Synergistic Effects of Combined Application of Plant Growth Hormones and Micronutrients on Mulberry Biomass and Leaf Protein Content
M. N. Chethan *
Department of Sericulture, College of Agriculture, UAS, GKVK, Bengaluru. Karnataka -560065, India.
S. Chandrashekhar
Department of Sericulture, College of Agriculture, UAS, GKVK, Bengaluru. Karnataka -560065, India.
M. S. Varun
Department of Sericulture, College of Agriculture, UAS, GKVK, Bengaluru. Karnataka -560065, India.
K. Ranganatha
Department of Sericulture, College of Agriculture, UAS, GKVK, Bengaluru. Karnataka -560065, India.
C. M. Mahesh
Department of Sericulture, College of Sericulture, Chintamani, UAS, GKVK, Bengaluru. Karnataka -563125, India.
R. Pulak
Research Extension Centre, Central Silk Board, Lakhimpur, Assam- 787 001, India.
M. Arun Kumar
Silkworm Seed Production Centre, Central Silk Board, Jorhat, Assam- 785 005, India.
*Author to whom correspondence should be addressed.
Abstract
Mulberry (Morus spp.) leaf biomass and protein content are primary determinants of silkworm growth, cocoon yield and raw silk quality. Conventional recommendations rely mainly on NPK fertilization, but in the last 3–4 decades many studies have evaluated plant growth regulators (PGRs / plant hormones) and micronutrient foliar sprays – often in combined commercial formulations – to improve mulberry productivity and nutritive value. Synthesizing the available work on mulberry, and supportive evidence from related crops, indicates that exogenous PGRs (auxins, gibberellins, cytokinins, triacontanol) and micronutrients (Fe, Zn, Mn, Cu, B, Mg) act synergistically to: (i) increase leaf area, shoot growth and total biomass, (ii) improve chlorophyll and photosynthetic efficiency, (iii) enhance nitrogen assimilation and soluble protein in leaves, and (iv) improve downstream silkworm performance. Triacontanol- and GA₃-based commercial foliar formulations that also contain multi-micronutrients (e.g. Seriboost, Plantonik, triacontanol–micronutrient mixtures) consistently show higher gains than either PGR or micronutrients alone, with 10–25% increases in leaf yield, improved leaf moisture and higher crude/soluble protein content in multiple field trials. However, dose–response relationships, variety-specific optimization, and detailed biochemical mechanisms in mulberry are not yet fully standardized.
Keywords: Mulberry, plant growth regulators, micronutrients, triacontanol, foliar spray, leaf protein, silkworm performance, sericulture