Plant form based on the pipe model theory II. Quantitative analysis of ramification in morphology

Ramification in tree structure was investigated by the main axis cutting method, which differs from the ordinary stratified clipping method. An axis running from the arbitrary terminal leader of the shoot to the stem base was termed the “main axis”. Cutting the main axis into pieces of constant length gives the “segment layer”, which consists of segments of the main axis and all branches and leaves diverging from the respective segments. There was a linear relationship between the weight of a main axis segment (in the range where leaves exist) of constant length and that of all the parts above the segment. Since plant form is determined by branches diverging regularly from the mother branch or stem, this linear relationship is considered to support the concept of the pipe model theory. It is also suggested that the proportionality constant of the linear relationship may specify the branching structure or ramifications of plant form.