CHEMICAL COMPONENTS FIG 3. 8 Scanning electron micrograph of maize starch granules of spherical and angular types. Some angular granules show indentations due to pressure from protein bodies endosperm constituents such as protein bodies. labelled precursors incorporated into growing granules(Badenhuizen, 1969). Such a system Pitting on the surface can be caused by enzymic of growth allows for the change in shape that hydrolysis and it is possible to find such granules occurs in starches of the Triticeae, by preferential in some cereal grains in which germination has deposition on some parts of the surface. As a begun or in which insect damage has occurred. result they change from tiny spheres to larger There is no evidence that these two physical lentil shaped granules(Evers, 1971) modifications to granule form change the chemical Some structures not evident in untreated granules can be revealed or exaggerated by treat As granules are transparent some manifesta- ment with weak acid or amylolytic enzymes. In tions of internal structure can be detected, even cereal starches a lamellate structure results if their significance cannot be fully appreciated. from removal of more susceptible layers and One such internal feature is the hilum exhibited persistence of more resistant layers. Layers may by granules of some species. It is a small air be spaced progressively more closely towards the space, considered to represent the point of initia- outside. The number of rings appears to coincide tion around which growth occurred(Hall and with the number of days for which a granule Sayre, 1969). This assumes that granules grow grows(Buttrose, 1962 ). Lamellae cannot be by deposition of new starch material on the outer revealed in granules from plants grown under surface of existing granules, and indeed this has. conditions of continuous illumination(Evers been demonstrated by detection of radioactively 1979CHEMICAL COMPONENTS 59 FiG 3.8 Scanning electron micrograph of maize starch granules of spherical and angular types. Some angular granules show indentations due to pressure from protein bodies. endosperm constituents such as protein bodies. (Fig. 3.8). Pitting on the surface can be caused by enzymic hydrolysis and it is possible to find such granules in some cereal grains in which germination has begun or in which insect damage has occurred. There is no evidence that these two physical modifications to granule form change the chemical properties of the granules. As granules are transparent some manifesta￾tions of internal structure can be detected, even if their significance cannot be fully appreciated. One such internal feature is the hilum exhibited by granules of some species. It is a small air￾space, considered to represent the point of initia￾tion around which growth occurred (Hall and Sayre, 1969). This assumes that granules grow by deposition of new starch material on the outer surface of existing granules, and indeed this has . been demonstrated by detection of radioactively labelled precursors incorporated into growing granules (Badenhuizen, 1969). Such a system of growth allows for the change in shape that occurs in starches of the Triticeae, by preferential deposition on some parts of the surface. As a result they change from tiny spheres to larger lentil shaped granules (Evers, 1971). Some structures not evident in untreated granules can be revealed or exaggerated by treat￾ment with weak acid or amylolytic enzymes. In cereal starches a lamellate structure results from removal of more susceptible layers and persistence of more resistant layers. Layers may be spaced progressively more closely towards the outside. The number of rings appears to coincide with the number of days for which a granule grows (Buttrose, 1962). Lamellae cannot be revealed in granules from plants grown under conditions of continuous illumination (Evers, 1979)