Humic acid (HA) is a complex organic matter found in the environments, especially in grassland soils with a high density. The bioactivity of HA to promote plant growth depends largely on its extraction sources. The quality-control of HA and the quality improvements via an artificial synthesis are thus challenging. We recently reported that a polymeric product from fungal laccase-mediated oxidation of catechol and vanillic acid (CAVA) displays a HA-like activity to enhance seed germination and salt stress tolerance in a model plant, Arabidopsis. Here, we examined whether HA or CAVA enhances the growth of Italian ryegrass seedling. Height and fresh weight of the plant with foliar application of HA or CAVA were bigger than those with only water. Interestingly, enhanced root developments were also observed in spite of the foliar treatments of HA or CAVA. Finally, we proved that HA or CAVA promotes the regrowth of Italian ryegrass after cutting. Collectively, CAVA acts as a HA mimic in Italian ryegrass cultivation, and both as a biostimulant enhanced the early growth and regrowth after cutting of Italian ryegrass, which could improve the productivity of forage crops.

• Laila Khaleda(Division of Applied Life Science (BK21Plus), Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Research Institute of Life Sciences (RILS), Gyeongsang National University)
• Min Gab Kim(ollege of Pharmacy and Research Institute of Pharmaceutical Science, PMBBRC, Gyeongsang National University)
• Woe-Yeon Kim(Division of Applied Life Science (BK21Plus), Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Research Institute of Life Sciences (RILS), Gyeongsang National University, Department of Agricultural Chemistry and Food Science & Technology, Institute of Agriculture and Life Science (IALS), Gyeongsang National University)
• Jong-Rok Jeon(Department of Agricultural Chemistry and Food Science & Technology, Institute of Agriculture and Life Science (IALS), Gyeongsang National University)
• Joon-Yung Cha(Division of Applied Life Science (BK21Plus), Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Research Institute of Life Sciences (RILS), Gyeongsang National University) Corresponding author