Allometric growth of Xanthium (Compositae) leaves

When Xanthium lamina width is plotted versus leaf length during the entire period of growth, a straight line is obtained representing an allometric relationship with a regression correlation coefficient of 0.9973 a lamina width to length ratio of 0.502 +/- 0.01 and chordare morphology. On the other hand, gibberellic acid neared plants yield a correlation coefficient of 0.9871 a lamina width to length ratio of 0.372 +/- 0.0074 and lanceolate leaves. The fraction of leaf width to leaf length is a measure of lamina width reduction. Gibberellic acid alters the mechanism which controls the balance between the leaf length and the leaf width.