A Chitosan Starter Regimen Enhances Early Seedling Growth and Starch Granule Accumulation in Mung Bean (Vigna radiata L.)

Abstract

This study investigated the potential of chitosan as a natural biostimulant to promote early plant development and starch granule accumulation in tissues using mung bean (Vigna radiata L.) as the model. The effects of plant-derived chitosan (CS1) and animal-derived chitosan (CS2) were compared with chemical fertilizer and distilled water. Mung bean seeds were germinated on cotton wool and irrigated once daily for 8 days under four treatments (CS1, CS2, chemical fertilizer, and distilled water), with three replicates per treatment. Germination percentage and stem height were recorded to evaluate early growth performance. Starch accumulation was assessed by preparing transverse stem sections and staining with iodine to observe and estimate starch granule abundance under a microscope. Reducing sugar content was evaluated using Benedict’s test with a qualitative scale ranging from low to highest intensity (+ to ++++). In addition, a “starter regimen” was tested by applying animal-derived chitosan on Days 1–5 followed by chemical fertilizer on Days 6–8 to examine the use of chitosan as an initial treatment. The results showed that CS2 produced the highest germination percentage and promoted the greatest seedling growth by Day 8, with the overall ranking CS2 > chemical fertilizer > CS1 > distilled water. The preliminary reducing sugar assay indicated the strongest reaction in the CS2 group (++++), followed by CS1 (+++), chemical fertilizer (++), and distilled water (+). The mean starch granule counts (mean ± SD) decreased in the order CS2 (31.5 ± 3.5), CS1 (20.0 ± 2.0), chemical fertilizer (13.5 ± 1.5), and distilled water (6.0 ± 1.0). Notably, the “starter regimen” yielded the highest starch granule count (41.5 ± 1.5), exceeding all single-treatment conditions. Overall, these findings indicate that animal-derived chitosan enhances germination, seedling growth, and starch accumulation, and its use as an initial treatment followed by chemical fertilization further increases starch granule accumulation.