VS had higher amylose and damaged starch contents than FS. • VS had lower relative crystallinity and lamellar peak intensity than FS. • Native FS was more resistant to gelatinization and enzyme hydrolysis than VS. • Gelatinized and retrograded VS and FS had similar digestion properties. Abstract Starches were isolated from vitreous and floury endosperms from the same kernels, and their physicochemical properties were investigated to reveal their differences. Starch from vitreous endosperm had more surface indentations, larger granule size, and higher contents of protein, amylose and damaged starch than that from floury endosperm. Both starches from vitreous and floury endosperms exhibited A-type crystalline structure, but starch from vitreous endosperm had lower relative crystallinity and lamellar peak intensity than that from floury endosperm. Starch from floury endosperm had higher gelatinization temperature and enthalpy but lower gelatinization temperature range and percentage of retrogradation than that from vitreous endosperm. Native starch from floury endosperm was more resistant to enzyme hydrolysis than that from vitreous endosperm. Gelatinized and retrograded starches had similar digestion properties between starches from vitreous and floury endosperms. Principal component analysis indicated that starches from vitreous and floury endosperms had significant differences in their physicochemical properties. [ABSTRACT FROM AUTHOR]

The vitreous and floury endosperms have regional distributions in maize kernels, and influence their qualities and applications. In this study, the whole transverse and longitudinal sections of maize mature dent, flint, and pop kernels were observed to reveal and compare the morphological characteristics of cell, starch, and protein in different regions of endosperm. The shape and size of cells had significant differences in different regions of dent and flint maize endosperms, but had no relationship with vitreous and floury texture. Popcorn had homogeneously polygonal cells in whole endosperm. The vitreous endosperm in middle and central regions of kernel had polygonal starch granules with large size and that close to aleurone cells had spherical granules with small size, but the floury endosperm had only spherical granules with different sizes. The shape and size of starch granules did not directly determine the texture of vitreous and floury endosperm. The storage protein was distributed regionally in endosperm, and its content and spatial distribution was related with vitreous endosperm. The above results not only enriched our knowledge of vitreous and floury endosperms of maize, but also provided some information for quality breeding and applications of maize kernels with different vitreousness. • The whole sections were prepared in maize mature dent, flint and pop kernels. • Cell, starch and protein in different regions of endosperm were viewed and compared. • The shape and size of cells had no relationship with vitreous and floury endosperm. • Starch granules did not determine the texture of vitreous and floury endosperm. • The content and spatial distribution of protein was related with vitreous endosperm. [ABSTRACT FROM AUTHOR]