Abstract
Based on the hypothesis that phototropism is caused by an unequal distribution of blue light-induced growth inhibitors that inhibit the action of auxin on the illuminated and the shaded sides, not by auxin, some blue light-induced growth inhibitors were isolated and identified from many plant species. As the inhibitors in maize (Zea mays L.), DIMBOA and MBOA were isolated and identified by their spectral analyses. Determination of DIMBOA precursor (DIMBOA-glucoside), DIMBOA and MBOA levels during phototropic curvature and their bioassay indicated that phototropic stimulation induce the conversion of inactive DIMBOA-glucoside to the highest active DIMBOA, which plays an important role in the phototropism of maize coleoptiles, and then metabolizes into MBOA (lower activity), in the illuminated side. Recently, we found that the activity of β-glucosidase, which releases DIMBOA from DIMBOA-glucoside, was enhanced by blue illumination. In this study, we report the role of β-glucosidase on phototropism of maize coleoptiles.
