Name a common biostimulant used to enhance root growth.

• A. Humic acid
• B. Seaweed extract (kelp extract)
• C. Nitrogen fertilizer
• D. Compost tea

Answer: (B)

Biostimulants enhance plant development by stimulating growth signals and improving nutrient uptake, which helps roots form and extend more effectively. A common biostimulant for promoting root growth is seaweed extract (kelp extract). These extracts supply natural plant hormones such as auxins and cytokinins, along with other bioactive compounds, betaines, and oligosaccharides that invigorate root initiation and elongation, especially in cuttings and young transplants. They also support stress resilience and can boost root-zone microbial activity, aiding nutrient availability and overall root development.

Humic acids act by improving soil structure and nutrient-holding capacity, supporting growth in a broader way rather than specifically driving root initiation. Compost tea introduces beneficial microbes and nutrients, which helps soil biology but its effect on root growth is more variable. A nitrogen fertilizer provides essential nutrients but is not a biostimulant and can favor shoot over root growth if used in excess.