The relationship between grain weight and 0ther grain properties was investigated in four inbred lines of maize differing in seed size. Differences in final grain weight were, as expected, associated with parallel changes in rate and duration of grain filling. Increase in seed size was also dependent on a higher number of cells in the endosperm suggesting that endosperm cell number, more than cell size, plays an important role in controlling the final size of maize grain. Moreover, in the four inbreds investigated starch granule size and the level of three important enzymes involved in starch biosynthesis were not correlated to final grain weight. Among the inbreds studied Mo17, a line characterized by large seed size and high general combining ability, exhibited the highest level of sucrose synthase activity.

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