1. Starch grains of endosperm of 766 grass species belonging to 244 genera have been examined. The starch grains are divided into four types. Type 1 represents simple grains which are broadly elliptic, elliptic-round, or rarely reniform. Starch grains of Type 2 are also simple, but they are hexagonal, pentagonal, round, or rarely rectangular. In Type 3, both simple and compound grains are included in the same seed. In Type 4, only compound grains are found throughout the endosperm.
2. Type 1 is found only in Triticeae,
Bromus and
Brachypodium. Type 2 is observed in most species of Panicoideae, some members of Eragrostoideae, Arundinoideae and Bambusoideae and
Brachyelytrum of Festucoideae. Some species of Panicoideae, Eragrostoideae and Arundinoideae have shown Type 3. Type 4 is most common in grasses, and is found in many species of Festucoideae, Eragrostoideae and Oryzoideae, and in some species of Panicoideae, Arundinoideae, and Bambusoideae.
3. Systematic significance of starch grains has been discussed. The differences between Types 2, 3 and 4 may be of minor value, as all of these types are sometimes found in species of the same genus. The difference between Type 1 and Type 4 seems to be systematically significant. According to the habitual division of the starch grains of grass endosperm into two types, simple and compound, the starch features can not be rightly used in the systematics.
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