Abstract
Growth of horizontally-grown Arabidopsis thaliana seedlings was almost half (0.57-fold) as compared to that of vertically-grown ones. Comparison of the root growth analysis ethylene mutants has showed that ethylene may play an important role in this process. The simplest explanation of growth inhibition is that mechanical and gravitropic stimulations affect continuously upon the horizontal root tips during the elongation, resulting in greater ethylene production. However, no significant difference was found in ethylene production between horizontal and vertical. In addition, the estimation of ethylene responsive genes by real-time PCR showed marked enhancement of the expression in horizontal roots; 5.2-fold for Ethylene Responsive Factor, ERF and 2.7-fold for basic chitinase, BACH, respectively. Relationship between the mechanical stimulation and the ethylene responsive genes will also be discussed briefly.
Plant physiologists, who often test biological activities of chemicals on filter paper, should pay much attention on potential blind spots of the common methodology.
