Effects of 5-aminolevulinic acid on growth of plant seedlings

Recently, we have found that 5-aminolevulinic acid (ALA) has plant growth regulating properties in lower concentrations besides herbicidal properties in higher concentrations. To clarify these properties, the influence of ALA under different application methods and their concentrations were examined using plant seedlings : rice, corn, kidney bean and radish. The results showed that the effects of ALA depended on the application method and their concentrations. The appropriate application of ALA increased the growth of seedlings to 110-150%, and the optimum concentrations were 0.1-1 ppm on a root soaking, 30-100 ppm on a foliar spray and 10-100 g/10 a on a soil treatment, respectively. Although herbicidal properties at high concentrations has been reported to be different among plant species, the difference of the promotive effects of ALA at low concentrations between monocotyledon and dicotyledon was found to be negligible in this study. Moreover, ALA was also an easy biodegradable substance in soil.