Negative correlations among yield components are wide spread among the major crop plants, particularly under various kinds of environmental stress. The correlations are believed to be developmental rather than genetic per se, and are postulated to be caused by genetically independent components, developing in a sequential pattern, that are free to vary in response to either 1) a limited constant input of metabolites, or 2) an oscillatory input of these substances such that input is limiting at critical stages in the developmental sequence.