Plant Growth Regulators: Enhancing Mulberry Leaf Characteristics for Sustainable Sericulture

Abstract

Mulberry (Morus spp.) is the exclusive feeding source for the silkworm Bombyx mori, and its physiological and biochemical traits directly influence silkworm growth, cocoon yield, and silk quality. The productivity and nutritive value of mulberry leaves are governed not only by genotype and environment but also by endogenous plant hormones and exogenous growth regulators that coordinate growth, metabolism, and stress responses. Hormones such as auxins, cytokinins, gibberellins, abscisic acid, jasmonates, salicylic acid, and brassinosteroids regulate key processes including leaf expansion, chlorophyll stability, nutrient assimilation, and secondary metabolite accumulation. Exogenous application of growth regulators has been shown to enhance leaf biomass, improve protein and carbohydrate content, delay senescence, and mitigate abiotic stresses, thereby improving leaf quality for sericulture. Recent advances in molecular biology, omics technologies, nanotechnology, and biostimulant-based practices are providing new avenues to manipulate hormone pathways for sustainable mulberry improvement. This review integrates advances in understanding the hormonal regulation of mulberry physiology and biochemistry, critically evaluates outcomes of growth regulator interventions, and identifies innovative approaches to enhance resilience and sustainability in sericulture.