Promotive effects of 5-aminolevulinic acid on the yield of several crops

The role of 5-aminolevulinic acid (ALA) as a precursor of chlorophyll or a herbicide is well documented. In the present report, to elucidate the physiological effects of ALA, this compound was applied to the foliage of radish at 0.06, 0.18, 0.6, 1.8 and 6 mM. ALA at 0.06-1.8 mM increased the dry weight of radish root (underground part), but injured radish seedlings at 6 mM. Also, the application of ALA at 0.18 and 0.6 mM increased fixation of CO2 in light and decreased release of CO2 in darkness. Furthermore, the effects of foliar treatment of ALA on the yield of several crops were also evaluated. The results showed that an application of ALA at low concentrations increased the growth and yield by 10-60% over the control on kidney bean, barley, potato and garlic. These results suggest that ALA has plant growth regulating properties at low concentrations and may enhance agricultural productivity.