Are Lateral Roots of Tomato Spaced by Multiples of a Fundamental Distance?

Abstract

Roots of tomato (Lycopersicon esculentum Miller) were cultured in vitro for 8-16 d at the end of which period the number of daughter roots (first order laterals), and their distribution on the mother root axis, were recorded. It was observed that the daughter roots are distributed along the mother root in two series, and that their longitudinal distribution, in both series and in the total series, was non-random, in the sense of being systematically spaced out rather than systematically clustered. There was an approximately two-thirds probability that a daughter root would be on the opposite side of the root from its closest sister in the proximal direction, but this finding seemed explicable by the observed 'spaced-out' distribution in each series, without invoking any interaction between the two side series. Earlier, it had been suggested that distances between successive sister roots in a series are multiples of a quantum distance, probably because the daughter roots observed are a subset of a set of evenly spaced candidate root primordia, the rest of which are developmentally arrested. The sister-sister distances were analysed statistically for the presence of such a quantum. However, although some daughter root series showed a statistically significant quantal tendency, this did not seem to be a general feature of the mother roots.