Screening of plant growth regulators acting on Arabidopsis thaliana.

Our screening system using Arabidopsis thaliana, enabled us to evaluate the effect of 38 known growth regulators on plant growth promotion. Eleven compounds in the study were found to show a promoting effect upon Arabidopsis dry weight and leaf number; in particular, oligosaccharides (OS) such as raffinose and stachyose had a marked effect. Detailed experiments indicated that the effect of OS on plant growth was not merely derived from its potential carbon source. Among the monosaccharides comprising stachyose, galactose showed the best promoting effect on plant growth.