A new functional fertilizer containing 5-aminolevulinic acid promoted hydroponically-grown vegetables in the Netherlands

5-Aminolevulinic acid (5-ALA) is the key precursor in the biosynthesis of tetrapyrroles such as chlorophylls and hemes. 5-ALA is the unique precursor of tetrapyrroles. Iron element can activate 5-ALA-induced physiological actions. We conducted experiments of a new functional fertilizer including 5-ALA -HCI (0.3%), magnesium nitrate, Fe-DTPA, urea and the other mineral nutrients on the yield of paprika and strawberry fruits. Paprika and strawberry plants were transplanted in a rock-wool and a peat respectively, and they were weekly irrigated with a hydoroponic solution added with or without the fertilizer (paprika: 500-800 and strawberry: 500 ml ha(-1)) respectively. The cumulative fruit yield of paprika treated with the fertilizer increased by 4.3 to 9.0% of control. The nutrient solution analysis showed that NO3-N uptake by paprika plants with the fertilizer treatment was increased by 16% of control. The yield increase of paprika may be related partly to NO3-N uptake increase by the fertilizer treatment. The cumulative fruit yield of strawberry during 8 weeks after the treatment increased by 4.8% of control. Size of the fruit slightly decreased, in contrast, percentage of dry matter, sugar and citric acid contents significantly increased.