Grain number, wheat yield, and bottling beer: An analysis

Grain number has long been considered to be a key determinant of yield in wheat crops and cultivars. In this paper, we argue that both yield and grain number are constrained by a crop's ability to gather resources. In this sense, grain numbers can be considered more as a consequence of yield than a determinant. We examine published literature on the effects of variations in development, light, nitrogen, and water supply on grain number determination and yield. We conclude that most of the variation in both grain number and yield is likely caused by variations in resource accumulation, particularly nitrogen, by the crop.